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2022-12-01zram: preparation for multi-zcomp supportSergey Senozhatsky1-1/+1
Patch series "zram: Support multiple compression streams", v5. This series adds support for multiple compression streams. The main idea is that different compression algorithms have different characteristics and zram may benefit when it uses a combination of algorithms: a default algorithm that is faster but have lower compression rate and a secondary algorithm that can use higher compression rate at a price of slower compression/decompression. There are several use-case for this functionality: - huge pages re-compression: zstd or deflate can successfully compress huge pages (~50% of huge pages on my synthetic ChromeOS tests), IOW pages that lzo was not able to compress. - idle pages re-compression: idle/cold pages sit in the memory and we may reduce zsmalloc memory usage if we recompress those idle pages. Userspace has a number of ways to control the behavior and impact of zram recompression: what type of pages should be recompressed, size watermarks, etc. Please refer to documentation patch. This patch (of 13): The patch turns compression streams and compressor algorithm name struct zram members into arrays, so that we can have multiple compression streams support (in the next patches). The patch uses a rather explicit API for compressor selection: - Get primary (default) compression stream zcomp_stream_get(zram->comps[ZRAM_PRIMARY_COMP]) - Get secondary compression stream zcomp_stream_get(zram->comps[ZRAM_SECONDARY_COMP]) We use similar API for compression streams put(). At this point we always have just one compression stream, since CONFIG_ZRAM_MULTI_COMP is not yet defined. Link: https://lkml.kernel.org/r/20221109115047.2921851-1-senozhatsky@chromium.org Link: https://lkml.kernel.org/r/20221109115047.2921851-2-senozhatsky@chromium.org Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Minchan Kim <minchan@kernel.org> Cc: Nitin Gupta <ngupta@vflare.org> Cc: Suleiman Souhlal <suleiman@google.com> Cc: Nhat Pham <nphamcs@gmail.com> Cc: Alexey Romanov <avromanov@sberdevices.ru> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2020-05-28zram: Use local lock to protect per-CPU dataMike Galbraith1-0/+3
The zcomp driver uses per-CPU compression. The per-CPU data pointer is acquired with get_cpu_ptr() which implicitly disables preemption. It allocates memory inside the preempt disabled region which conflicts with the PREEMPT_RT semantics. Replace the implicit preemption control with an explicit local lock. This allows RT kernels to substitute it with a real per CPU lock, which serializes the access but keeps the code section preemptible. On non RT kernels this maps to preempt_disable() as before, i.e. no functional change. [bigeasy: Use local_lock(), description, drop reordering] Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20200527201119.1692513-8-bigeasy@linutronix.de
2020-05-28zram: Allocate struct zcomp_strm as per-CPU memorySebastian Andrzej Siewior1-1/+1
zcomp::stream is a per-CPU pointer, pointing to struct zcomp_strm which contains two pointers. Having struct zcomp_strm allocated directly as per-CPU memory would avoid one additional memory allocation and a pointer dereference. This also simplifies the addition of a local_lock to struct zcomp_strm. Allocate zcomp::stream directly as per-CPU memory. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Peter Zijlstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20200527201119.1692513-7-bigeasy@linutronix.de
2019-05-30treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152Thomas Gleixner1-5/+1
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-12-02zram: Convert to hotplug state machineAnna-Maria Gleixner1-2/+3
Install the callbacks via the state machine with multi instance support and let the core invoke the callbacks on the already online CPUs. [bigeasy: wire up the multi instance stuff] Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> Cc: Minchan Kim <minchan@kernel.org> Cc: rt@linutronix.de Cc: Nitin Gupta <ngupta@vflare.org> Link: http://lkml.kernel.org/r/20161126231350.10321-19-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-07-27zram: delete custom lzo/lz4Sergey Senozhatsky1-15/+0
Remove lzo/lz4 backends, we use crypto API now. [sergey.senozhatsky@gmail.com: zram-delete-custom-lzo-lz4-v3] Link: http://lkml.kernel.org/r/20160604024902.11778-6-sergey.senozhatsky@gmail.com Link: http://lkml.kernel.org/r/20160531122017.2878-7-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-27zram: switch to crypto compress APISergey Senozhatsky1-10/+7
We don't have an idle zstreams list anymore and our write path now works absolutely differently, preventing preemption during compression. This removes possibilities of read paths preempting writes at wrong places (which could badly affect the performance of both paths) and at the same time opens the door for a move from custom LZO/LZ4 compression backends implementation to a more generic one, using crypto compress API. Joonsoo Kim [1] attempted to do this a while ago, but faced with the need of introducing a new crypto API interface. The root cause was the fact that crypto API compression algorithms require a compression stream structure (in zram terminology) for both compression and decompression ops, while in reality only several of compression algorithms really need it. This resulted in a concept of context-less crypto API compression backends [2]. Both write and read paths, though, would have been executed with the preemption enabled, which in the worst case could have resulted in a decreased worst-case performance, e.g. consider the following case: CPU0 zram_write() spin_lock() take the last idle stream spin_unlock() << preempted >> zram_read() spin_lock() no idle streams spin_unlock() schedule() resuming zram_write compression() but it took me some time to realize that, and it took even longer to evolve zram and to make it ready for crypto API. The key turned out to be -- drop the idle streams list entirely. Without the idle streams list we are free to use compression algorithms that require compression stream for decompression (read), because streams are now placed in per-cpu data and each write path has to disable preemption for compression op, almost completely eliminating the aforementioned case (technically, we still have a small chance, because write path has a fast and a slow paths and the slow path is executed with the preemption enabled; but the frequency of failed fast path is too low). TEST ==== - 4 CPUs, x86_64 system - 3G zram, lzo - fio tests: read, randread, write, randwrite, rw, randrw test script [3] command: ZRAM_SIZE=3G LOG_SUFFIX=XXXX FIO_LOOPS=5 ./zram-fio-test.sh BASE PATCHED jobs1 READ: 2527.2MB/s 2482.7MB/s READ: 2102.7MB/s 2045.0MB/s WRITE: 1284.3MB/s 1324.3MB/s WRITE: 1080.7MB/s 1101.9MB/s READ: 430125KB/s 437498KB/s WRITE: 430538KB/s 437919KB/s READ: 399593KB/s 403987KB/s WRITE: 399910KB/s 404308KB/s jobs2 READ: 8133.5MB/s 7854.8MB/s READ: 7086.6MB/s 6912.8MB/s WRITE: 3177.2MB/s 3298.3MB/s WRITE: 2810.2MB/s 2871.4MB/s READ: 1017.6MB/s 1023.4MB/s WRITE: 1018.2MB/s 1023.1MB/s READ: 977836KB/s 984205KB/s WRITE: 979435KB/s 985814KB/s jobs3 READ: 13557MB/s 13391MB/s READ: 11876MB/s 11752MB/s WRITE: 4641.5MB/s 4682.1MB/s WRITE: 4164.9MB/s 4179.3MB/s READ: 1453.8MB/s 1455.1MB/s WRITE: 1455.1MB/s 1458.2MB/s READ: 1387.7MB/s 1395.7MB/s WRITE: 1386.1MB/s 1394.9MB/s jobs4 READ: 20271MB/s 20078MB/s READ: 18033MB/s 17928MB/s WRITE: 6176.8MB/s 6180.5MB/s WRITE: 5686.3MB/s 5705.3MB/s READ: 2009.4MB/s 2006.7MB/s WRITE: 2007.5MB/s 2004.9MB/s READ: 1929.7MB/s 1935.6MB/s WRITE: 1926.8MB/s 1932.6MB/s jobs5 READ: 18823MB/s 19024MB/s READ: 18968MB/s 19071MB/s WRITE: 6191.6MB/s 6372.1MB/s WRITE: 5818.7MB/s 5787.1MB/s READ: 2011.7MB/s 1981.3MB/s WRITE: 2011.4MB/s 1980.1MB/s READ: 1949.3MB/s 1935.7MB/s WRITE: 1940.4MB/s 1926.1MB/s jobs6 READ: 21870MB/s 21715MB/s READ: 19957MB/s 19879MB/s WRITE: 6528.4MB/s 6537.6MB/s WRITE: 6098.9MB/s 6073.6MB/s READ: 2048.6MB/s 2049.9MB/s WRITE: 2041.7MB/s 2042.9MB/s READ: 2013.4MB/s 1990.4MB/s WRITE: 2009.4MB/s 1986.5MB/s jobs7 READ: 21359MB/s 21124MB/s READ: 19746MB/s 19293MB/s WRITE: 6660.4MB/s 6518.8MB/s WRITE: 6211.6MB/s 6193.1MB/s READ: 2089.7MB/s 2080.6MB/s WRITE: 2085.8MB/s 2076.5MB/s READ: 2041.2MB/s 2052.5MB/s WRITE: 2037.5MB/s 2048.8MB/s jobs8 READ: 20477MB/s 19974MB/s READ: 18922MB/s 18576MB/s WRITE: 6851.9MB/s 6788.3MB/s WRITE: 6407.7MB/s 6347.5MB/s READ: 2134.8MB/s 2136.1MB/s WRITE: 2132.8MB/s 2134.4MB/s READ: 2074.2MB/s 2069.6MB/s WRITE: 2087.3MB/s 2082.4MB/s jobs9 READ: 19797MB/s 19994MB/s READ: 18806MB/s 18581MB/s WRITE: 6878.7MB/s 6822.7MB/s WRITE: 6456.8MB/s 6447.2MB/s READ: 2141.1MB/s 2154.7MB/s WRITE: 2144.4MB/s 2157.3MB/s READ: 2084.1MB/s 2085.1MB/s WRITE: 2091.5MB/s 2092.5MB/s jobs10 READ: 19794MB/s 19784MB/s READ: 18794MB/s 18745MB/s WRITE: 6984.4MB/s 6676.3MB/s WRITE: 6532.3MB/s 6342.7MB/s READ: 2150.6MB/s 2155.4MB/s WRITE: 2156.8MB/s 2161.5MB/s READ: 2106.4MB/s 2095.6MB/s WRITE: 2109.7MB/s 2098.4MB/s BASE PATCHED jobs1 perfstat stalled-cycles-frontend 102,480,595,419 ( 41.53%) 114,508,864,804 ( 46.92%) stalled-cycles-backend 51,941,417,832 ( 21.05%) 46,836,112,388 ( 19.19%) instructions 283,612,054,215 ( 1.15) 283,918,134,959 ( 1.16) branches 56,372,560,385 ( 724.923) 56,449,814,753 ( 733.766) branch-misses 374,826,000 ( 0.66%) 326,935,859 ( 0.58%) jobs2 perfstat stalled-cycles-frontend 155,142,745,777 ( 40.99%) 164,170,979,198 ( 43.82%) stalled-cycles-backend 70,813,866,387 ( 18.71%) 66,456,858,165 ( 17.74%) instructions 463,436,648,173 ( 1.22) 464,221,890,191 ( 1.24) branches 91,088,733,902 ( 760.088) 91,278,144,546 ( 769.133) branch-misses 504,460,363 ( 0.55%) 394,033,842 ( 0.43%) jobs3 perfstat stalled-cycles-frontend 201,300,397,212 ( 39.84%) 223,969,902,257 ( 44.44%) stalled-cycles-backend 87,712,593,974 ( 17.36%) 81,618,888,712 ( 16.19%) instructions 642,869,545,023 ( 1.27) 644,677,354,132 ( 1.28) branches 125,724,560,594 ( 690.682) 126,133,159,521 ( 694.542) branch-misses 527,941,798 ( 0.42%) 444,782,220 ( 0.35%) jobs4 perfstat stalled-cycles-frontend 246,701,197,429 ( 38.12%) 280,076,030,886 ( 43.29%) stalled-cycles-backend 119,050,341,112 ( 18.40%) 110,955,641,671 ( 17.15%) instructions 822,716,962,127 ( 1.27) 825,536,969,320 ( 1.28) branches 160,590,028,545 ( 688.614) 161,152,996,915 ( 691.068) branch-misses 650,295,287 ( 0.40%) 550,229,113 ( 0.34%) jobs5 perfstat stalled-cycles-frontend 298,958,462,516 ( 38.30%) 344,852,200,358 ( 44.16%) stalled-cycles-backend 137,558,742,122 ( 17.62%) 129,465,067,102 ( 16.58%) instructions 1,005,714,688,752 ( 1.29) 1,007,657,999,432 ( 1.29) branches 195,988,773,962 ( 697.730) 196,446,873,984 ( 700.319) branch-misses 695,818,940 ( 0.36%) 624,823,263 ( 0.32%) jobs6 perfstat stalled-cycles-frontend 334,497,602,856 ( 36.71%) 387,590,419,779 ( 42.38%) stalled-cycles-backend 163,539,365,335 ( 17.95%) 152,640,193,639 ( 16.69%) instructions 1,184,738,177,851 ( 1.30) 1,187,396,281,677 ( 1.30) branches 230,592,915,640 ( 702.902) 231,253,802,882 ( 702.356) branch-misses 747,934,786 ( 0.32%) 643,902,424 ( 0.28%) jobs7 perfstat stalled-cycles-frontend 396,724,684,187 ( 37.71%) 460,705,858,952 ( 43.84%) stalled-cycles-backend 188,096,616,496 ( 17.88%) 175,785,787,036 ( 16.73%) instructions 1,364,041,136,608 ( 1.30) 1,366,689,075,112 ( 1.30) branches 265,253,096,936 ( 700.078) 265,890,524,883 ( 702.839) branch-misses 784,991,589 ( 0.30%) 729,196,689 ( 0.27%) jobs8 perfstat stalled-cycles-frontend 440,248,299,870 ( 36.92%) 509,554,793,816 ( 42.46%) stalled-cycles-backend 222,575,930,616 ( 18.67%) 213,401,248,432 ( 17.78%) instructions 1,542,262,045,114 ( 1.29) 1,545,233,932,257 ( 1.29) branches 299,775,178,439 ( 697.666) 300,528,458,505 ( 694.769) branch-misses 847,496,084 ( 0.28%) 748,794,308 ( 0.25%) jobs9 perfstat stalled-cycles-frontend 506,269,882,480 ( 37.86%) 592,798,032,820 ( 44.43%) stalled-cycles-backend 253,192,498,861 ( 18.93%) 233,727,666,185 ( 17.52%) instructions 1,721,985,080,913 ( 1.29) 1,724,666,236,005 ( 1.29) branches 334,517,360,255 ( 694.134) 335,199,758,164 ( 697.131) branch-misses 873,496,730 ( 0.26%) 815,379,236 ( 0.24%) jobs10 perfstat stalled-cycles-frontend 549,063,363,749 ( 37.18%) 651,302,376,662 ( 43.61%) stalled-cycles-backend 281,680,986,810 ( 19.07%) 277,005,235,582 ( 18.55%) instructions 1,901,859,271,180 ( 1.29) 1,906,311,064,230 ( 1.28) branches 369,398,536,153 ( 694.004) 370,527,696,358 ( 688.409) branch-misses 967,929,335 ( 0.26%) 890,125,056 ( 0.24%) BASE PATCHED seconds elapsed 79.421641008 78.735285546 seconds elapsed 61.471246133 60.869085949 seconds elapsed 62.317058173 62.224188495 seconds elapsed 60.030739363 60.081102518 seconds elapsed 74.070398362 74.317582865 seconds elapsed 84.985953007 85.414364176 seconds elapsed 97.724553255 98.173311344 seconds elapsed 109.488066758 110.268399318 seconds elapsed 122.768189405 122.967164498 seconds elapsed 135.130035105 136.934770801 On my other system (8 x86_64 CPUs, short version of test results): BASE PATCHED seconds elapsed 19.518065994 19.806320662 seconds elapsed 15.172772749 15.594718291 seconds elapsed 13.820925970 13.821708564 seconds elapsed 13.293097816 14.585206405 seconds elapsed 16.207284118 16.064431606 seconds elapsed 17.958376158 17.771825767 seconds elapsed 19.478009164 19.602961508 seconds elapsed 21.347152811 21.352318709 seconds elapsed 24.478121126 24.171088735 seconds elapsed 26.865057442 26.767327618 So performance-wise the numbers are quite similar. Also update zcomp interface to be more aligned with the crypto API. [1] http://marc.info/?l=linux-kernel&m=144480832108927&w=2 [2] http://marc.info/?l=linux-kernel&m=145379613507518&w=2 [3] https://github.com/sergey-senozhatsky/zram-perf-test Link: http://lkml.kernel.org/r/20160531122017.2878-3-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Minchan Kim <minchan@kernel.org> Suggested-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-27zram: rename zstrm find-release functionsSergey Senozhatsky1-2/+2
This has started as a 'add zlib support' work, but after some thinking I saw no blockers for a bigger change -- a switch to crypto API. We don't have an idle zstreams list anymore and our write path now works absolutely differently, preventing preemption during compression. This removes possibilities of read paths preempting writes at wrong places and opens the door for a move from custom LZO/LZ4 compression backends implementation to a more generic one, using crypto compress API. This patch set also eliminates the need of a new context-less crypto API interface, which was quite hard to sell, so we can move along faster. benchmarks: (x86_64, 4GB, zram-perf script) perf reported run-time fio (max jobs=3). I performed fio test with the increasing number of parallel jobs (max to 3) on a 3G zram device, using `static' data and the following crypto comp algorithms: 842, deflate, lz4, lz4hc, lzo the output was: - test running time (which can tell us what algorithms performs faster) and - zram mm_stat (which tells the compressed memory size, max used memory, etc). It's just for information. for example, LZ4HC has twice the running time of LZO, but the compressed memory size is: 23592960 vs 34603008 bytes. test-fio-zram-842 197.907655282 seconds time elapsed 201.623142884 seconds time elapsed 226.854291345 seconds time elapsed test-fio-zram-DEFLATE 253.259516155 seconds time elapsed 258.148563401 seconds time elapsed 290.251909365 seconds time elapsed test-fio-zram-LZ4 27.022598717 seconds time elapsed 29.580522717 seconds time elapsed 33.293463430 seconds time elapsed test-fio-zram-LZ4HC 56.393954615 seconds time elapsed 74.904659747 seconds time elapsed 101.940998564 seconds time elapsed test-fio-zram-LZO 28.155948075 seconds time elapsed 30.390036330 seconds time elapsed 34.455773159 seconds time elapsed zram mm_stat-s (max fio jobs=3) test-fio-zram-842 mm_stat (jobs1): 3221225472 673185792 690266112 0 690266112 0 0 mm_stat (jobs2): 3221225472 673185792 690266112 0 690266112 0 0 mm_stat (jobs3): 3221225472 673185792 690266112 0 690266112 0 0 test-fio-zram-DEFLATE mm_stat (jobs1): 3221225472 24379392 37761024 0 37761024 0 0 mm_stat (jobs2): 3221225472 24379392 37761024 0 37761024 0 0 mm_stat (jobs3): 3221225472 24379392 37761024 0 37761024 0 0 test-fio-zram-LZ4 mm_stat (jobs1): 3221225472 23592960 37761024 0 37761024 0 0 mm_stat (jobs2): 3221225472 23592960 37761024 0 37761024 0 0 mm_stat (jobs3): 3221225472 23592960 37761024 0 37761024 0 0 test-fio-zram-LZ4HC mm_stat (jobs1): 3221225472 23592960 37761024 0 37761024 0 0 mm_stat (jobs2): 3221225472 23592960 37761024 0 37761024 0 0 mm_stat (jobs3): 3221225472 23592960 37761024 0 37761024 0 0 test-fio-zram-LZO mm_stat (jobs1): 3221225472 34603008 50335744 0 50335744 0 0 mm_stat (jobs2): 3221225472 34603008 50335744 0 50335744 0 0 mm_stat (jobs3): 3221225472 34603008 50335744 0 50339840 0 0 This patch (of 8): We don't perform any zstream idle list lookup anymore, so zcomp_strm_find()/zcomp_strm_release() names are not representative. Rename to zcomp_stream_get()/zcomp_stream_put(). Link: http://lkml.kernel.org/r/20160531122017.2878-2-sergey.senozhatsky@gmail.com Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-21zram: user per-cpu compression streamsSergey Senozhatsky1-11/+3
Remove idle streams list and keep compression streams in per-cpu data. This removes two contented spin_lock()/spin_unlock() calls from write path and also prevent write OP from being preempted while holding the compression stream, which can cause slow downs. For instance, let's assume that we have N cpus and N-2 max_comp_streams.TASK1 owns the last idle stream, TASK2-TASK3 come in with the write requests: TASK1 TASK2 TASK3 zram_bvec_write() spin_lock find stream spin_unlock compress <<preempted>> zram_bvec_write() spin_lock find stream spin_unlock no_stream schedule zram_bvec_write() spin_lock find_stream spin_unlock no_stream schedule spin_lock release stream spin_unlock wake up TASK2 not only TASK2 and TASK3 will not get the stream, TASK1 will be preempted in the middle of its operation; while we would prefer it to finish compression and release the stream. Test environment: x86_64, 4 CPU box, 3G zram, lzo The following fio tests were executed: read, randread, write, randwrite, rw, randrw with the increasing number of jobs from 1 to 10. 4 streams 8 streams per-cpu =========================================================== jobs1 READ: 2520.1MB/s 2566.5MB/s 2491.5MB/s READ: 2102.7MB/s 2104.2MB/s 2091.3MB/s WRITE: 1355.1MB/s 1320.2MB/s 1378.9MB/s WRITE: 1103.5MB/s 1097.2MB/s 1122.5MB/s READ: 434013KB/s 435153KB/s 439961KB/s WRITE: 433969KB/s 435109KB/s 439917KB/s READ: 403166KB/s 405139KB/s 403373KB/s WRITE: 403223KB/s 405197KB/s 403430KB/s jobs2 READ: 7958.6MB/s 8105.6MB/s 8073.7MB/s READ: 6864.9MB/s 6989.8MB/s 7021.8MB/s WRITE: 2438.1MB/s 2346.9MB/s 3400.2MB/s WRITE: 1994.2MB/s 1990.3MB/s 2941.2MB/s READ: 981504KB/s 973906KB/s 1018.8MB/s WRITE: 981659KB/s 974060KB/s 1018.1MB/s READ: 937021KB/s 938976KB/s 987250KB/s WRITE: 934878KB/s 936830KB/s 984993KB/s jobs3 READ: 13280MB/s 13553MB/s 13553MB/s READ: 11534MB/s 11785MB/s 11755MB/s WRITE: 3456.9MB/s 3469.9MB/s 4810.3MB/s WRITE: 3029.6MB/s 3031.6MB/s 4264.8MB/s READ: 1363.8MB/s 1362.6MB/s 1448.9MB/s WRITE: 1361.9MB/s 1360.7MB/s 1446.9MB/s READ: 1309.4MB/s 1310.6MB/s 1397.5MB/s WRITE: 1307.4MB/s 1308.5MB/s 1395.3MB/s jobs4 READ: 20244MB/s 20177MB/s 20344MB/s READ: 17886MB/s 17913MB/s 17835MB/s WRITE: 4071.6MB/s 4046.1MB/s 6370.2MB/s WRITE: 3608.9MB/s 3576.3MB/s 5785.4MB/s READ: 1824.3MB/s 1821.6MB/s 1997.5MB/s WRITE: 1819.8MB/s 1817.4MB/s 1992.5MB/s READ: 1765.7MB/s 1768.3MB/s 1937.3MB/s WRITE: 1767.5MB/s 1769.1MB/s 1939.2MB/s jobs5 READ: 18663MB/s 18986MB/s 18823MB/s READ: 16659MB/s 16605MB/s 16954MB/s WRITE: 3912.4MB/s 3888.7MB/s 6126.9MB/s WRITE: 3506.4MB/s 3442.5MB/s 5519.3MB/s READ: 1798.2MB/s 1746.5MB/s 1935.8MB/s WRITE: 1792.7MB/s 1740.7MB/s 1929.1MB/s READ: 1727.6MB/s 1658.2MB/s 1917.3MB/s WRITE: 1726.5MB/s 1657.2MB/s 1916.6MB/s jobs6 READ: 21017MB/s 20922MB/s 21162MB/s READ: 19022MB/s 19140MB/s 18770MB/s WRITE: 3968.2MB/s 4037.7MB/s 6620.8MB/s WRITE: 3643.5MB/s 3590.2MB/s 6027.5MB/s READ: 1871.8MB/s 1880.5MB/s 2049.9MB/s WRITE: 1867.8MB/s 1877.2MB/s 2046.2MB/s READ: 1755.8MB/s 1710.3MB/s 1964.7MB/s WRITE: 1750.5MB/s 1705.9MB/s 1958.8MB/s jobs7 READ: 21103MB/s 20677MB/s 21482MB/s READ: 18522MB/s 18379MB/s 19443MB/s WRITE: 4022.5MB/s 4067.4MB/s 6755.9MB/s WRITE: 3691.7MB/s 3695.5MB/s 5925.6MB/s READ: 1841.5MB/s 1933.9MB/s 2090.5MB/s WRITE: 1842.7MB/s 1935.3MB/s 2091.9MB/s READ: 1832.4MB/s 1856.4MB/s 1971.5MB/s WRITE: 1822.3MB/s 1846.2MB/s 1960.6MB/s jobs8 READ: 20463MB/s 20194MB/s 20862MB/s READ: 18178MB/s 17978MB/s 18299MB/s WRITE: 4085.9MB/s 4060.2MB/s 7023.8MB/s WRITE: 3776.3MB/s 3737.9MB/s 6278.2MB/s READ: 1957.6MB/s 1944.4MB/s 2109.5MB/s WRITE: 1959.2MB/s 1946.2MB/s 2111.4MB/s READ: 1900.6MB/s 1885.7MB/s 2082.1MB/s WRITE: 1896.2MB/s 1881.4MB/s 2078.3MB/s jobs9 READ: 19692MB/s 19734MB/s 19334MB/s READ: 17678MB/s 18249MB/s 17666MB/s WRITE: 4004.7MB/s 4064.8MB/s 6990.7MB/s WRITE: 3724.7MB/s 3772.1MB/s 6193.6MB/s READ: 1953.7MB/s 1967.3MB/s 2105.6MB/s WRITE: 1953.4MB/s 1966.7MB/s 2104.1MB/s READ: 1860.4MB/s 1897.4MB/s 2068.5MB/s WRITE: 1858.9MB/s 1895.9MB/s 2066.8MB/s jobs10 READ: 19730MB/s 19579MB/s 19492MB/s READ: 18028MB/s 18018MB/s 18221MB/s WRITE: 4027.3MB/s 4090.6MB/s 7020.1MB/s WRITE: 3810.5MB/s 3846.8MB/s 6426.8MB/s READ: 1956.1MB/s 1994.6MB/s 2145.2MB/s WRITE: 1955.9MB/s 1993.5MB/s 2144.8MB/s READ: 1852.8MB/s 1911.6MB/s 2075.8MB/s WRITE: 1855.7MB/s 1914.6MB/s 2078.1MB/s perf stat 4 streams 8 streams per-cpu ==================================================================================================================== jobs1 stalled-cycles-frontend 23,174,811,209 ( 38.21%) 23,220,254,188 ( 38.25%) 23,061,406,918 ( 38.34%) stalled-cycles-backend 11,514,174,638 ( 18.98%) 11,696,722,657 ( 19.27%) 11,370,852,810 ( 18.90%) instructions 73,925,005,782 ( 1.22) 73,903,177,632 ( 1.22) 73,507,201,037 ( 1.22) branches 14,455,124,835 ( 756.063) 14,455,184,779 ( 755.281) 14,378,599,509 ( 758.546) branch-misses 69,801,336 ( 0.48%) 80,225,529 ( 0.55%) 72,044,726 ( 0.50%) jobs2 stalled-cycles-frontend 49,912,741,782 ( 46.11%) 50,101,189,290 ( 45.95%) 32,874,195,633 ( 35.11%) stalled-cycles-backend 27,080,366,230 ( 25.02%) 27,949,970,232 ( 25.63%) 16,461,222,706 ( 17.58%) instructions 122,831,629,690 ( 1.13) 122,919,846,419 ( 1.13) 121,924,786,775 ( 1.30) branches 23,725,889,239 ( 692.663) 23,733,547,140 ( 688.062) 23,553,950,311 ( 794.794) branch-misses 90,733,041 ( 0.38%) 96,320,895 ( 0.41%) 84,561,092 ( 0.36%) jobs3 stalled-cycles-frontend 66,437,834,608 ( 45.58%) 63,534,923,344 ( 43.69%) 42,101,478,505 ( 33.19%) stalled-cycles-backend 34,940,799,661 ( 23.97%) 34,774,043,148 ( 23.91%) 21,163,324,388 ( 16.68%) instructions 171,692,121,862 ( 1.18) 171,775,373,044 ( 1.18) 170,353,542,261 ( 1.34) branches 32,968,962,622 ( 628.723) 32,987,739,894 ( 630.512) 32,729,463,918 ( 717.027) branch-misses 111,522,732 ( 0.34%) 110,472,894 ( 0.33%) 99,791,291 ( 0.30%) jobs4 stalled-cycles-frontend 98,741,701,675 ( 49.72%) 94,797,349,965 ( 47.59%) 54,535,655,381 ( 33.53%) stalled-cycles-backend 54,642,609,615 ( 27.51%) 55,233,554,408 ( 27.73%) 27,882,323,541 ( 17.14%) instructions 220,884,807,851 ( 1.11) 220,930,887,273 ( 1.11) 218,926,845,851 ( 1.35) branches 42,354,518,180 ( 592.105) 42,362,770,587 ( 590.452) 41,955,552,870 ( 716.154) branch-misses 138,093,449 ( 0.33%) 131,295,286 ( 0.31%) 121,794,771 ( 0.29%) jobs5 stalled-cycles-frontend 116,219,747,212 ( 48.14%) 110,310,397,012 ( 46.29%) 66,373,082,723 ( 33.70%) stalled-cycles-backend 66,325,434,776 ( 27.48%) 64,157,087,914 ( 26.92%) 32,999,097,299 ( 16.76%) instructions 270,615,008,466 ( 1.12) 270,546,409,525 ( 1.14) 268,439,910,948 ( 1.36) branches 51,834,046,557 ( 599.108) 51,811,867,722 ( 608.883) 51,412,576,077 ( 729.213) branch-misses 158,197,086 ( 0.31%) 142,639,805 ( 0.28%) 133,425,455 ( 0.26%) jobs6 stalled-cycles-frontend 138,009,414,492 ( 48.23%) 139,063,571,254 ( 48.80%) 75,278,568,278 ( 32.80%) stalled-cycles-backend 79,211,949,650 ( 27.68%) 79,077,241,028 ( 27.75%) 37,735,797,899 ( 16.44%) instructions 319,763,993,731 ( 1.12) 319,937,782,834 ( 1.12) 316,663,600,784 ( 1.38) branches 61,219,433,294 ( 595.056) 61,250,355,540 ( 598.215) 60,523,446,617 ( 733.706) branch-misses 169,257,123 ( 0.28%) 154,898,028 ( 0.25%) 141,180,587 ( 0.23%) jobs7 stalled-cycles-frontend 162,974,812,119 ( 49.20%) 159,290,061,987 ( 48.43%) 88,046,641,169 ( 33.21%) stalled-cycles-backend 92,223,151,661 ( 27.84%) 91,667,904,406 ( 27.87%) 44,068,454,971 ( 16.62%) instructions 369,516,432,430 ( 1.12) 369,361,799,063 ( 1.12) 365,290,380,661 ( 1.38) branches 70,795,673,950 ( 594.220) 70,743,136,124 ( 597.876) 69,803,996,038 ( 732.822) branch-misses 181,708,327 ( 0.26%) 165,767,821 ( 0.23%) 150,109,797 ( 0.22%) jobs8 stalled-cycles-frontend 185,000,017,027 ( 49.30%) 182,334,345,473 ( 48.37%) 99,980,147,041 ( 33.26%) stalled-cycles-backend 105,753,516,186 ( 28.18%) 107,937,830,322 ( 28.63%) 51,404,177,181 ( 17.10%) instructions 418,153,161,055 ( 1.11) 418,308,565,828 ( 1.11) 413,653,475,581 ( 1.38) branches 80,035,882,398 ( 592.296) 80,063,204,510 ( 589.843) 79,024,105,589 ( 730.530) branch-misses 199,764,528 ( 0.25%) 177,936,926 ( 0.22%) 160,525,449 ( 0.20%) jobs9 stalled-cycles-frontend 210,941,799,094 ( 49.63%) 204,714,679,254 ( 48.55%) 114,251,113,756 ( 33.96%) stalled-cycles-backend 122,640,849,067 ( 28.85%) 122,188,553,256 ( 28.98%) 58,360,041,127 ( 17.35%) instructions 468,151,025,415 ( 1.10) 467,354,869,323 ( 1.11) 462,665,165,216 ( 1.38) branches 89,657,067,510 ( 585.628) 89,411,550,407 ( 588.990) 88,360,523,943 ( 730.151) branch-misses 218,292,301 ( 0.24%) 191,701,247 ( 0.21%) 178,535,678 ( 0.20%) jobs10 stalled-cycles-frontend 233,595,958,008 ( 49.81%) 227,540,615,689 ( 49.11%) 160,341,979,938 ( 43.07%) stalled-cycles-backend 136,153,676,021 ( 29.03%) 133,635,240,742 ( 28.84%) 65,909,135,465 ( 17.70%) instructions 517,001,168,497 ( 1.10) 516,210,976,158 ( 1.11) 511,374,038,613 ( 1.37) branches 98,911,641,329 ( 585.796) 98,700,069,712 ( 591.583) 97,646,761,028 ( 728.712) branch-misses 232,341,823 ( 0.23%) 199,256,308 ( 0.20%) 183,135,268 ( 0.19%) per-cpu streams tend to cause significantly less stalled cycles; execute less branches and hit less branch-misses. perf stat reported execution time 4 streams 8 streams per-cpu ==================================================================== jobs1 seconds elapsed 20.909073870 20.875670495 20.817838540 jobs2 seconds elapsed 18.529488399 18.720566469 16.356103108 jobs3 seconds elapsed 18.991159531 18.991340812 16.766216066 jobs4 seconds elapsed 19.560643828 19.551323547 16.246621715 jobs5 seconds elapsed 24.746498464 25.221646740 20.696112444 jobs6 seconds elapsed 28.258181828 28.289765505 22.885688857 jobs7 seconds elapsed 32.632490241 31.909125381 26.272753738 jobs8 seconds elapsed 35.651403851 36.027596308 29.108024711 jobs9 seconds elapsed 40.569362365 40.024227989 32.898204012 jobs10 seconds elapsed 44.673112304 43.874898137 35.632952191 Please see Link: http://marc.info/?l=linux-kernel&m=146166970727530 Link: http://marc.info/?l=linux-kernel&m=146174716719650 for more test results (under low memory conditions). Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Suggested-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-01-15zram: pass gfp from zcomp frontend to backendMinchan Kim1-1/+1
Each zcomp backend uses own gfp flag but it's pointless because the context they could be called is driven by upper layer(ie, zcomp frontend). As well, zcomp frondend could call them in different context. One context(ie, zram init part) is it should be better to make sure successful allocation other context(ie, further stream allocation part for accelarating I/O speed) is just optional so let's pass gfp down from driver (ie, zcomp frontend) like normal MM convention. [sergey.senozhatsky@gmail.com: add missing __vmalloc zero and highmem gfps] Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-06-26zram: check comp algorithm availability earlierSergey Senozhatsky1-0/+1
Improvement idea by Marcin Jabrzyk. comp_algorithm_store() silently accepts any supplied algorithm name, because zram performs algorithm availability check later, during the device configuration phase in disksize_store() and emits the following error: "zram: Cannot initialise %s compressing backend" this error line is somewhat generic and, besides, can indicate a failed attempt to allocate compression backend's working buffers. add algorithm availability check to comp_algorithm_store(): echo lzz > /sys/block/zram0/comp_algorithm -bash: echo: write error: Invalid argument Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reported-by: Marcin Jabrzyk <m.jabrzyk@samsung.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08zram: propagate error to userMinchan Kim1-2/+2
When we initialized zcomp with single, we couldn't change max_comp_streams without zram reset but current interface doesn't show any error to user and even it changes max_comp_streams's value without any effect so it would make user very confusing. This patch prevents max_comp_streams's change when zcomp was initialized as single zcomp and emit the error to user(ex, echo). [akpm@linux-foundation.org: don't return with the lock held, per Sergey] [fengguang.wu@intel.com: fix coccinelle warnings] Signed-off-by: Minchan Kim <minchan@kernel.org> Cc: Nitin Gupta <ngupta@vflare.org> Cc: Jerome Marchand <jmarchan@redhat.com> Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08zram: make compression algorithm selection possibleSergey Senozhatsky1-0/+2
Add and document `comp_algorithm' device attribute. This attribute allows to show supported compression and currently selected compression algorithms: cat /sys/block/zram0/comp_algorithm [lzo] lz4 and change selected compression algorithm: echo lzo > /sys/block/zram0/comp_algorithm Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08zram: add set_max_streams knobSergey Senozhatsky1-0/+3
This patch allows to change max_comp_streams on initialised zcomp. Introduce zcomp set_max_streams() knob, zcomp_strm_multi_set_max_streams() and zcomp_strm_single_set_max_streams() callbacks to change streams limit for zcomp_strm_multi and zcomp_strm_single, accordingly. set_max_streams for single steam zcomp does nothing. If user has lowered the limit, then zcomp_strm_multi_set_max_streams() attempts to immediately free extra streams (as much as it can, depending on idle streams availability). Note, this patch does not allow to change stream 'policy' from single to multi stream (or vice versa) on already initialised compression backend. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08zram: add multi stream functionalitySergey Senozhatsky1-1/+3
Existing zram (zcomp) implementation has only one compression stream (buffer and algorithm private part), so in order to prevent data corruption only one write (compress operation) can use this compression stream, forcing all concurrent write operations to wait for stream lock to be released. This patch changes zcomp to keep a compression streams list of user-defined size (via sysfs device attr). Each write operation still exclusively holds compression stream, the difference is that we can have N write operations (depending on size of streams list) executing in parallel. See TEST section later in commit message for performance data. Introduce struct zcomp_strm_multi and a set of functions to manage zcomp_strm stream access. zcomp_strm_multi has a list of idle zcomp_strm structs, spinlock to protect idle list and wait queue, making it possible to perform parallel compressions. The following set of functions added: - zcomp_strm_multi_find()/zcomp_strm_multi_release() find and release a compression stream, implement required locking - zcomp_strm_multi_create()/zcomp_strm_multi_destroy() create and destroy zcomp_strm_multi zcomp ->strm_find() and ->strm_release() callbacks are set during initialisation to zcomp_strm_multi_find()/zcomp_strm_multi_release() correspondingly. Each time zcomp issues a zcomp_strm_multi_find() call, the following set of operations performed: - spin lock strm_lock - if idle list is not empty, remove zcomp_strm from idle list, spin unlock and return zcomp stream pointer to caller - if idle list is empty, current adds itself to wait queue. it will be awaken by zcomp_strm_multi_release() caller. zcomp_strm_multi_release(): - spin lock strm_lock - add zcomp stream to idle list - spin unlock, wake up sleeper Minchan Kim reported that spinlock-based locking scheme has demonstrated a severe perfomance regression for single compression stream case, comparing to mutex-based (see https://lkml.org/lkml/2014/2/18/16) base spinlock mutex ==Initial write ==Initial write ==Initial write records: 5 records: 5 records: 5 avg: 1642424.35 avg: 699610.40 avg: 1655583.71 std: 39890.95(2.43%) std: 232014.19(33.16%) std: 52293.96 max: 1690170.94 max: 1163473.45 max: 1697164.75 min: 1568669.52 min: 573429.88 min: 1553410.23 ==Rewrite ==Rewrite ==Rewrite records: 5 records: 5 records: 5 avg: 1611775.39 avg: 501406.64 avg: 1684419.11 std: 17144.58(1.06%) std: 15354.41(3.06%) std: 18367.42 max: 1641800.95 max: 531356.78 max: 1706445.84 min: 1593515.27 min: 488817.78 min: 1655335.73 When only one compression stream available, mutex with spin on owner tends to perform much better than frequent wait_event()/wake_up(). This is why single stream implemented as a special case with mutex locking. Introduce and document zram device attribute max_comp_streams. This attr shows and stores current zcomp's max number of zcomp streams (max_strm). Extend zcomp's zcomp_create() with `max_strm' parameter. `max_strm' limits the number of zcomp_strm structs in compression backend's idle list (max_comp_streams). max_comp_streams used during initialisation as follows: -- passing to zcomp_create() max_strm equals to 1 will initialise zcomp using single compression stream zcomp_strm_single (mutex-based locking). -- passing to zcomp_create() max_strm greater than 1 will initialise zcomp using multi compression stream zcomp_strm_multi (spinlock-based locking). default max_comp_streams value is 1, meaning that zram with single stream will be initialised. Later patch will introduce configuration knob to change max_comp_streams on already initialised and used zcomp. TEST iozone -t 3 -R -r 16K -s 60M -I +Z test base 1 strm (mutex) 3 strm (spinlock) ----------------------------------------------------------------------- Initial write 589286.78 583518.39 718011.05 Rewrite 604837.97 596776.38 1515125.72 Random write 584120.11 595714.58 1388850.25 Pwrite 535731.17 541117.38 739295.27 Fwrite 1418083.88 1478612.72 1484927.06 Usage example: set max_comp_streams to 4 echo 4 > /sys/block/zram0/max_comp_streams show current max_comp_streams (default value is 1). cat /sys/block/zram0/max_comp_streams Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08zram: factor out single stream compressionSergey Senozhatsky1-2/+5
This is preparation patch to add multi stream support to zcomp. Introduce struct zcomp_strm_single and a set of functions to manage zcomp_strm stream access. zcomp_strm_single implements single compession stream, same way as current zcomp implementation. This moves zcomp_strm stream control and locking from zcomp, so compressing backend zcomp is not aware of required locking. Single and multi streams require different locking schemes. Minchan Kim reported that spinlock-based locking scheme (which is used in multi stream implementation) has demonstrated a severe perfomance regression for single compression stream case, comparing to mutex-based. see https://lkml.org/lkml/2014/2/18/16 The following set of functions added: - zcomp_strm_single_find()/zcomp_strm_single_release() find and release a compression stream, implement required locking - zcomp_strm_single_create()/zcomp_strm_single_destroy() create and destroy zcomp_strm_single New ->strm_find() and ->strm_release() callbacks added to zcomp, which are set to zcomp_strm_single_find() and zcomp_strm_single_release() during initialisation. Instead of direct locking and zcomp_strm access from zcomp_strm_find() and zcomp_strm_release(), zcomp now calls ->strm_find() and ->strm_release() correspondingly. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-08zram: introduce compressing backend abstractionSergey Senozhatsky1-0/+58
ZRAM performs direct LZO compression algorithm calls, making it the one and only option. While LZO is generally performs well, LZ4 algorithm tends to have a faster decompression (see http://code.google.com/p/lz4/ for full report) Name Ratio C.speed D.speed MB/s MB/s LZ4 (r101) 2.084 422 1820 LZO 2.06 2.106 414 600 Thus, users who have mostly read (decompress) usage scenarious or mixed workflow (writes with relatively high read ops number) will benefit from using LZ4 compression backend. Introduce compressing backend abstraction zcomp in order to support multiple compression algorithms with the following set of operations: .create .destroy .compress .decompress Schematically zram write() usually contains the following steps: 0) preparation (decompression of partioal IO, etc.) 1) lock buffer_lock mutex (protects meta compress buffers) 2) compress (using meta compress buffers) 3) alloc and map zs_pool object 4) copy compressed data (from meta compress buffers) to object allocated by 3) 5) free previous pool page, assign a new one 6) unlock buffer_lock mutex As we can see, compressing buffers must remain untouched from 1) to 4), because, otherwise, concurrent write() can overwrite data. At the same time, zram_meta must be aware of a) specific compression algorithm memory requirements and b) necessary locking to protect compression buffers. To remove requirement a) new struct zcomp_strm introduced, which contains a compress/decompress `buffer' and compression algorithm `private' part. While struct zcomp implements zcomp_strm stream handling and locking and removes requirement b) from zram meta. zcomp ->create() and ->destroy(), respectively, allocate and deallocate algorithm specific zcomp_strm `private' part. Every zcomp has zcomp stream and mutex to protect its compression stream. Stream usage semantics remains the same -- only one write can hold stream lock and use its buffers. zcomp_strm_find() turns caller into exclusive user of a stream (holding stream mutex until zram release stream), and zcomp_strm_release() makes zcomp stream available (unlock the stream mutex). Hence no concurrent write (compression) operations possible at the moment. iozone -t 3 -R -r 16K -s 60M -I +Z test base patched -------------------------------------------------- Initial write 597992.91 591660.58 Rewrite 609674.34 616054.97 Read 2404771.75 2452909.12 Re-read 2459216.81 2470074.44 Reverse Read 1652769.66 1589128.66 Stride read 2202441.81 2202173.31 Random read 2236311.47 2276565.31 Mixed workload 1423760.41 1709760.06 Random write 579584.08 615933.86 Pwrite 597550.02 594933.70 Pread 1703672.53 1718126.72 Fwrite 1330497.06 1461054.00 Fread 3922851.00 3957242.62 Usage examples: comp = zcomp_create(NAME) /* NAME e.g. "lzo" */ which initialises compressing backend if requested algorithm is supported. Compress: zstrm = zcomp_strm_find(comp) zcomp_compress(comp, zstrm, src, &dst_len) [..] /* copy compressed data */ zcomp_strm_release(comp, zstrm) Decompress: zcomp_decompress(comp, src, src_len, dst); Free compessing backend and its zcomp stream: zcomp_destroy(comp) Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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