kernel/linux.git/drivers/md/raid5.h, branch v5.15.7

md/raid5: let multiple devices of stripe_head share page

2020-09-24T23:44:44+00:00

In current implementation, grow_buffers() uses alloc_page() to allocate the buffers for each stripe_head, i.e. allocate a page for each dev[i] in stripe_head. After setting stripe_size as a configurable value by writing sysfs entry, it means that we always allocate 64K buffers, but just use 4K of them when stripe_size is 4K in 64KB arm64. To avoid wasting memory, we try to let multiple sh->dev share one real page. That means, multiple sh->dev[i].page will point to the only page with different offset. Example of 64K PAGE_SIZE and 4K stripe_size as following: 64K PAGE_SIZE +---+---+---+---+------------------------------+ | | | | | | | | | | +-+-+-+-+-+-+-+-+------------------------------+ ^ ^ ^ ^ | | | +----------------------------+ | | | | | | +-------------------+ | | | | | | +----------+ | | | | | | +-+ | | | | | | | +-----+-----+------+-----+------+-----+------+------+ sh | offset(0) | offset(4K) | offset(8K) | offset(12K) | + +-----------+------------+------------+-------------+ +----> dev[0].page dev[1].page dev[2].page dev[3].page A new 'pages' array will be added into stripe_head to record shared page used by this stripe_head. Allocate them when grow_buffers() and free them when shrink_buffers(). After trying to share page, the users of sh->dev[i].page need to take care of the related page offset: page of issued bio and page passed to xor compution functions. But thanks for previous different page offset supported. Here, we just need to set correct dev[i].offset. Signed-off-by: Yufen Yu Signed-off-by: Song Liu

md/raid5: add a new member of offset into r5dev

2020-09-24T23:44:44+00:00

Add a new member of offset into struct r5dev. It indicates the offset of related dev[i].page. For now, since each device have a privated page, the value is always 0. Thus, we set offset as 0 when allcate page in grow_buffers() and resize_stripes(). To support following different page offset, we try to use the page offset rather than '0' directly for async_memcpy() and ops_run_io(). We try to support different page offset for xor compution functions in the following. To avoid repeatly allocate a new array each time, we add a memory region into scribble buffer to record offset. No functional change. Signed-off-by: Yufen Yu Signed-off-by: Song Liu

Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-08-11T02:07:44+00:00

Pull locking updates from Thomas Gleixner: "A set of locking fixes and updates: - Untangle the header spaghetti which causes build failures in various situations caused by the lockdep additions to seqcount to validate that the write side critical sections are non-preemptible. - The seqcount associated lock debug addons which were blocked by the above fallout. seqcount writers contrary to seqlock writers must be externally serialized, which usually happens via locking - except for strict per CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot validate that the lock is held. This new debug mechanism adds the concept of associated locks. sequence count has now lock type variants and corresponding initializers which take a pointer to the associated lock used for writer serialization. If lockdep is enabled the pointer is stored and write_seqcount_begin() has a lockdep assertion to validate that the lock is held. Aside of the type and the initializer no other code changes are required at the seqcount usage sites. The rest of the seqcount API is unchanged and determines the type at compile time with the help of _Generic which is possible now that the minimal GCC version has been moved up. Adding this lockdep coverage unearthed a handful of seqcount bugs which have been addressed already independent of this. While generally useful this comes with a Trojan Horse twist: On RT kernels the write side critical section can become preemtible if the writers are serialized by an associated lock, which leads to the well known reader preempts writer livelock. RT prevents this by storing the associated lock pointer independent of lockdep in the seqcount and changing the reader side to block on the lock when a reader detects that a writer is in the write side critical section. - Conversion of seqcount usage sites to associated types and initializers" * tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits) locking/seqlock, headers: Untangle the spaghetti monster locking, arch/ia64: Reduce header dependencies by moving XTP bits into the new header x86/headers: Remove APIC headers from seqcount: More consistent seqprop names seqcount: Compress SEQCNT_LOCKNAME_ZERO() seqlock: Fold seqcount_LOCKNAME_init() definition seqlock: Fold seqcount_LOCKNAME_t definition seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g hrtimer: Use sequence counter with associated raw spinlock kvm/eventfd: Use sequence counter with associated spinlock userfaultfd: Use sequence counter with associated spinlock NFSv4: Use sequence counter with associated spinlock iocost: Use sequence counter with associated spinlock raid5: Use sequence counter with associated spinlock vfs: Use sequence counter with associated spinlock timekeeping: Use sequence counter with associated raw spinlock xfrm: policy: Use sequence counters with associated lock netfilter: nft_set_rbtree: Use sequence counter with associated rwlock netfilter: conntrack: Use sequence counter with associated spinlock sched: tasks: Use sequence counter with associated spinlock ...

raid5: Use sequence counter with associated spinlock

2020-07-29T14:14:27+00:00

A sequence counter write side critical section must be protected by some form of locking to serialize writers. A plain seqcount_t does not contain the information of which lock must be held when entering a write side critical section. Use the new seqcount_spinlock_t data type, which allows to associate a spinlock with the sequence counter. This enables lockdep to verify that the spinlock used for writer serialization is held when the write side critical section is entered. If lockdep is disabled this lock association is compiled out and has neither storage size nor runtime overhead. Signed-off-by: Ahmed S. Darwish Signed-off-by: Peter Zijlstra (Intel) Acked-by: Song Liu Link: https://lkml.kernel.org/r/20200720155530.1173732-20-a.darwish@linutronix.de

md/raid5: set default stripe_size as 4096

2020-07-22T00:18:17+00:00

In RAID5, if issued bio size is bigger than stripe_size, it will be split in the unit of stripe_size and process them one by one. Even for size less then stripe_size, RAID5 also request data from disk at least of stripe_size. Nowdays, stripe_size is equal to the value of PAGE_SIZE. Since filesystem usually issue bio in the unit of 4KB, there is no problem for PAGE_SIZE as 4KB. But, for 64KB PAGE_SIZE, bio from filesystem requests 4KB data while RAID5 issue IO at least stripe_size (64KB) each time. That will waste resource of disk bandwidth and compute xor. To avoding the waste, we want to make stripe_size configurable. This patch just set default stripe_size as 4096. User can also set the value bigger than 4KB for some special requirements, such as we know the issued io size is more than 4KB. To evaluate the new feature, we create raid5 device '/dev/md5' with 4 SSD disk and test it on arm64 machine with 64KB PAGE_SIZE. 1) We format /dev/md5 with mkfs.ext4 and mount ext4 with default configure on /mnt directory. Then, trying to test it by dbench with command: dbench -D /mnt -t 1000 10. Result show as: 'stripe_size = 64KB' Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 9805011 0.021 64.728 Close 7202525 0.001 0.120 Rename 415213 0.051 44.681 Unlink 1980066 0.079 93.147 Deltree 240 1.793 6.516 Mkdir 120 0.004 0.007 Qpathinfo 8887512 0.007 37.114 Qfileinfo 1557262 0.001 0.030 Qfsinfo 1629582 0.012 0.152 Sfileinfo 798756 0.040 57.641 Find 3436004 0.019 57.782 WriteX 4887239 0.021 57.638 ReadX 15370483 0.005 37.818 LockX 31934 0.003 0.022 UnlockX 31933 0.001 0.021 Flush 687205 13.302 530.088 Throughput 307.799 MB/sec 10 clients 10 procs max_latency=530.091 ms ------------------------------------------------------- 'stripe_size = 4KB' Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 11999166 0.021 36.380 Close 8814128 0.001 0.122 Rename 508113 0.051 29.169 Unlink 2423242 0.070 38.141 Deltree 300 1.885 7.155 Mkdir 150 0.004 0.006 Qpathinfo 10875921 0.007 35.485 Qfileinfo 1905837 0.001 0.032 Qfsinfo 1994304 0.012 0.125 Sfileinfo 977450 0.029 26.489 Find 4204952 0.019 9.361 WriteX 5981890 0.019 27.804 ReadX 18809742 0.004 33.491 LockX 39074 0.003 0.025 UnlockX 39074 0.001 0.014 Flush 841022 10.712 458.848 Throughput 376.777 MB/sec 10 clients 10 procs max_latency=458.852 ms ------------------------------------------------------- It show that setting stripe_size as 4KB has higher thoughput, i.e. (376.777 vs 307.799) and has smaller latency than that setting as 64KB. 2) We try to evaluate IO throughput for /dev/md5 by fio with config: [4KB randwrite] direct=1 numjob=2 iodepth=64 ioengine=libaio filename=/dev/md5 bs=4KB rw=randwrite [64KB write] direct=1 numjob=2 iodepth=64 ioengine=libaio filename=/dev/md5 bs=1MB rw=write The result as follow: + + | stripe_size(64KB) | stripe_size(4KB) +----------------------------------------------------+ 4KB randwrite | 15MB/s | 100MB/s +----------------------------------------------------+ 1MB write | 1000MB/s | 700MB/s The result show that when size of io is bigger than 4KB (64KB), 64KB stripe_size has much higher IOPS. But for 4KB randwrite, that means, size of io issued to device are smaller, 4KB stripe_size have better performance. Normally, default value (4096) can get relatively good performance. But if each issued io is bigger than 4096, setting value more than 4096 may get better performance. Here, we just set default stripe_size as 4096, and we will try to support setting different stripe_size by sysfs interface in the following patch. Signed-off-by: Yufen Yu Signed-off-by: Song Liu

md/raid456: convert macro STRIPE_* to RAID5_STRIPE_*

2020-07-22T00:18:12+00:00

Convert macro STRIPE_SIZE, STRIPE_SECTORS and STRIPE_SHIFT to RAID5_STRIPE_SIZE(), RAID5_STRIPE_SECTORS() and RAID5_STRIPE_SHIFT(). This patch is prepare for the following adjustable stripe_size. It will not change any existing functionality. Signed-off-by: Yufen Yu Signed-off-by: Song Liu

raid5: use bio_end_sector in r5_next_bio

2019-09-13T20:14:43+00:00

Actually, we calculate bio's end sector here, so use the common way for the purpose. Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu

raid5: remove STRIPE_OPS_REQ_PENDING

2019-09-13T20:14:39+00:00

This stripe state is not used anymore after commit 51acbcec6c42b24 ("md: remove CONFIG_MULTICORE_RAID456"), so remove the obsoleted state. gjiang@nb01257:~/md$ grep STRIPE_OPS_REQ_PENDING drivers/md/ -r drivers/md/raid5.c: (1 << STRIPE_OPS_REQ_PENDING) | drivers/md/raid5.h: STRIPE_OPS_REQ_PENDING, Signed-off-by: Guoqing Jiang Signed-off-by: Song Liu

md: convert to kvmalloc

2019-03-12T17:04:02+00:00

The code really just wants a big flat buffer, so just do that. Link: http://lkml.kernel.org/r/20181217131929.11727-3-kent.overstreet@gmail.com Signed-off-by: Kent Overstreet Reviewed-by: Matthew Wilcox Cc: Shaohua Li Cc: Alexey Dobriyan Cc: Al Viro Cc: Dave Hansen Cc: Eric Paris Cc: Marcelo Ricardo Leitner Cc: Neil Horman Cc: Paul Moore Cc: Pravin B Shelar Cc: Stephen Smalley Cc: Vlad Yasevich Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md

2018-06-09T19:01:36+00:00

Pull MD updates from Shaohua Li: "A few fixes of MD for this merge window. Mostly bug fixes: - raid5 stripe batch fix from Amy - Read error handling for raid1 FailFast device from Gioh - raid10 recovery NULL pointer dereference fix from Guoqing - Support write hint for raid5 stripe cache from Mariusz - Fixes for device hot add/remove from Neil and Yufen - Improve flush bio scalability from Xiao" * 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md: MD: fix lock contention for flush bios md/raid5: Assigning NULL to sh->batch_head before testing bit R5_Overlap of a stripe md/raid1: add error handling of read error from FailFast device md: fix NULL dereference of mddev->pers in remove_and_add_spares() raid5: copy write hint from origin bio to stripe md: fix two problems with setting the "re-add" device state. raid10: check bio in r10buf_pool_free to void NULL pointer dereference md: fix an error code format and remove unsed bio_sector