summaryrefslogtreecommitdiff
path: root/drivers/block/zram/Kconfig
diff options
context:
space:
mode:
authorMinchan Kim <minchan@kernel.org>2018-06-08 03:05:49 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-08 03:34:34 +0300
commitc0265342bff4fcaa2cdf13f4596244c18d4a7ae5 (patch)
tree51ce5d5c93d5931d7f2ce28e2da4509bba234b25 /drivers/block/zram/Kconfig
parentd7eac6b6e1838ef1a1400df4ec55daa34bbc855e (diff)
downloadlinux-c0265342bff4fcaa2cdf13f4596244c18d4a7ae5.tar.xz
zram: introduce zram memory tracking
zRam as swap is useful for small memory device. However, swap means those pages on zram are mostly cold pages due to VM's LRU algorithm. Especially, once init data for application are touched for launching, they tend to be not accessed any more and finally swapped out. zRAM can store such cold pages as compressed form but it's pointless to keep in memory. Better idea is app developers free them directly rather than remaining them on heap. This patch tell us last access time of each block of zram via "cat /sys/kernel/debug/zram/zram0/block_state". The output is as follows, 300 75.033841 .wh 301 63.806904 s.. 302 63.806919 ..h First column is zram's block index and 3rh one represents symbol (s: same page w: written page to backing store h: huge page) of the block state. Second column represents usec time unit of the block was last accessed. So above example means the 300th block is accessed at 75.033851 second and it was huge so it was written to the backing store. Admin can leverage this information to catch cold|incompressible pages of process with *pagemap* once part of heaps are swapped out. I used the feature a few years ago to find memory hoggers in userspace to notify them what memory they have wasted without touch for a long time. With it, they could reduce unnecessary memory space. However, at that time, I hacked up zram for the feature but now I need the feature again so I decided it would be better to upstream rather than keeping it alone. I hope I submit the userspace tool to use the feature soon. [akpm@linux-foundation.org: fix i386 printk warning] [minchan@kernel.org: use ktime_get_boottime() instead of sched_clock()] Link: http://lkml.kernel.org/r/20180420063525.GA253739@rodete-desktop-imager.corp.google.com [akpm@linux-foundation.org: documentation tweak] [akpm@linux-foundation.org: fix i386 printk warning] [minchan@kernel.org: fix compile warning] Link: http://lkml.kernel.org/r/20180508104849.GA8209@rodete-desktop-imager.corp.google.com [rdunlap@infradead.org: fix printk formats] Link: http://lkml.kernel.org/r/3652ccb1-96ef-0b0b-05d1-f661d7733dcc@infradead.org Link: http://lkml.kernel.org/r/20180416090946.63057-5-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/block/zram/Kconfig')
-rw-r--r--drivers/block/zram/Kconfig14
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
index ac3a31d433b2..635235759a0a 100644
--- a/drivers/block/zram/Kconfig
+++ b/drivers/block/zram/Kconfig
@@ -13,7 +13,7 @@ config ZRAM
It has several use cases, for example: /tmp storage, use as swap
disks and maybe many more.
- See zram.txt for more information.
+ See Documentation/blockdev/zram.txt for more information.
config ZRAM_WRITEBACK
bool "Write back incompressible page to backing device"
@@ -25,4 +25,14 @@ config ZRAM_WRITEBACK
For this feature, admin should set up backing device via
/sys/block/zramX/backing_dev.
- See zram.txt for more infomration.
+ See Documentation/blockdev/zram.txt for more information.
+
+config ZRAM_MEMORY_TRACKING
+ bool "Track zRam block status"
+ depends on ZRAM && DEBUG_FS
+ help
+ With this feature, admin can track the state of allocated blocks
+ of zRAM. Admin could see the information via
+ /sys/kernel/debug/zram/zramX/block_state.
+
+ See Documentation/blockdev/zram.txt for more information.