The patch titled mm: export account_page_dirty() has been added to the -mm tree. Its filename is mm-export-account_page_dirty.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: mm: export account_page_dirty() From: Michael Rubin <mrubin@xxxxxxxxxx> To help developers and applications gain visibility into writeback behaviour this patch adds two counters to /proc/vmstat. # grep nr_dirtied /proc/vmstat nr_dirtied 3747 # grep nr_written /proc/vmstat nr_written 3618 These entries allow user apps to understand writeback behaviour over time and learn how it is impacting their performance. Currently there is no way to inspect dirty and writeback speed over time. It's not possible for nr_dirty/nr_writeback. These entries are necessary to give visibility into writeback behaviour. We have /proc/diskstats which lets us understand the io in the block layer. We have blktrace for more in depth understanding. We have e2fsprogs and debugsfs to give insight into the file systems behaviour, but we don't offer our users the ability understand what writeback is doing. There is no way to know how active it is over the whole system, if it's falling behind or to quantify it's efforts. With these values exported users can easily see how much data applications are sending through writeback and also at what rates writeback is processing this data. Comparing the rates of change between the two allow developers to see when writeback is not able to keep up with incoming traffic and the rate of dirty memory being sent to the IO back end. This allows folks to understand their io workloads and track kernel issues. Non kernel engineers at Google often use these counters to solve puzzling performance problems. Patch #4 adds a pernode vmstat file with nr_dirtied and nr_written Patch #5 add writeback thresholds to /proc/vmstat Currently these values are in debugfs. But they should be promoted to /proc since they are useful for developers who are writing databases and file servers and are not debugging the kernel. The output is as below: # grep threshold /proc/vmstat nr_pages_dirty_threshold 409111 nr_pages_dirty_background_threshold 818223 This patch: Export account_page_dirty(). This allows code outside of the mm core to safely manipulate page state and not worry about the other accounting. Not using these routines means that some code will lose track of the accounting and we get bugs. This has happened once already. Signed-off-by: Michael Rubin <mrubin@xxxxxxxxxx> Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Nick Piggin <nickpiggin@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page-writeback.c | 1 + 1 file changed, 1 insertion(+) diff -puN mm/page-writeback.c~mm-export-account_page_dirty mm/page-writeback.c --- a/mm/page-writeback.c~mm-export-account_page_dirty +++ a/mm/page-writeback.c @@ -682,6 +682,7 @@ void throttle_vm_writeout(gfp_t gfp_mask break; } } +EXPORT_SYMBOL(account_page_dirtied); /* * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs _ Patches currently in -mm which might be from mrubin@xxxxxxxxxx are vmscan-do-not-writeback-filesystem-pages-in-direct-reclaim.patch vmscan-kick-flusher-threads-to-clean-pages-when-reclaim-is-encountering-dirty-pages.patch mm-export-account_page_dirty.patch mm-add-account_page_writeback.patch writeback-add-nr_dirtied-and-nr_written-to-proc-vmstat.patch writeback-add-nr_dirtied-and-nr_written-to-proc-vmstat-fix.patch writeback-add-sys-devices-system-node-node-vmstat.patch writeback-report-dirty-thresholds-in-proc-vmstat.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html