The patch titled writeback: add trace event for balance_dirty_pages() has been added to the -mm tree. Its filename is writeback-add-trace-event-for-balance_dirty_pages.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: writeback: add trace event for balance_dirty_pages() From: Wu Fengguang <fengguang.wu@xxxxxxxxx> Here is an interesting test to verify the theory with balance_dirty_pages() tracing. On a partition that can do ~60MB/s, a sparse file is created and 4 rsync tasks with different write bandwidth started: dd if=/dev/zero of=/mnt/1T bs=1M count=1 seek=1024000 echo 1 > /debug/tracing/events/writeback/balance_dirty_pages/enable rsync localhost:/mnt/1T /mnt/a --bwlimit 10000& rsync localhost:/mnt/1T /mnt/A --bwlimit 10000& rsync localhost:/mnt/1T /mnt/b --bwlimit 20000& rsync localhost:/mnt/1T /mnt/c --bwlimit 30000& Trace outputs within 0.1 second, grouped by tasks: rsync-3824 [004] 15002.076447: balance_dirty_pages: bdi=btrfs-2 weight=15% limit=130876 gap=5340 dirtied=192 pause=20 rsync-3822 [003] 15002.091701: balance_dirty_pages: bdi=btrfs-2 weight=15% limit=130777 gap=5113 dirtied=192 pause=20 rsync-3821 [006] 15002.004667: balance_dirty_pages: bdi=btrfs-2 weight=30% limit=129570 gap=3714 dirtied=64 pause=8 rsync-3821 [006] 15002.012654: balance_dirty_pages: bdi=btrfs-2 weight=30% limit=129589 gap=3733 dirtied=64 pause=8 rsync-3821 [006] 15002.021838: balance_dirty_pages: bdi=btrfs-2 weight=30% limit=129604 gap=3748 dirtied=64 pause=8 rsync-3821 [004] 15002.091193: balance_dirty_pages: bdi=btrfs-2 weight=29% limit=129583 gap=3983 dirtied=64 pause=8 rsync-3821 [004] 15002.102729: balance_dirty_pages: bdi=btrfs-2 weight=29% limit=129594 gap=3802 dirtied=64 pause=8 rsync-3821 [000] 15002.109252: balance_dirty_pages: bdi=btrfs-2 weight=29% limit=129619 gap=3827 dirtied=64 pause=8 rsync-3823 [002] 15002.009029: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128762 gap=2842 dirtied=64 pause=12 rsync-3823 [002] 15002.021598: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128813 gap=3021 dirtied=64 pause=12 rsync-3823 [003] 15002.032973: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128805 gap=2885 dirtied=64 pause=12 rsync-3823 [003] 15002.048800: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128823 gap=2967 dirtied=64 pause=12 rsync-3823 [003] 15002.060728: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128821 gap=3221 dirtied=64 pause=12 rsync-3823 [000] 15002.073152: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128825 gap=3225 dirtied=64 pause=12 rsync-3823 [005] 15002.090111: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128782 gap=3214 dirtied=64 pause=12 rsync-3823 [004] 15002.102520: balance_dirty_pages: bdi=btrfs-2 weight=39% limit=128764 gap=3036 dirtied=64 pause=12 The data vividly show that - the heaviest writer is throttled a bit (weight=39%) - the lighter writers run at full speed (weight=15%,15%,30%) rsync is smart enough to compensate for the in-kernel pause time Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> Cc: Chris Mason <chris.mason@xxxxxxxxxx> Cc: Dave Chinner <david@xxxxxxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Jan Kara <jack@xxxxxxx> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Cc: Li Shaohua <shaohua.li@xxxxxxxxx> Cc: Theodore Ts'o <tytso@xxxxxxx> Cc: Richard Kennedy <richard@xxxxxxxxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Mel Gorman <mel@xxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Michael Rubin <mrubin@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/trace/events/writeback.h | 61 +++++++++++++++++++++++++++-- mm/page-writeback.c | 6 ++ 2 files changed, 64 insertions(+), 3 deletions(-) diff -puN include/trace/events/writeback.h~writeback-add-trace-event-for-balance_dirty_pages include/trace/events/writeback.h --- a/include/trace/events/writeback.h~writeback-add-trace-event-for-balance_dirty_pages +++ a/include/trace/events/writeback.h @@ -147,11 +147,66 @@ DEFINE_EVENT(wbc_class, name, \ DEFINE_WBC_EVENT(wbc_writeback_start); DEFINE_WBC_EVENT(wbc_writeback_written); DEFINE_WBC_EVENT(wbc_writeback_wait); -DEFINE_WBC_EVENT(wbc_balance_dirty_start); -DEFINE_WBC_EVENT(wbc_balance_dirty_written); -DEFINE_WBC_EVENT(wbc_balance_dirty_wait); DEFINE_WBC_EVENT(wbc_writepage); +#define BDP_PERCENT(a, b, c) ((__entry->a - __entry->b) * 100 * c + \ + __entry->bdi_limit/2) / (__entry->bdi_limit|1) +TRACE_EVENT(balance_dirty_pages, + + TP_PROTO(struct backing_dev_info *bdi, + long bdi_dirty, + long bdi_limit, + long task_limit, + long pages_dirtied, + long pause), + + TP_ARGS(bdi, bdi_dirty, bdi_limit, task_limit, + pages_dirtied, pause), + + TP_STRUCT__entry( + __array(char, bdi, 32) + __field(long, bdi_dirty) + __field(long, bdi_limit) + __field(long, task_limit) + __field(long, pages_dirtied) + __field(long, pause) + ), + + TP_fast_assign( + strlcpy(__entry->bdi, dev_name(bdi->dev), 32); + __entry->bdi_dirty = bdi_dirty; + __entry->bdi_limit = bdi_limit; + __entry->task_limit = task_limit; + __entry->pages_dirtied = pages_dirtied; + __entry->pause = pause * 1000 / HZ; + ), + + + /* + * [..................soft throttling range.........] + * ^ |<=========== bdi_gap =========>| + * background_thresh |<== task_gap ==>| + * -------------------|-------+----------------|--------------| + * (bdi_limit * 7/8)^ ^bdi_dirty ^task_limit ^bdi_limit + * + * Reasonable large gaps help produce smooth pause times. + */ + TP_printk("bdi=%s bdi_dirty=%lu bdi_limit=%lu task_limit=%lu " + "task_weight=%ld%% task_gap=%ld%% bdi_gap=%ld%% " + "pages_dirtied=%lu pause=%lu", + __entry->bdi, + __entry->bdi_dirty, + __entry->bdi_limit, + __entry->task_limit, + /* task weight: proportion of recent dirtied pages */ + BDP_PERCENT(bdi_limit, task_limit, TASK_SOFT_DIRTY_LIMIT), + BDP_PERCENT(task_limit, bdi_dirty, TASK_SOFT_DIRTY_LIMIT), + BDP_PERCENT(bdi_limit, bdi_dirty, BDI_SOFT_DIRTY_LIMIT), + __entry->pages_dirtied, + __entry->pause + ) +); + DECLARE_EVENT_CLASS(writeback_congest_waited_template, TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed), diff -puN mm/page-writeback.c~writeback-add-trace-event-for-balance_dirty_pages mm/page-writeback.c --- a/mm/page-writeback.c~writeback-add-trace-event-for-balance_dirty_pages +++ a/mm/page-writeback.c @@ -629,6 +629,12 @@ static void balance_dirty_pages(struct a pause = clamp_val(pause, 1, HZ/10); pause: + trace_balance_dirty_pages(bdi, + bdi_dirty, + bdi_thresh, + task_thresh, + pages_dirtied, + pause); bdi_update_write_bandwidth(bdi, &bw_time, &bw_written); __set_current_state(TASK_INTERRUPTIBLE); io_schedule_timeout(pause); _ Patches currently in -mm which might be from fengguang.wu@xxxxxxxxx are linux-next.patch writeback-integrated-background-writeback-work.patch writeback-trace-wakeup-event-for-background-writeback.patch writeback-stop-background-kupdate-works-from-livelocking-other-works.patch writeback-stop-background-kupdate-works-from-livelocking-other-works-update.patch writeback-avoid-livelocking-wb_sync_all-writeback.patch writeback-avoid-livelocking-wb_sync_all-writeback-update.patch writeback-check-skipped-pages-on-wb_sync_all.patch writeback-check-skipped-pages-on-wb_sync_all-update.patch writeback-check-skipped-pages-on-wb_sync_all-update-fix.patch writeback-io-less-balance_dirty_pages.patch writeback-consolidate-variable-names-in-balance_dirty_pages.patch writeback-per-task-rate-limit-on-balance_dirty_pages.patch writeback-per-task-rate-limit-on-balance_dirty_pages-fix.patch writeback-prevent-duplicate-balance_dirty_pages_ratelimited-calls.patch writeback-account-per-bdi-accumulated-written-pages.patch writeback-bdi-write-bandwidth-estimation.patch writeback-show-bdi-write-bandwidth-in-debugfs.patch writeback-quit-throttling-when-bdi-dirty-pages-dropped-low.patch writeback-reduce-per-bdi-dirty-threshold-ramp-up-time.patch writeback-make-reasonable-gap-between-the-dirty-background-thresholds.patch writeback-scale-down-max-throttle-bandwidth-on-concurrent-dirtiers.patch writeback-add-trace-event-for-balance_dirty_pages.patch writeback-make-nr_to_write-a-per-file-limit.patch mm-page-writebackc-fix-__set_page_dirty_no_writeback-return-value.patch mm-find_get_pages_contig-fixlet.patch mm-smaps-export-mlock-information.patch memcg-add-page_cgroup-flags-for-dirty-page-tracking.patch memcg-document-cgroup-dirty-memory-interfaces.patch memcg-document-cgroup-dirty-memory-interfaces-fix.patch memcg-create-extensible-page-stat-update-routines.patch memcg-add-lock-to-synchronize-page-accounting-and-migration.patch writeback-create-dirty_info-structure.patch memcg-add-dirty-page-accounting-infrastructure.patch memcg-add-kernel-calls-for-memcg-dirty-page-stats.patch memcg-add-dirty-limits-to-mem_cgroup.patch memcg-add-dirty-limits-to-mem_cgroup-use-native-word-to-represent-dirtyable-pages.patch memcg-add-dirty-limits-to-mem_cgroup-catch-negative-per-cpu-sums-in-dirty-info.patch memcg-add-dirty-limits-to-mem_cgroup-avoid-overflow-in-memcg_hierarchical_free_pages.patch memcg-add-dirty-limits-to-mem_cgroup-correct-memcg_hierarchical_free_pages-return-type.patch memcg-add-dirty-limits-to-mem_cgroup-avoid-free-overflow-in-memcg_hierarchical_free_pages.patch memcg-cpu-hotplug-lockdep-warning-fix.patch memcg-add-cgroupfs-interface-to-memcg-dirty-limits.patch memcg-break-out-event-counters-from-other-stats.patch memcg-check-memcg-dirty-limits-in-page-writeback.patch memcg-use-native-word-page-statistics-counters.patch memcg-use-native-word-page-statistics-counters-fix.patch memcg-add-mem_cgroup-parameter-to-mem_cgroup_page_stat.patch memcg-pass-mem_cgroup-to-mem_cgroup_dirty_info.patch memcg-make-throttle_vm_writeout-memcg-aware.patch memcg-make-throttle_vm_writeout-memcg-aware-fix.patch memcg-simplify-mem_cgroup_page_stat.patch memcg-simplify-mem_cgroup_dirty_info.patch memcg-make-mem_cgroup_page_stat-return-value-unsigned.patch memcg-use-zalloc-rather-than-mallocmemset.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