From: Wu Fengguang <fengguang.wu@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>, Wu Fengguang <fengguang.wu@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: linux-mm <linux-mm@kvack.org>
Cc: <linux-fsdevel@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 14/47] writeback: add trace event for balance_dirty_pages()
Date: Mon, 13 Dec 2010 14:43:03 +0800 [thread overview]
Message-ID: <20101213064838.654882390@intel.com> (raw)
In-Reply-To: 20101213064249.648862451@intel.com
[-- Attachment #1: writeback-trace-balance_dirty_pages.patch --]
[-- Type: text/plain, Size: 5875 bytes --]
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@intel.com>
---
include/trace/events/writeback.h | 61 +++++++++++++++++++++++++++--
mm/page-writeback.c | 6 ++
2 files changed, 64 insertions(+), 3 deletions(-)
--- linux-next.orig/include/trace/events/writeback.h 2010-12-08 22:44:20.000000000 +0800
+++ linux-next/include/trace/events/writeback.h 2010-12-08 22:44:26.000000000 +0800
@@ -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+dirty)/2 |<== 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),
--- linux-next.orig/mm/page-writeback.c 2010-12-08 22:44:26.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-12-08 22:44:26.000000000 +0800
@@ -666,6 +666,12 @@ 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);
next prev parent reply other threads:[~2010-12-13 6:43 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-13 6:42 [PATCH 00/47] IO-less dirty throttling v3 Wu Fengguang
2010-12-13 6:42 ` [PATCH 01/47] writeback: enabling gate limit for light dirtied bdi Wu Fengguang
2010-12-13 6:42 ` [PATCH 02/47] writeback: safety margin for bdi stat error Wu Fengguang
2010-12-13 6:42 ` [PATCH 03/47] writeback: IO-less balance_dirty_pages() Wu Fengguang
2010-12-13 6:42 ` [PATCH 04/47] writeback: consolidate variable names in balance_dirty_pages() Wu Fengguang
2010-12-13 6:42 ` [PATCH 05/47] writeback: per-task rate limit on balance_dirty_pages() Wu Fengguang
2010-12-13 6:42 ` [PATCH 06/47] writeback: prevent duplicate balance_dirty_pages_ratelimited() calls Wu Fengguang
2010-12-13 6:42 ` [PATCH 07/47] writeback: account per-bdi accumulated written pages Wu Fengguang
2010-12-13 6:42 ` [PATCH 08/47] writeback: bdi write bandwidth estimation Wu Fengguang
2010-12-13 6:42 ` [PATCH 09/47] writeback: show bdi write bandwidth in debugfs Wu Fengguang
2010-12-13 6:42 ` [PATCH 10/47] writeback: quit throttling when bdi dirty pages dropped low Wu Fengguang
2010-12-13 6:43 ` [PATCH 11/47] writeback: reduce per-bdi dirty threshold ramp up time Wu Fengguang
2010-12-13 6:43 ` [PATCH 12/47] writeback: make reasonable gap between the dirty/background thresholds Wu Fengguang
2010-12-13 6:43 ` [PATCH 13/47] writeback: scale down max throttle bandwidth on concurrent dirtiers Wu Fengguang
2010-12-13 6:43 ` Wu Fengguang [this message]
2010-12-13 6:43 ` [PATCH 15/47] writeback: make nr_to_write a per-file limit Wu Fengguang
2010-12-13 6:43 ` [PATCH 16/47] writeback: make-nr_to_write-a-per-file-limit fix Wu Fengguang
2010-12-13 6:43 ` [PATCH 17/47] writeback: do uninterruptible sleep in balance_dirty_pages() Wu Fengguang
2010-12-13 6:43 ` [PATCH 18/47] writeback: move BDI_WRITTEN accounting into __bdi_writeout_inc() Wu Fengguang
2010-12-13 6:43 ` [PATCH 19/47] writeback: fix increasement of nr_dirtied_pause Wu Fengguang
2010-12-13 6:43 ` [PATCH 20/47] writeback: use do_div in bw calculation Wu Fengguang
2010-12-13 6:43 ` [PATCH 21/47] writeback: prevent divide error on tiny HZ Wu Fengguang
2010-12-13 6:43 ` [PATCH 22/47] writeback: prevent bandwidth calculation overflow Wu Fengguang
2010-12-13 6:43 ` [PATCH 23/47] writeback: spinlock protected bdi bandwidth update Wu Fengguang
2010-12-13 6:43 ` [PATCH 24/47] writeback: increase pause time on concurrent dirtiers Wu Fengguang
2010-12-13 6:43 ` [PATCH 25/47] writeback: make it easier to break from a dirty exceeded bdi Wu Fengguang
2010-12-13 6:43 ` [PATCH 26/47] writeback: start background writeback earlier Wu Fengguang
2010-12-13 6:43 ` [PATCH 27/47] writeback: user space think time compensation Wu Fengguang
2010-12-13 6:43 ` [PATCH 28/47] writeback: bdi base throttle bandwidth Wu Fengguang
2010-12-13 6:43 ` [PATCH 29/47] writeback: smoothed bdi dirty pages Wu Fengguang
2010-12-13 6:43 ` [PATCH 30/47] writeback: adapt max balance pause time to memory size Wu Fengguang
2010-12-13 6:43 ` [PATCH 31/47] writeback: increase min pause time on concurrent dirtiers Wu Fengguang
2010-12-13 6:43 ` [PATCH 32/47] writeback: extend balance_dirty_pages() trace event Wu Fengguang
2010-12-13 6:43 ` [PATCH 33/47] writeback: trace global dirty page states Wu Fengguang
2010-12-13 6:43 ` [PATCH 34/47] writeback: trace writeback_single_inode() Wu Fengguang
2010-12-13 6:43 ` [PATCH 35/47] writeback: scale IO chunk size up to device bandwidth Wu Fengguang
2010-12-13 6:43 ` [PATCH 36/47] btrfs: dont call balance_dirty_pages_ratelimited() on already dirty pages Wu Fengguang
2010-12-13 6:43 ` [PATCH 37/47] btrfs: lower the dirty balacing rate limit Wu Fengguang
2010-12-13 6:43 ` [PATCH 38/47] btrfs: wait on too many nr_async_bios Wu Fengguang
2010-12-13 6:43 ` [PATCH 39/47] nfs: livelock prevention is now done in VFS Wu Fengguang
2010-12-13 6:43 ` [PATCH 40/47] nfs: writeback pages wait queue Wu Fengguang
2010-12-13 6:43 ` [PATCH 41/47] nfs: in-commit pages accounting and " Wu Fengguang
2010-12-13 6:43 ` [PATCH 42/47] nfs: heuristics to avoid commit Wu Fengguang
2010-12-13 6:43 ` [PATCH 43/47] nfs: dont change wbc->nr_to_write in write_inode() Wu Fengguang
2010-12-13 6:43 ` [PATCH 44/47] nfs: limit the range of commits Wu Fengguang
2010-12-13 6:43 ` [PATCH 45/47] nfs: adapt congestion threshold to dirty threshold Wu Fengguang
2010-12-13 6:43 ` [PATCH 46/47] nfs: trace nfs_commit_unstable_pages() Wu Fengguang
2010-12-13 6:43 ` [PATCH 47/47] nfs: trace nfs_commit_release() Wu Fengguang
2010-12-13 11:27 ` [PATCH 00/47] IO-less dirty throttling v3 Peter Zijlstra
2010-12-13 11:49 ` Wu Fengguang
2010-12-13 12:38 ` Peter Zijlstra
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