From: Wu Fengguang <fengguang.wu@intel.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
Rik van Riel <riel@redhat.com>,
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: Mel Gorman <mel@csn.ul.ie>
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 22/47] writeback: prevent bandwidth calculation overflow
Date: Mon, 13 Dec 2010 14:43:11 +0800 [thread overview]
Message-ID: <20101213064839.658200254@intel.com> (raw)
In-Reply-To: 20101213064249.648862451@intel.com
[-- Attachment #1: writeback-prevent-bw-overflow.patch --]
[-- Type: text/plain, Size: 4239 bytes --]
On 32bit kernel, bdi->write_bandwidth can express at most 4GB/s.
However the current calculation code can overflow when disk bandwidth
reaches 800MB/s. Fix it by using "long long" and div64_u64() in the
calculations.
And further change its unit from bytes/second to pages/second.
That allows up to 16TB/s bandwidth in 32bit kernel.
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/linux/backing-dev.h | 5 +++--
mm/backing-dev.c | 4 ++--
mm/page-writeback.c | 14 +++++++-------
3 files changed, 12 insertions(+), 11 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-12-08 22:44:28.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-12-08 22:44:29.000000000 +0800
@@ -531,7 +531,7 @@ void bdi_update_write_bandwidth(struct b
unsigned long written;
unsigned long elapsed;
unsigned long bw;
- unsigned long w;
+ unsigned long long w;
if (*bw_written == 0)
goto snapshot;
@@ -550,9 +550,10 @@ void bdi_update_write_bandwidth(struct b
goto snapshot;
written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]) - *bw_written;
- bw = (HZ * PAGE_CACHE_SIZE * written + elapsed/2) / elapsed;
+ bw = (HZ * written + elapsed / 2) / elapsed;
w = min(elapsed / unit_time, 128UL);
- bdi->write_bandwidth = (bdi->write_bandwidth * (1024-w) + bw * w) >> 10;
+ bdi->write_bandwidth = (bdi->write_bandwidth * (1024-w) +
+ bw * w + 1023) >> 10;
bdi->write_bandwidth_update_time = jiffies;
snapshot:
*bw_written = percpu_counter_read(&bdi->bdi_stat[BDI_WRITTEN]);
@@ -577,7 +578,7 @@ static void balance_dirty_pages(struct a
unsigned long dirty_thresh;
unsigned long bdi_thresh;
unsigned long task_thresh;
- unsigned long bw;
+ unsigned long long bw;
unsigned long pause = 0;
bool dirty_exceeded = false;
struct backing_dev_info *bdi = mapping->backing_dev_info;
@@ -640,8 +641,7 @@ static void balance_dirty_pages(struct a
* of dirty pages have been cleaned during our pause time.
*/
if (nr_dirty < dirty_thresh &&
- bdi_prev_dirty - bdi_dirty >
- bdi->write_bandwidth >> (PAGE_CACHE_SHIFT + 2))
+ bdi_prev_dirty - bdi_dirty > (long)bdi->write_bandwidth / 4)
break;
bdi_prev_dirty = bdi_dirty;
@@ -664,7 +664,7 @@ static void balance_dirty_pages(struct a
bw = bw * (task_thresh - bdi_dirty);
do_div(bw, bdi_thresh / TASK_SOFT_DIRTY_LIMIT + 1);
- pause = HZ * (pages_dirtied << PAGE_CACHE_SHIFT) / (bw + 1);
+ pause = HZ * pages_dirtied / ((unsigned long)bw + 1);
pause = clamp_val(pause, 1, HZ/10);
pause:
--- linux-next.orig/mm/backing-dev.c 2010-12-08 22:44:24.000000000 +0800
+++ linux-next/mm/backing-dev.c 2010-12-08 22:44:29.000000000 +0800
@@ -103,7 +103,7 @@ static int bdi_debug_stats_show(struct s
(unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
K(bdi_thresh), K(dirty_thresh), K(background_thresh),
(unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),
- (unsigned long) bdi->write_bandwidth >> 10,
+ (unsigned long) K(bdi->write_bandwidth),
nr_dirty, nr_io, nr_more_io,
!list_empty(&bdi->bdi_list), bdi->state);
#undef K
@@ -662,7 +662,7 @@ int bdi_init(struct backing_dev_info *bd
goto err;
}
- bdi->write_bandwidth = 100 << 20;
+ bdi->write_bandwidth = (100 << 20) / PAGE_CACHE_SIZE;
bdi->dirty_exceeded = 0;
err = prop_local_init_percpu(&bdi->completions);
--- linux-next.orig/include/linux/backing-dev.h 2010-12-08 22:44:24.000000000 +0800
+++ linux-next/include/linux/backing-dev.h 2010-12-08 22:44:29.000000000 +0800
@@ -74,9 +74,10 @@ struct backing_dev_info {
struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
- struct prop_local_percpu completions;
+ unsigned long write_bandwidth;
unsigned long write_bandwidth_update_time;
- int write_bandwidth;
+
+ struct prop_local_percpu completions;
int dirty_exceeded;
unsigned int min_ratio;
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
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 ` [PATCH 14/47] writeback: add trace event for balance_dirty_pages() Wu Fengguang
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 ` Wu Fengguang [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20101213064839.658200254@intel.com \
--to=fengguang.wu@intel.com \
--cc=a.p.zijlstra@chello.nl \
--cc=akpm@linux-foundation.org \
--cc=jack@suse.cz \
--cc=riel@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).