Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754493AbZISD6r (ORCPT ); Fri, 18 Sep 2009 23:58:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752967AbZISD6q (ORCPT ); Fri, 18 Sep 2009 23:58:46 -0400 Received: from mga14.intel.com ([143.182.124.37]:21216 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbZISD6p (ORCPT ); Fri, 18 Sep 2009 23:58:45 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,413,1249282800"; d="scan'208";a="189371281" Date: Sat, 19 Sep 2009 11:58:35 +0800 From: Wu Fengguang To: Theodore Tso , Jens Axboe , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "chris.mason@oracle.com" , "akpm@linux-foundation.org" , "jack@suse.cz" Subject: Re: [PATCH 0/7] Per-bdi writeback flusher threads v20 Message-ID: <20090919035835.GA9921@localhost> References: <1252654450-25721-1-git-send-email-jens.axboe@oracle.com> <20090911134241.GB19707@mit.edu> <20090911141659.GA3508@infradead.org> <20090911142926.GI14984@kernel.dk> <20090911143929.GA25499@localhost> <20090918175252.GF26991@mit.edu> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8t9RHnE3ZwKMSgU+" Content-Disposition: inline In-Reply-To: <20090918175252.GF26991@mit.edu> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 10336 Lines: 261 --8t9RHnE3ZwKMSgU+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sat, Sep 19, 2009 at 01:52:52AM +0800, Theodore Tso wrote: > On Fri, Sep 11, 2009 at 10:39:29PM +0800, Wu Fengguang wrote: > > > > That would be good. Sorry for the late work. I'll allocate some time > > in mid next week to help review and benchmark recent writeback works, > > and hope to get things done in this merge window. > > Did you have some chance to get more work done on the your writeback > patches? Sorry for the delay, I'm now testing the patches with commands cp /dev/zero /mnt/test/zero0 & dd if=/dev/zero of=/mnt/test/zero1 & and the attached debug patch. One problem I found with ext3/4 is, redirty_tail() is called repeatedly in the traces, which could slow down the inode writeback significantly. Ideal is to call requeue_[partial_]io() instead of redirty_tail(). [ 131.963885] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=0 [ 131.966171] global dirty=4105 writeback=18793 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0 [ 132.780826] fs/fs-writeback.c +809 wb_writeback(): comm=flush-0:15 pid=1150 n=0 [ 132.783097] global dirty=4105 writeback=16623 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0 [ 134.307094] redirty_tail() +542: inode=12 [ 134.815776] redirty_tail() +542: inode=13 [ 134.817709] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11493 [ 134.821242] global dirty=4192 writeback=16203 nfs=0 flags=__ towrite=21275 skipped=0 file=13 written=4430 [ 135.599954] redirty_tail() +542: inode=12 [ 136.372523] redirty_tail() +542: inode=13 [ 136.386748] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11570 [ 136.432168] global dirty=4308 writeback=15752 nfs=0 flags=__ towrite=21198 skipped=0 file=13 written=4650 [ 137.789115] fs/fs-writeback.c +809 wb_writeback(): comm=flush-0:15 pid=1150 n=0 [ 138.587178] global dirty=9551 writeback=10755 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0 [ 138.962743] redirty_tail() +542: inode=12 [ 139.395024] redirty_tail() +542: inode=13 [ 139.403194] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11893 [ 139.413026] global dirty=4101 writeback=16630 nfs=0 flags=__ towrite=20875 skipped=0 file=0 written=2 [ 139.426074] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=0 [ 139.435190] global dirty=4101 writeback=16378 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0 [ 140.266713] redirty_tail() +542: inode=12 [ 140.449304] redirty_tail() +542: inode=13 [ 140.496241] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11678 [ 140.508339] global dirty=4203 writeback=19220 nfs=0 flags=__ towrite=21090 skipped=0 file=13 written=4254 [ 141.649192] redirty_tail() +542: inode=12 [ 141.971276] redirty_tail() +542: inode=13 [ 141.988572] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=11304 [ 142.000107] global dirty=4112 writeback=18362 nfs=0 flags=__ towrite=21464 skipped=0 file=13 written=4541 btrfs pattern is almost the same, but with an extra (metadata) inode 1. [ 464.443873] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=0 [ 464.450458] global dirty=163 writeback=4375 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0 [ 464.655999] fs/fs-writeback.c +809 wb_writeback(): comm=flush-8:0 pid=2816 n=0 [ 464.664478] global dirty=3873 writeback=1175 nfs=0 flags=__ towrite=32768 skipped=0 file=0 written=0 [ 465.291059] redirty_tail() +542: inode=257 [ 465.331584] redirty_tail() +542: inode=258 [ 465.346433] redirty_tail() +560: inode=1 [ 465.352016] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=14480 [ 465.355797] global dirty=337 writeback=3980 nfs=0 flags=__ towrite=18288 skipped=0 file=1 written=0 [ 466.226489] redirty_tail() +542: inode=257 [ 466.280894] redirty_tail() +542: inode=258 [ 466.282270] redirty_tail() +560: inode=1 [ 466.288079] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=14300 [ 466.291738] global dirty=666 writeback=3807 nfs=0 flags=__ towrite=18468 skipped=0 file=1 written=0 [ 467.101730] redirty_tail() +542: inode=257 [ 467.134303] redirty_tail() +542: inode=258 [ 467.135675] redirty_tail() +560: inode=1 [ 467.144120] fs/fs-writeback.c +809 wb_writeback(): comm=flush-btrfs-1 pid=2865 n=14032 [ 467.147302] global dirty=331 writeback=3665 nfs=0 flags=__ towrite=18736 skipped=0 file=1 written=0 [ 467.964652] redirty_tail() +542: inode=257 [ 468.002423] redirty_tail() +542: inode=258 [ 468.003795] redirty_tail() +560: inode=1 I'm looking into it. Thanks, Fengguang --8t9RHnE3ZwKMSgU+ Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="writeback-debug.patch" fs/fs-writeback.c | 30 +++++++++++++++++++++++++++++- mm/page-writeback.c | 1 + 2 files changed, 30 insertions(+), 1 deletion(-) --- linux.orig/mm/page-writeback.c 2009-09-19 10:51:09.000000000 +0800 +++ linux/mm/page-writeback.c 2009-09-19 10:51:47.000000000 +0800 @@ -536,6 +536,7 @@ static void balance_dirty_pages(struct a pages_written += write_chunk - wbc.nr_to_write; get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi); + writeback_debug_report(pages_written, &wbc); } /* --- linux.orig/fs/fs-writeback.c 2009-09-19 10:51:46.000000000 +0800 +++ linux/fs/fs-writeback.c 2009-09-19 10:51:47.000000000 +0800 @@ -68,6 +68,33 @@ enum { #define WS_USED (1 << WS_USED_B) #define WS_ONSTACK (1 << WS_ONSTACK_B) +void print_writeback_control(struct writeback_control *wbc) +{ + printk(KERN_DEBUG + "global dirty=%lu writeback=%lu nfs=%lu " + "flags=%c%c towrite=%ld skipped=%ld " + "file=%lu written=%lu\n", + global_page_state(NR_FILE_DIRTY), + global_page_state(NR_WRITEBACK), + global_page_state(NR_UNSTABLE_NFS), + wbc->encountered_congestion ? 'C':'_', + wbc->more_io ? 'M':'_', + wbc->nr_to_write, + wbc->pages_skipped, + wbc->last_file, + wbc->last_file_written); +} + +void __writeback_debug_report(long n, struct writeback_control *wbc, + const char *file, int line, const char *func) +{ + printk(KERN_DEBUG "%s +%d %s(): comm=%s pid=%d n=%ld\n", + file, line, func, + current->comm, current->pid, + n); + print_writeback_control(wbc); +} + static inline bool bdi_work_on_stack(struct bdi_work *work) { return test_bit(WS_ONSTACK_B, &work->state); @@ -302,7 +329,7 @@ static void requeue_io(struct inode *ino */ static void requeue_partial_io(struct writeback_control *wbc, struct inode *inode) { - if (time_before(wbc->last_file_time + HZ, jiffies) || + if (time_before(wbc->last_file_time + 1000 * HZ, jiffies) || wbc->last_file_written == 0 || wbc->last_file_written >= MAX_WRITEBACK_PAGES) { requeue_io(inode); @@ -749,6 +776,7 @@ static long wb_writeback(struct bdi_writ args->nr_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; wrote += MAX_WRITEBACK_PAGES - wbc.nr_to_write; + writeback_debug_report(wrote, &wbc); /* * If we ran out of stuff to write, bail unless more_io got set */ --8t9RHnE3ZwKMSgU+ Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="requeue_io-debug.patch" Subject: track redirty_tail() calls It helps a lot to know how redirty_tail() are called. Cc: Ken Chen Cc: Andrew Morton Signed-off-by: Fengguang Wu --- fs/fs-writeback.c | 36 +++++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) --- linux.orig/fs/fs-writeback.c 2009-09-19 10:51:47.000000000 +0800 +++ linux/fs/fs-writeback.c 2009-09-19 10:52:03.000000000 +0800 @@ -290,6 +290,21 @@ void bdi_start_writeback(struct backing_ bdi_alloc_queue_work(bdi, &args); } +#define redirty_tail(inode) \ + do { \ + __redirty_tail(inode, __LINE__); \ + } while (0) + +#define requeue_io(inode) \ + do { \ + __requeue_io(inode, __LINE__); \ + } while (0) + +#define requeue_partial_io(wbc, inode) \ + do { \ + __requeue_partial_io(wbc, inode, __LINE__); \ + } while (0) + /* * Redirty an inode: set its when-it-was dirtied timestamp and move it to the * furthest end of its superblock's dirty-inode list. @@ -299,7 +314,7 @@ void bdi_start_writeback(struct backing_ * the case then the inode must have been redirtied while it was being written * out and we don't reset its dirtied_when. */ -static void redirty_tail(struct inode *inode) +static void __redirty_tail(struct inode *inode, int line) { struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; @@ -311,23 +326,33 @@ static void redirty_tail(struct inode *i inode->dirtied_when = jiffies; } list_move(&inode->i_list, &wb->b_dirty); + + if (sysctl_dirty_debug) { + printk(KERN_DEBUG "redirty_tail() +%d: inode=%lu\n", + line, inode->i_ino); + } } /* * requeue inode for re-scanning after bdi->b_io list is exhausted. */ -static void requeue_io(struct inode *inode) +static void __requeue_io(struct inode *inode, int line) { struct bdi_writeback *wb = &inode_to_bdi(inode)->wb; list_move(&inode->i_list, &wb->b_more_io); + + if (sysctl_dirty_debug) { + printk(KERN_DEBUG "requeue_io() +%d: inode=%lu\n", + line, inode->i_ino); + } } /* * continue io on this inode on next writeback if * it has not accumulated large enough writeback io chunk */ -static void requeue_partial_io(struct writeback_control *wbc, struct inode *inode) +static void __requeue_partial_io(struct writeback_control *wbc, struct inode *inode, int line) { if (time_before(wbc->last_file_time + 1000 * HZ, jiffies) || wbc->last_file_written == 0 || @@ -337,6 +362,11 @@ static void requeue_partial_io(struct wr } list_move_tail(&inode->i_list, &inode_to_bdi(inode)->wb.b_io); + + if (sysctl_dirty_debug) { + printk(KERN_DEBUG "requeue_partial_io() +%d: inode=%lu\n", + line, inode->i_ino); + } } static void inode_sync_complete(struct inode *inode) --8t9RHnE3ZwKMSgU+-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/