Re: 2.6.24-rc1 - Regularly getting processes stuck in D state onstartup
From: Fengguang Wu
Date: Tue Nov 06 2007 - 03:00:27 EST
On Mon, Nov 05, 2007 at 06:23:07PM +0000, David wrote:
> I've been testing rc1 for a week or so, and about 25% of the time I'm
> seeing Firefox and Thunderbird getting stuck in 'D' state as they startup.
>
> I've attached the output of Sysrq-T to this mail... system is a
> dual-core AMD64, and files are on a RAID-1 root partition connected two
> SATA disks on the on-board NVidia controller. I've had no problems
> before .24 rc1
David, thank you for the reporting.
Could you try with the attached 4 patches? Two of them are expected to
fix your problem, another two are debugging ones(in case the problem
persists).
Thank you,
Fengguang
Subject: reiserfs: fix writeback
Reiserfs could leave newly created sub-page-size files in dirty state for ever.
They cannot be synced to disk by pdflush routines or an explicit `sync' command.
Only `umount' can do the trick.
This is not a new issue in 2.6.23-git17. 2.6.23 is buggy in the same way.
The direct cause is, the dirty page's PG_dirty is cleared on
reiserfs_file_release(). Call trace:
[<ffffffff8027e920>] cancel_dirty_page+0xd0/0xf0
[<ffffffff8816d470>] :reiserfs:reiserfs_cut_from_item+0x660/0x710
[<ffffffff8816d791>] :reiserfs:reiserfs_do_truncate+0x271/0x530
[<ffffffff8815872d>] :reiserfs:reiserfs_truncate_file+0xfd/0x3b0
[<ffffffff8815d3d0>] :reiserfs:reiserfs_file_release+0x1e0/0x340
[<ffffffff802a187c>] __fput+0xcc/0x1b0
[<ffffffff802a1ba6>] fput+0x16/0x20
[<ffffffff8029e676>] filp_close+0x56/0x90
[<ffffffff8029fe0d>] sys_close+0xad/0x110
[<ffffffff8020c41e>] system_call+0x7e/0x83
Fix the problem by simply removing the cancel_dirty_page() call.
Here are more detailed demonstrations of the problem:
1) the page has both PG_dirty(D)/PAGECACHE_TAG_DIRTY(d) after being written to;
and then only PAGECACHE_TAG_DIRTY(d) remains after the file is closed.
------------------------------ screen 0 ------------------------------
[T0] root /home/wfg# cat > /test/tiny
[T1] hi
[T2] root /home/wfg#
------------------------------ screen 1 ------------------------------
[T1] root /home/wfg# echo /test/tiny > /proc/filecache
[T1] root /home/wfg# cat /proc/filecache
# file /test/tiny
# flags R:referenced A:active M:mmap U:uptodate D:dirty W:writeback O:owner B:buffer d:dirty w:writeback
# idx len state refcnt
0 1 ___UD__Bd_ 2
[T2] root /home/wfg# cat /proc/filecache
# file /test/tiny
# flags R:referenced A:active M:mmap U:uptodate D:dirty W:writeback O:owner B:buffer d:dirty w:writeback
# idx len state refcnt
0 1 ___U___Bd_ 2
2) note the non-zero `cancelled_write_bytes' after /tmp/hi is copied.
------------------------------ screen 0 ------------------------------
[T0] root /home/wfg# echo hi > /tmp/hi
[T1] root /home/wfg# cp /tmp/hi /dev/stdin /test
[T2] hi
[T3] root /home/wfg#
------------------------------ screen 1 ------------------------------
[T1] root /proc/4397# cd /proc/`pidof cp`
[T1] root /proc/4713# cat io
rchar: 8396
wchar: 3
syscr: 20
syscw: 1
read_bytes: 0
write_bytes: 20480
cancelled_write_bytes: 4096
[T2] root /proc/4713# cat io
rchar: 8399
wchar: 6
syscr: 21
syscw: 2
read_bytes: 0
write_bytes: 24576
cancelled_write_bytes: 4096
Cc: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
fs/reiserfs/stree.c | 3 ---
1 file changed, 3 deletions(-)
--- linux-2.6.24-git17.orig/fs/reiserfs/stree.c
+++ linux-2.6.24-git17/fs/reiserfs/stree.c
@@ -1458,9 +1458,6 @@ static void unmap_buffers(struct page *p
}
bh = next;
} while (bh != head);
- if (PAGE_SIZE == bh->b_size) {
- cancel_dirty_page(page, PAGE_CACHE_SIZE);
- }
}
}
}
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Subject: mm: speed up writeback ramp-up on clean systems
We allow violation of bdi limits if there is a lot of room on the
system. Once we hit half the total limit we start enforcing bdi limits
and bdi ramp-up should happen. Doing it this way avoids many small
writeouts on an otherwise idle system and should also speed up the
ramp-up.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
mm/page-writeback.c | 19 +++++++++++++++++--
1 file changed, 17 insertions(+), 2 deletions(-)
--- linux-2.6.24-git17.orig/mm/page-writeback.c
+++ linux-2.6.24-git17/mm/page-writeback.c
@@ -355,8 +355,8 @@ get_dirty_limits(long *pbackground, long
*/
static void balance_dirty_pages(struct address_space *mapping)
{
- long bdi_nr_reclaimable;
- long bdi_nr_writeback;
+ long nr_reclaimable, bdi_nr_reclaimable;
+ long nr_writeback, bdi_nr_writeback;
long background_thresh;
long dirty_thresh;
long bdi_thresh;
@@ -376,11 +376,26 @@ static void balance_dirty_pages(struct a
get_dirty_limits(&background_thresh, &dirty_thresh,
&bdi_thresh, bdi);
+
+ nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
+ global_page_state(NR_UNSTABLE_NFS);
+ nr_writeback = global_page_state(NR_WRITEBACK);
+
bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+
if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh)
break;
+ /*
+ * Throttle it only when the background writeback cannot
+ * catch-up. This avoids (excessively) small writeouts
+ * when the bdi limits are ramping up.
+ */
+ if (nr_reclaimable + nr_writeback <
+ (background_thresh + dirty_thresh) / 2)
+ break;
+
if (!bdi->dirty_exceeded)
bdi->dirty_exceeded = 1;
---
mm/page-writeback.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
--- linux-2.6.23-rc8-mm2.orig/mm/page-writeback.c
+++ linux-2.6.23-rc8-mm2/mm/page-writeback.c
@@ -98,6 +98,26 @@ EXPORT_SYMBOL(laptop_mode);
/* End of sysctl-exported parameters */
+#define writeback_debug_report(n, wbc) do { \
+ __writeback_debug_report(n, wbc, __FILE__, __LINE__, __FUNCTION__); \
+} while (0)
+
+void __writeback_debug_report(long n, struct writeback_control *wbc,
+ const char *file, int line, const char *func)
+{
+ printk("%s %d %s: %s(%d) %ld "
+ "global %lu %lu %lu "
+ "wc %c%c tw %ld sk %ld\n",
+ file, line, func,
+ current->comm, current->pid, 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);
+}
static void background_writeout(unsigned long _min_pages);
@@ -404,6 +424,7 @@ 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);
}
/*
@@ -568,6 +589,7 @@ static void background_writeout(unsigned
wbc.pages_skipped = 0;
writeback_inodes(&wbc);
min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
+ writeback_debug_report(min_pages, &wbc);
if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
/* Wrote less than expected */
if (wbc.encountered_congestion)
@@ -643,6 +665,7 @@ static void wb_kupdate(unsigned long arg
wbc.encountered_congestion = 0;
wbc.nr_to_write = MAX_WRITEBACK_PAGES;
writeback_inodes(&wbc);
+ writeback_debug_report(nr_to_write, &wbc);
if (wbc.nr_to_write > 0) {
if (wbc.encountered_congestion)
congestion_wait(WRITE, HZ/10);
Subject: track redirty_tail() calls
It helps a lot to know how redirty_tail() are called.
Cc: Ken Chen <kenchen@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
fs/fs-writeback.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
--- linux-2.6.24-git17.orig/fs/fs-writeback.c
+++ linux-2.6.24-git17/fs/fs-writeback.c
@@ -164,12 +164,26 @@ static void redirty_tail(struct inode *i
list_move(&inode->i_list, &sb->s_dirty);
}
+#define requeue_io(inode) \
+ do { \
+ __requeue_io(inode, __LINE__); \
+ } while (0)
+
/*
* requeue inode for re-scanning after sb->s_io list is exhausted.
*/
-static void requeue_io(struct inode *inode)
+static void __requeue_io(struct inode *inode, int line)
{
list_move(&inode->i_list, &inode->i_sb->s_more_io);
+
+ printk(KERN_DEBUG "requeue_io %d: inode %lu size %llu at %02x:%02x(%s)\n",
+ line,
+ inode->i_ino,
+ i_size_read(inode),
+ MAJOR(inode->i_sb->s_dev),
+ MINOR(inode->i_sb->s_dev),
+ inode->i_sb->s_id
+ );
}
static void inode_sync_complete(struct inode *inode)