Am Sonntag, den 19.10.2014, 21:35 +0200 schrieb Thomas Meyer:
> Am Sonntag, den 19.10.2014, 17:02 +0100 schrieb Anton Ivanov:
> > On 19/10/14 15:59, Thomas Meyer wrote:
> > > Am Dienstag, den 14.10.2014, 08:31 +0100 schrieb Anton Ivanov:
> > >> I see a very similar stall on writeout to ubd with my patches (easy) and
> > >> without (difficult - takes running an IO soak for a few days).
> > >>
> > >> It stalls (usually) when trying to flush the journal file of ext4.
> > > any ideas?
> >
> > I had some suspicion of a race somewhere in the UML VM subsystem. I
> > sprinked barrier() all over it, nope not the case.
> >
I added this patch to the uml kernel:
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 82e7db7..7f35fa4 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -241,6 +241,10 @@ static inline void __inc_zone_state(struct zone *zone,
enum zone_stat_item item)
static inline void __dec_zone_state(struct zone *zone, enum zone_stat_item
item)
{
atomic_long_dec(&zone->vm_stat[item]);
+ if (&vm_stat[item] == &vm_stat[NR_FILE_DIRTY] &&
+ atomic_long_read(&vm_stat[item]) < 0) {
+ asm("int3");
+ }
atomic_long_dec(&vm_stat[item]);
}
And this is the backtrace leading to the negative nr_dirty value:
Program received signal SIGTRAP, Trace/breakpoint trap.
__dec_zone_state (item=<optimized out>, zone=<optimized out>) at
include/linux/vmstat.h:248
(gdb) bt
#0 __dec_zone_state (item=<optimized out>, zone=<optimized out>) at
include/linux/vmstat.h:248
#1 __dec_zone_page_state (item=<optimized out>, page=<optimized out>) at
include/linux/vmstat.h:260
#2 clear_page_dirty_for_io (page=0x628b7308) at mm/page-writeback.c:2333
#3 0x0000000060188c36 in mpage_submit_page (mpd=0x808ebb90, page=<optimized
out>) at fs/ext4/inode.c:1785
#4 0x000000006018917e in mpage_map_and_submit_buffers (mpd=0x808ebb90) at
fs/ext4/inode.c:1981
#5 0x000000006018d64a in mpage_map_and_submit_extent
(give_up_on_write=<optimized out>, mpd=<optimized out>, handle=<optimized out>)
at fs/ext4/inode.c:2123
#6 ext4_writepages (mapping=<optimized out>, wbc=<optimized out>) at
fs/ext4/inode.c:2428
#7 0x00000000600f0838 in do_writepages (mapping=<optimized out>,
wbc=<optimized out>) at mm/page-writeback.c:2043
#8 0x0000000060143d29 in __writeback_single_inode (inode=0x75e191a8,
wbc=0x808ebcb8) at fs/fs-writeback.c:461
#9 0x0000000060144c00 in writeback_sb_inodes (sb=<optimized out>,
wb=0x80a92330, work=0x808ebe00) at fs/fs-writeback.c:688
#10 0x0000000060144e0e in __writeback_inodes_wb (wb=0x808eb990,
work=0x628b7308) at fs/fs-writeback.c:733
#11 0x0000000060144f8d in wb_writeback (wb=0x80a92330, work=0x808ebe00) at
fs/fs-writeback.c:864
#12 0x0000000060145375 in wb_check_old_data_flush (wb=<optimized out>) at
fs/fs-writeback.c:979
#13 wb_do_writeback (wb=<optimized out>) at fs/fs-writeback.c:1014
#14 bdi_writeback_workfn (work=0x808eb990) at fs/fs-writeback.c:1044
#15 0x00000000600690a2 in process_one_work (worker=0x808c3700, work=0x80a92340)
at kernel/workqueue.c:2023
#16 0x0000000060069b5e in worker_thread (__worker=0x808eb990) at
kernel/workqueue.c:2155
#17 0x000000006006dd9f in kthread (_create=0x80822040) at kernel/kthread.c:207
#18 0x000000006003ab59 in new_thread_handler () at arch/um/kernel/process.c:129
#19 0x0000000000000000 in ?? ()
------------------------------------------------------------------------------
Comprehensive Server Monitoring with Site24x7.
Monitor 10 servers for $9/Month.
Get alerted through email, SMS, voice calls or mobile push notifications.
Take corrective actions from your mobile device.
http://p.sf.net/sfu/Zoho
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
