Messages in this thread | | | Date | Tue, 22 Nov 2011 11:56:29 +0800 | From | Wu Fengguang <> | Subject | Re: [3.2-rc2] loop device balance_dirty_pages_nr throttling hang |
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Hi Dave,
On Mon, Nov 21, 2011 at 10:20:56PM +0800, Dave Chinner wrote: > Hi Fengguang, > > I just found a way of hanging a system and taking it down. I haven't > tried to narrow down the test case - it's pretty simple - because it > time for sleep here.
Yeah, once the global dirty limit is exceeded, the system would appear hang because many applications will block in balance_dirty_pages().
I created a script for this case, however cannot reproduce it..
The test box has 32GB memory and 110GB /dev/sda7, so I lowered the dirty_bytes=400MB and xfs "-b size=10g" explicitly in the script.
During the test run on 3.2.0-rc1, I find the dirty pages rarely exceed the background dirty threshold (200MB).
Would you try run this and see if this it's a problem of the test script?
root@snb /home/wfg# cat ./test-loop-fallocate.sh #!/bin/sh
# !!!change and uncomment this before run!!! # DEV=/dev/sda7
echo 1 > /debug/tracing/events/writeback/balance_dirty_pages/enable echo 1 > /debug/tracing/events/writeback/global_dirty_state/enable
echo $((400<<20)) > /proc/sys/vm/dirty_bytes mkfs.xfs -f -d size=10g $DEV mount $DEV /mnt/scratch xfs_io -f -c "truncate 20T" /mnt/scratch/scratch.img losetup /dev/loop0 /mnt/scratch/scratch.img mkfs.ext4 /dev/loop0 mkdir /mnt/scratch/scratch mount /dev/loop0 /mnt/scratch/scratch time xfs_io -f -F -c "truncate 15T " -c "falloc 0 15T" /mnt/scratch/scratch/foo umount /mnt/scratch/scratch losetup -d /dev/loop0 umount /mnt/scratch
root@snb /home/wfg# ./test-loop-fallocate.sh meta-data=/dev/sda7 isize=256 agcount=4, agsize=655360 blks = sectsz=512 attr=2, projid32bit=0 data = bsize=4096 blocks=2621440, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0 log =internal log bsize=4096 blocks=2560, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 mke2fs 1.42-WIP (16-Oct-2011) Discarding device blocks: done Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 335544320 inodes, 5368709120 blocks 268435456 blocks (5.00%) reserved for the super user First data block=0 163840 block groups 32768 blocks per group, 32768 fragments per group 2048 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968, 102400000, 214990848, 512000000, 550731776, 644972544, 1934917632, 2560000000, 3855122432
Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done
real 0m38.323s user 0m0.000s sys 0m25.203s
Thanks, Fengguang
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