On Wed, Oct 10, 2012 at 06:07:22PM +0800, zwu.kernel@xxxxxxxxx wrote:
> From: Zhi Yong Wu <wuzhy@xxxxxxxxxxxxxxxxxx>
>
> NOTE:
>
> The patchset is currently post out mainly to make sure
> it is going in the correct direction and hope to get some
> helpful comments from other guys.
> For more infomation, please check hot_tracking.txt in Documentation
>
> TODO List:
1) Fix OOM issues - the hot inode tracking caches grow very large
and don't get trimmed under memory pressure. From slabtop, after
creating roughly 24 million single byte files(*) on a machine with
8GB RAM:
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
23859510 23859476 99% 0.12K 795317 30 3181268K hot_range_item
23859441 23859439 99% 0.16K 1037367 23 4149468K hot_inode_item
572530 572530 100% 0.55K 81790 7 327160K radix_tree_node
241706 241406 99% 0.22K 14218 17 56872K xfs_ili
241206 241204 99% 1.06K 80402 3 321608K xfs_inode
The inode tracking is trying to track all 24 million inodes even
though they have been written only once, and there are only 240,000
inodes in the cache at this point in time. That was the last update
that slabtop got, so it is indicative of the impending OOM situation
that occurred.
> Changelog from v2:
> 1.) Converted to Radix trees, not RB-tree [Zhiyong, Dave Chinner]
> 2.) Added memory shrinker [Dave Chinner]
I haven't looked at the shrinker, but clearly it is not working,
otherwise the above OOM situation would not be occurring.
Cheers,
Dave.
(*) Tested on an empty 17TB XFS filesystem with:
$ sudo mkfs.xfs -f -l size=131072b,sunit=8 /dev/vdc
meta-data=/dev/vdc isize=256 agcount=17, agsize=268435455 blks
= sectsz=512 attr=2, projid32bit=0
data = bsize=4096 blocks=4563402735, imaxpct=5
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal log bsize=4096 blocks=131072, version=2
= sectsz=512 sunit=1 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
$ sudo mount -o logbsize=256k /dev/vdc /mnt/scratch
$ sudo chmod 777 /mnt/scratch
$ fs_mark -D 10000 -S0 -n 100000 -s 1 -L 63 -d \
/mnt/scratch/0 -d /mnt/scratch/1 -d /mnt/scratch/2 -d \
/mnt/scratch/3 -d /mnt/scratch/4 -d /mnt/scratch/5 -d \
/mnt/scratch/6 -d /mnt/scratch/7
.....
0 21600000 1 16679.3 12552262
0 22400000 1 15412.4 12588587
0 23200000 1 16367.6 14199322
0 24000000 1 15680.4 15741205
<hangs here w/ OOM>
--
Dave Chinner
david@xxxxxxxxxxxxx
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