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    SubjectRe: shrinkable cache statistics [was Re: VM balancing issues on 2.6.13: dentry cache not getting shrunk enough]
    On Wed, Oct 05, 2005 at 06:25:51PM -0300, Marcelo Tosatti wrote:
    > Hi Bharata,
    >
    > On Tue, Oct 04, 2005 at 07:06:35PM +0530, Bharata B Rao wrote:
    > > Marcelo,
    > >
    > > Here's my next attempt in breaking the "slabs_scanned" from /proc/vmstat
    > > into meaningful per cache statistics. Now I have the statistics counters
    > > as percpu. [an issue remaining is that there are more than one cache as
    > > part of mbcache and they all have a common shrinker routine and I am
    > > displaying the collective shrinker stats info on each of them in
    > > /proc/slabinfo ==> some kind of duplication]
    >
    > Looks good to me! IMO it should be a candidate for -mm/mainline.
    >
    > Nothing useful to suggest on the mbcache issue... sorry.

    Thanks Marcelo for reviewing.

    <snip>

    > >
    > > [root@llm09 bharata]# grep shrinker /proc/slabinfo
    > > # name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab> : tunables <limit> <batchcount> <sharedfactor> : slabdata <active_slabs> <num_slabs> <sharedavail> : shrinker stat <nr requested> <nr freed>
    > > ext3_xattr 0 0 48 78 1 : tunables 120 60 8 : slabdata 0 0 0 : shrinker stat 0 0
    > > dquot 0 0 160 24 1 : tunables 120 60 8 : slabdata 0 0 0 : shrinker stat 0 0
    > > inode_cache 1301 1390 400 10 1 : tunables 54 27 8 : slabdata 139 139 0 : shrinker stat 682752 681900
    > > dentry_cache 82110 114452 152 26 1 : tunables 120 60 8 : slabdata 4402 4402 0 : shrinker stat 1557760 760100
    > >
    > > [root@llm09 bharata]# grep slabs_scanned /proc/vmstat
    > > slabs_scanned 2240512
    > >
    > > [root@llm09 bharata]# cat /proc/sys/fs/dentry-state
    > > 82046 75369 45 0 3599 0
    > > [The order of dentry-state o/p is like this:
    > > total dentries in dentry hash list, total dentries in lru list, age limit,
    > > want_pages, inuse dentries in lru list, dummy]
    > >
    > > So, we can see that with low memory pressure, even though the
    > > shrinker runs on dcache repeatedly, not many dentries are freed
    > > by dcache. And dcache lru list still has huge number of free
    > > dentries.
    >
    > The success/attempt ratio is about 1/2, which seems alright?
    >

    Hmm... when compared to inode_cache, I felt dcache shrinker wasn't
    doing a good job. Anyway I will analyze further to see if things
    can be made better with the existing shrinker.

    Regards,
    Bharata.
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