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SubjectRe: 2.5.33-mm1
William Lee Irwin III wrote:
>
> On Mon, Sep 02, 2002 at 09:16:44PM -0700, Andrew Morton wrote:
> > http://www.zip.com.au/~akpm/linux/patches/2.5/2.5.33/2.5.33-mm1/
> > Seven new patches - mostly just code cleanups.
> > +slablru-speedup.patch
> > A patch to improve slablru cpu efficiency. Ed is
> > redoing this.
>
> count_list() appears to be the largest consumer of cpu after this is
> done, or so say the profiles after running updatedb by hand on
> 2.5.33-mm1 on a 900MHz P-III T21 Thinkpad with 256MB of RAM.

That's my /proc/meminfo:buffermem counter-upper. I said it would suck ;)
Probably count_list(&inode_unused) can just be nuked. I don't think blockdev
inodes ever go onto inode_unused.

> 4608 __rdtsc_delay 164.5714
> 2627 __generic_copy_to_user 36.4861
> 2401 count_list 42.8750
> 1415 find_inode_fast 29.4792
> 1325 do_anonymous_page 3.3801
>
> It also looks like there's either a bit of internal fragmentation or a
> missing kmem_cache_reap() somewhere:
>
> ext3_inode_cache: 20001KB 51317KB 38.97
> dentry_cache: 4734KB 18551KB 25.52
> radix_tree_node: 1811KB 1923KB 94.20
> buffer_head: 1132KB 1378KB 82.12

That's really outside the control of slablru. It's determined
by the cache-specific LRU algorithms, and the allocation order.

You'll need to look at the second-last and third-last columns in
/proc/slabinfo (boy I wish that thing had a heading line, or a nice
program to interpret it):

ext3_inode_cache 959 2430 448 264 270 1

That's 264 pages in use, 270 total. If there's a persistent gap between
these then there is a problem - could well be that slablru is not locating
the pages which were liberated by the pruning sufficiently quickly.

Calling kmem_cache_reap() after running the pruners will fix that up.
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