On Thu, 26 Jul 2007 14:46:58 +0200 Mike Galbraith <[email protected]> wrote:
> On Thu, 2007-07-26 at 03:09 -0700, Andrew Morton wrote:
>
> > Setting it to zero will maximise the preservation of the vfs caches. You
> > wanted 10000 there.
> >
> > <bets that nobody will test this>
>
> drops caches prior to both updatedb runs.
I think that was the wrong thing to do. That will leave gobs of free
memory for updatedb to populate with dentries and inodes.
Instead, fill all of memory up with pagecache, then do the updatedb. See
how much pagecache is left behind and see how large the vfs caches end up.
> root@Homer: df -i
> Filesystem Inodes IUsed IFree IUse% Mounted on
> /dev/hdc3 12500992 1043544 11457448 9% /
> udev 129162 1567 127595 2% /dev
> /dev/hdc1 26104 87 26017 1% /boot
> /dev/hda1 108144 90676 17468 84% /windows/C
> /dev/hda5 11136 3389 7747 31% /windows/D
> /dev/hda6 0 0 0 - /windows/E
>
> vfs_cache_pressure=10000, updatedb freshly completed:
> procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 1 0 48 76348 420356 104748 0 0 0 0 1137 912 3 1 97 0
>
> ext3_inode_cache 315153 316274 524 7 1 : tunables 54 27 8 : slabdata 45182 45182 0
> dentry_cache 224829 281358 136 29 1 : tunables 120 60 8 : slabdata 9702 9702 0
> buffer_head 156624 159728 56 67 1 : tunables 120 60 8 : slabdata 2384 2384 0
>
> vfs_cache_pressure=100 (stock), updatedb freshly completed:
>
> procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 1 0 148 83824 270088 116340 0 0 0 0 1095 330 2 1 97 0
>
> ext3_inode_cache 467257 502495 524 7 1 : tunables 54 27 8 : slabdata 71785 71785 0
> dentry_cache 292695 408958 136 29 1 : tunables 120 60 8 : slabdata 14102 14102 0
> buffer_head 118329 184384 56 67 1 : tunables 120 60 8 : slabdata 2752 2752 1
>
> Note: updatedb doesn't bother my box, not running enough leaky apps I
> guess.
>
So you ended up with a couple hundred MB of pagecache preserved.
Capturing before-and-after /proc/meminfo would be nice - it's a useful
summary.
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