Re: dentry bloat.
From: Andrew Morton
Date: Tue May 11 2004 - 15:25:33 EST
Maneesh Soni <maneesh@xxxxxxxxxx> wrote:
> We can see this happening in the following numbers taken using dcachebench*
> gathered on 2-way P4 Xeon 2.4MHz SMP box with 4.5GB RAM. The benchmark was run
> with the following parameters and averaged over 10 runs.
> ./dcachebench -p 32 -b testdir
> Average microseconds/iterations Std. Deviation
> (lesser is better)
> 2.6.6 10204 161.5
> 2.6.6-mm1 10571 51.5
Well.. this could be anything. If the hash is any good -mm shouldn't be
doing significantly more locked operations. (I think - didn't check very
Also the inode and dentry hash algorithms were changed in -mm. You can
evaluate the effect of that by comparing 2.6.6 with current Linus -bk.
If we compare 2.6.6-bk with 2.6.6-mm1 and see a slowdown on SMP and no
slowdown on UP then yup, it might be due to additional locking.
But we should evaluate the hash changes separately.
2.6.6: dentry size+alignment changes
2.6.6-bk: dentry size+alignment changes, hash changes
2.6.6-mm1: dentry size+alignment changes, hash changes, lots of other stuff.
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