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-rc3: baseline
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.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at