Re: Latest vfs scalability patch

[Jens Axboe <jens.axboe@oracle.com>]

On Tue, Oct 06 2009, Nick Piggin wrote:
> Hi,
> 
> Several people have been interested to test my vfs patches, so rather
> than resend patches I have uploaded a rollup against Linus's current
> head.
> 
> ftp://ftp.kernel.org/pub/linux/kernel/people/npiggin/patches/fs-scale/
> 
> I have used ext2,ext3,autofs4,nfs as well as in-memory filesystems
> OK (although this doesn't mean there are no bugs!). Otherwise, if your
> filesystem compiles, then there is a reasonable chance of it working,
> or ask me and I can try updating it for the new locking.
> 
> I would be interested in seeing any numbers people might come up with,
> including single-threaded performance.

I gave this a quick spin on the 64-thread nehalem. Just a simple dbench
with 64 clients on tmpfs. The results are below. While running perf top
-a in mainline, the top 5 entries are:

          2086691.00 - 96.6% : _spin_lock
            14866.00 -  0.7% : copy_user_generic_string
             5710.00 -  0.3% : mutex_spin_on_owner
             2837.00 -  0.1% : _atomic_dec_and_lock
             2274.00 -  0.1% : __d_lookup

Uhm auch... It doesn't look much prettier for the patch kernel, though:

          9396422.00 - 95.7% : _spin_lock
            66978.00 -  0.7% : copy_user_generic_string
            43775.00 -  0.4% : dput
            23946.00 -  0.2% : __link_path_walk
            17699.00 -  0.2% : path_init
            15046.00 -  0.2% : do_lookup


Anyway, below are the results. Seem very stable.

                                throughput
------------------------------------------------
2.6.32-rc3-git          |      561.218 MB/sec
2.6.32-rc3-git+patch    |      627.022 MB/sec


-- 
Jens Axboe