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SubjectRe: [PATCH 0/6] files: scalable fd management (V4)
Hello Andrew,

On Tue, Jun 14, 2005 at 01:03:38PM -0700, Andrew Morton wrote:
> Dipankar Sarma <dipankar@in.ibm.com> wrote:
> > tiobench on a 4-way ppc64 system :
> > (lockfree)
> > Test 2.6.10-vanilla Stdev 2.6.10-fd Stdev
> > -------------------------------------------------------------
> > Seqread 1428 32.47 1475.0 29.11
>
> We don't seem to have gained anything?

I repeated the measurements on ramfs (as opposed to ext2 on ramdisk in
the earlier measurement) and I got more consistent results from tiobench :

4(8) way xeon P4
-----------------
(lock-free)
Test 2.6.12-rc5 Stdev 2.6.12-rc5-fd Stdev
-------------------------------------------------------------
Seqread 1282 18.59 1343.6 26.37
Randread 1517 7 2415 34.27
Seqwrite 702.2 5.27 709.46 5.9
Randwrite 846.86 15.15 919.68 21.4


4-way ppc64
------------
(lock-free)
Test 2.6.12-rc5 Stdev 2.6.12-rc5-fd Stdev
-------------------------------------------------------------
Seqread 1549 91.16 1569.6 47.2
Randread 1473.6 25.11 1585.4 69.99
Seqwrite 1096.8 20.03 1136 29.61
Randwrite 1189.6 4.04 1275.2 32.96

Also running Tridge's thread_perf test on ppc64 :

2.6.12-rc5-vanilla
--------------------
Running test 'readwrite' with 4 tasks
Threads 0.20 +/- 0.02 seconds
Processes 0.16 +/- 0.01 seconds

2.6.12-rc5-fd
--------------------
Running test 'readwrite' with 4 tasks
Threads 0.18 +/- 0.04 seconds
Processes 0.16 +/- 0.01 seconds

The benefits are huge (upto ~60%) in some cases on x86 primarily
due to the atomic operations during acquisition of ->file_lock
and cache line bouncing in fast path. ppc64 benefits are modest
due to LL/SC based locking, but still statistically significant.

Thanks
Dipankar
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