Re: [PATCH 0/6] files: scalable fd management (V4)

[Dipankar Sarma <dipankar@in.ibm.com>]

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