Re: [patchset] Lockfree fd lookup 0 of 5

Dipankar Sarma
2004-08-03T10:21:31Z

On Tue, Aug 03, 2004 at 03:05:55PM +0530, Ravikiran G Thirumalai wrote:
> On Tue, Aug 03, 2004 at 02:53:17PM +0530, Ravikiran G Thirumalai wrote:
> > I ran tiobench on this patch and here is the comparison:
> >
> >
> > Kernel Seqread Randread Seqwrite Randwrite
> > --------------------------------------------------------------------------
> > 2.6.7 410.33 234.15 254.39 189.36
> > rwlocks-viro 401.84 232.69 254.09 194.62
> > refcount (kref) 455.72 281.75 272.87 230.10
> >

Hm...

11514 6.7783 fget_light (vanilla)
13168 7.7224 fget_light (rwlock)
1993 1.2633 fget_light (kref)

Total ticks -

169886 (vanilla)
170520 (rwlock)
157760 (kref)

Of the 12126 ticks that were reduced by kref, 9521 came from
reduction in fget_light(). So, lock-free fget_light() does help.
Also, it seems the lock contention is not much of an issue -

1203 0.7082 .text.lock.file_table

That explains why rwlock didn't help. I guess we are benefiting
mostly from avoiding the cacheline bouncing and removal of the
lock acquisition.

Thanks
Dipankar