Re: [PATCH] Rmap speedup

Daniel Phillips
2002-08-03T22:44:31Z

On Saturday 03 August 2002 23:40, Andrew Morton wrote:
> - total amount of CPU time lost spinning on locks is 1%, mainly
> in page_add_rmap and zap_pte_range.
>
> That's not much spintime. The total system time with this test went
> from 71 seconds (2.5.26) to 88 seconds (2.5.30). (4.5 seconds per CPU)
> So all the time is presumably spent waiting on cachelines to come from
> other CPUs, or from local L2.

Have we tried this one:

static inline unsigned rmap_lockno(pgoff_t index)
{
- return (index >> 4) & (ARRAY_SIZE(rmap_locks) - 1);
+ return (index >> 4) & (ARRAY_SIZE(rmap_locks) - 16);
}

(which puts all the rmap spinlocks in separate cache lines)

--
Daniel