Re: [PATCH] Prezeroing V8
From: Christoph Lameter
Date: Thu Mar 17 2005 - 19:08:03 EST
On Thu, 17 Mar 2005, Andrew Morton wrote:
> > http://oss.sgi.com/projects/page_fault_performance/
> Oh no, not that page again ;)
> Seems to say that prezeroing makes negligible difference to kernel builds,
> but speeds up a big malloc+memset by 3x to 4x, yes?
> Are there any real-worldish workloads which show an appreciable benefit?
Ummm. Big loads are our real-worldish workloads here.
> The large speedup for a big memset seems odd - I assume it's simply
> transferring CPU load from the user's process over to kscrubd. Or is it
> the fancy page-zeroing hardware? How do we differentiate the two?
I switched off the page-zeroing hardware for the tests.
> Are there any workloads which are seeing a benefit on a CPU which doesn't
> have the zeroing hardware?
Without zeroing hardware the eroing actions are moved to idle
system time (load < /proc/sys/vm/scrub_load). Its shifting the cpu load.
But I just fixed things up so that the kernel can return hot zeroed
pages to the pool for quicklist management. This yields zeroed pages
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