From: Tim Deegan <tim@xen.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Malcolm Crossley <malcolm.crossley@citrix.com>,
xen-devel@lists.xensource.com
Subject: Re: heap_lock optimizations?
Date: Mon, 15 Jul 2013 17:09:40 +0100 [thread overview]
Message-ID: <20130715160940.GA6719@ocelot.phlegethon.org> (raw)
In-Reply-To: <20130715151525.GG4817@phenom.dumpdata.com>
Hi,
At 11:15 -0400 on 15 Jul (1373886925), Konrad Rzeszutek Wilk wrote:
> Hey Tim,
>
> I was looking at making the 'Scrubbing Free RAM:' code faster on 1TB
> boxes with 128 CPUs. And naively I wrote code that setup a tasklet
> on each CPU and scrub a swatch of MFNs. Unfortunatly even on 8VCPU
> machines the end result was a slower boot time!
>
> The culprit looks to be the heap_lock that is taken and released
> on every MFN (for fun I added a bit of code to do batches - of
> 32 MFNs and to iterate over those 32 MFNs while holding the lock - that
> did make it a bit faster, but not by a much).
>
> What I am wondering is:
> - Have you ever thought about optimizing this? If so, how?
Malcolm Crossley posted an RFC patch a while ago to do this kind of
stuff -- parcelled out RAM to socket-local CPUs and IIRC took the
heap-lock once for all on the coordinating CPU.
http://lists.xen.org/archives/html/xen-devel/2012-05/msg00701.html
AIUI he's going to send a v2 now that 4.3 is done.
Tim.
prev parent reply other threads:[~2013-07-15 16:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-15 15:15 heap_lock optimizations? Konrad Rzeszutek Wilk
2013-07-15 15:46 ` Malcolm Crossley
2013-07-15 16:14 ` Konrad Rzeszutek Wilk
2013-07-16 16:41 ` Konrad Rzeszutek Wilk
2013-07-15 16:09 ` Tim Deegan [this message]
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