Re: [Xen-devel] heap_lock optimizations?

[Tim Deegan <tim@xxxxxxx>]

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.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel