Re: [PATCH] scrub pages on guest termination

[Ben Guthro <bguthro@virtualiron.com>]

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Yes, sorry -  should have removed our terminology from the description.
Node=physical machine
VS=HVM guest w/ pv-on-hvm drivers
Looking back at the original bug report - it seems to indicate it was 
migrating from a system with 2 processors to one with 8

Specifcally - from
Dell Precision WorkStation 380
Processor:    Intel(R) Pentium(R) D CPU 2.80GHz
# of CPUs:    2
Speed:    2.8GHz

to

Supermicro X7DB8
Processor:    Genuine Intel(R) CPU @ 2.13GHz
# of CPUs:    8
Speed:    2.133 GHz




Keir Fraser wrote:
> The aim of the loop was to scrub enough pages in a batch that lock 
> contention is kept tolerably low. Even if 16 pages is not sufficient 
> for that, I'm surprised a 'node' (you mean a whole system, 
> presumably?) would appear to lock up. Maybe pages would be scrubbed 
> slower than we'd like, but still CPUs should be able to get the 
> spinlock often enough to evaluate whether they have spent 1ms in the 
> loop and hence get out of there.
>
> What sort of system were you seeing the lockup on? Does it have very 
> many physical CPUs?
>
>  -- Keir
>
> On 23/5/08 16:00, "Ben Guthro" <bguthro@virtualiron.com> wrote:
>
>     This patch solves the following problem.  When a large VS
>     terminates, the node locks
>     up. The node locks up because the page_scrub_kick routine sends a
>     softirq to
>     all processors instructing them to run the page scrub code.  There
>     they interfere
>     with each other as they serialize behind the page_scrub_lock.
>
>


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