Re: [Xen-devel] [PATCH v2] Xen: Spread boot time page scrubbing across all available CPU's

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 30/09/13 16:35, Jan Beulich wrote:
>>>> On 30.09.13 at 15:56, Malcolm Crossley <malcolm.crossley@xxxxxxxxxx> wrote:
>> The difference between 1 core per node bandwidth and 3 core's per node 
>> bandwidth is:
>>
>> AMD: 30000MB/s (1-core) vs 48000MB/s (3-core)
>> Intel: 12000MB/s (1-core) vs 38000MB/s (3-core)
>>
>> So I think it's worth the extra complexity to have multiple core's per 
>> node scrubbing memory.
> The numbers are convincing. Which means that the only request
> I'd have is to avoid more than one hyperthread on a core to get
> picked for doing the scrubbing.
>
> Jan
>

Why? Being independent operations, scrubbing like this will still be
sped up by hyperthreading.

As scrubbing RAM is simply a race to get it done as quickly as possible,
unless it can be demonstrated that using all cores is actively
detrimental to the overall time taken, we really should use all cores
where possible.

~Andrew

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