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Re: [Xen-devel] [PATCH v2 13/20] xen/events: fifo: Make it running on 64KB granularity

Hi David,

On 24/07/15 11:36, David Vrabel wrote:
> On 09/07/15 21:42, Julien Grall wrote:
>> Only use the first 4KB of the page to store the events channel info. It
>> means that we will wast 60KB every time we allocate page for:
>>      * control block: a page is allocating per CPU
>>      * event array: a page is allocating everytime we need to expand it
> Reviewed-by: David Vrabel <david.vrabel@xxxxxxxxxx>

Thank you!

>> I think we can reduce the memory waste for the 2 areas by:
>>     * control block: sharing between multiple vCPUs. Although it will
>>     require some bookkeeping in order to not free the page when the CPU
>>     goes offline and the other CPUs sharing the page still there
>>     * event array: always extend the array event by 64K (i.e 16 4K
>>     chunk). That would require more care when we fail to expand the
>>     event channel.
> I would extend it by 4 KiB each time but only allocate a new page every
> 16 times.  This minimizes the resources used in Xen.

I will keep it in mind when I will send a patch to reduce memory waster.


Julien Grall

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