Re: [Xen-devel] [RFC PATCH V4 11/18] Bump EVTCHNS_PER_BUCKET to 512

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 05/03/13 12:30, Wei Liu wrote:
> For 64 bit build and 3-level event channel and the original value of
> EVTCHNS_PER_BUCKET (128), the space needed to accommodate d->evtchn would be 4
> pages (PAGE_SIZE = 4096). Given that not every domain needs 3-level event
> channel, this leads to waste of memory. Having EVTCHN_PER_BUCKETS to be 512
> can occupy exact one page.

This makes the list of buckets a page in size but each bucket is now 4
pages.

I think another layer of indirection is required to keep all the
allocations <= PAGE_SIZE.

David

> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  xen/include/xen/event.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/include/xen/event.h b/xen/include/xen/event.h
> index 919f0e2..e2c3736 100644
> --- a/xen/include/xen/event.h
> +++ b/xen/include/xen/event.h
> @@ -39,7 +39,7 @@ static inline unsigned int max_evtchns(struct domain *d)
>      return ret;
>  }
>  
> -#define EVTCHNS_PER_BUCKET 128
> +#define EVTCHNS_PER_BUCKET 512
>  #define NR_EVTCHN_BUCKETS  (NR_EVENT_CHANNELS / EVTCHNS_PER_BUCKET)
>  
>  struct evtchn


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