Messages in this thread | | | Date | Wed, 19 Sep 2012 13:03:52 +0100 | From | "Jan Beulich" <> | Subject | Re: [Xen-devel] [PATCH] Persistent grant maps for xen blk drivers |
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>>> On 19.09.12 at 12:51, Oliver Chick <oliver.chick@citrix.com> wrote: > +/* > + * Maximum number of persistent grants that can be mapped by Dom0 for each > + * interface. This is set to be the size of the ring, as this is a limit on > + * the number of requests that can be inflight at any one time. 256 imposes > + * an overhead of 11MB of mapped kernel space per interface. > + */ > +#define BLKIF_MAX_PERS_REQUESTS_PER_DEV 256
How can this be a fixed number, especially in the context of ring size extensions? Iirc, single page rings can accommodate 64 requests, so I'd guess the number above was observed with a 4-page (order 2) ring...
Jan
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