Re: [Xen-devel] [PATCH RFC 09/12] xen-blkback: move pendinghandles list from blkbk to pending_req

From: Jan Beulich
Date: Thu Feb 28 2013 - 06:07:32 EST

>>> On 28.02.13 at 11:28, Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> Moving grant ref handles from blkbk to pending_req will allow us to
> get rid of the shared blkbk structure.

At the expense of (slightly?) higher memory requirements?

> --- a/drivers/block/xen-blkback/blkback.c
> +++ b/drivers/block/xen-blkback/blkback.c
> @@ -136,6 +136,7 @@ struct pending_req {
> struct list_head free_list;
> struct persistent_gnt *persistent_gnts[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> struct page *pages[BLKIF_MAX_SEGMENTS_PER_REQUEST];
> + grant_handle_t grant_handles[BLKIF_MAX_SEGMENTS_PER_REQUEST];

Adding yet another array here makes it even more desirable to
switch from multiple arrays to a singly array of a structure, thus
improving locality of the memory accesses involved in processing
an individual segment.


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