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virtio_ring: virtqueue_add_sgs, to add multiple sgs.

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virtio_scsi can really use this, to avoid the current hack of copying
the whole sg array.  Some other things get slightly neater, too.

This causes a slowdown in virtqueue_add_buf(), which is implemented as
a wrapper.  This is addressed in the next patches.

for i in `seq 50`; do /usr/bin/time -f 'Wall time:%e' ./vringh_test --indirect --eventidx --parallel --fast-vringh; done 2>&1 | stats --trim-outliers:

Before:
	Using CPUS 0 and 3
	Guest: notified 0, pinged 39009-39063(39062)
	Host: notified 39009-39063(39062), pinged 0
	Wall time:1.700000-1.950000(1.723542)

After:
	Using CPUS 0 and 3
	Guest: notified 0, pinged 39062-39063(39063)
	Host: notified 39062-39063(39063), pinged 0
	Wall time:1.760000-2.220000(1.789167)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Reviewed-by: Asias He <asias@redhat.com>
This commit is contained in:
Rusty Russell 2013-03-20 15:37:09 +10:30
parent c8164d8931
commit 13816c768d
4 changed files with 186 additions and 62 deletions
Download patch file Download diff file Expand all files Collapse all files

16
tools/virtio/linux/scatterlist.h
View file

@ -125,6 +125,22 @@ static inline void sg_mark_end(struct scatterlist *sg)
sg->page_link &= ~0x01;
}
/**
* sg_unmark_end - Undo setting the end of the scatterlist
* @sg: SG entryScatterlist
*
* Description:
* Removes the termination marker from the given entry of the scatterlist.
*
**/
static inline void sg_unmark_end(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG
BUG_ON(sg->sg_magic != SG_MAGIC);
#endif
sg->page_link &= ~0x02;
}
static inline struct scatterlist *sg_next(struct scatterlist *sg)
{
#ifdef CONFIG_DEBUG_SG

7
tools/virtio/linux/virtio.h
View file

@ -56,6 +56,13 @@ int virtqueue_add_buf(struct virtqueue *vq,
void *data,
gfp_t gfp);
int virtqueue_add_sgs(struct virtqueue *vq,
struct scatterlist *sgs[],
unsigned int out_sgs,
unsigned int in_sgs,
void *data,
gfp_t gfp);
void virtqueue_kick(struct virtqueue *vq);
void *virtqueue_get_buf(struct virtqueue *vq, unsigned int *len);