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vhost-scsi: Reduce mem use by moving upages to per queue

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Each worker thread can process 1 command at a time so there's no need to
allocate a upages array per cmd. This patch moves it to per queue. Even a
small device with 128 cmds and 1 queue this brings mem use for the array
from

2 MB = 8 bytes per page pointer * 2048 pointers * 128 cmds

to

16K = 8 bytes per pointer * 2048 * 1 queue

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20241203191705.19431-2-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Mike Christie 2024-12-03 13:15:08 -06:00 committed by Michael S. Tsirkin
parent fc80842a27
commit 4c1f3a7d74
1 changed files with 10 additions and 14 deletions
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24
drivers/vhost/scsi.c
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@ -83,7 +83,6 @@ struct vhost_scsi_cmd {
/* Pointer to the SGL formatted memory from virtio-scsi */
struct scatterlist *tvc_sgl;
struct scatterlist *tvc_prot_sgl;
struct page **tvc_upages;
/* Pointer to response header iovec */
struct iovec *tvc_resp_iov;
/* Pointer to vhost_scsi for our device */
@ -187,6 +186,7 @@ struct vhost_scsi_virtqueue {
struct vhost_scsi_cmd *scsi_cmds;
struct sbitmap scsi_tags;
int max_cmds;
struct page **upages;
struct vhost_work completion_work;
struct llist_head completion_list;
@ -619,7 +619,6 @@ vhost_scsi_get_cmd(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
struct vhost_scsi_nexus *tv_nexus;
struct scatterlist *sg, *prot_sg;
struct iovec *tvc_resp_iov;
struct page **pages;
int tag;
tv_nexus = tpg->tpg_nexus;
@ -637,12 +636,10 @@ vhost_scsi_get_cmd(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
cmd = &svq->scsi_cmds[tag];
sg = cmd->tvc_sgl;
prot_sg = cmd->tvc_prot_sgl;
pages = cmd->tvc_upages;
tvc_resp_iov = cmd->tvc_resp_iov;
memset(cmd, 0, sizeof(*cmd));
cmd->tvc_sgl = sg;
cmd->tvc_prot_sgl = prot_sg;
cmd->tvc_upages = pages;
cmd->tvc_se_cmd.map_tag = tag;
cmd->tvc_tag = scsi_tag;
cmd->tvc_lun = lun;
@ -669,7 +666,9 @@ vhost_scsi_map_to_sgl(struct vhost_scsi_cmd *cmd,
struct scatterlist *sgl,
bool is_prot)
{
struct page **pages = cmd->tvc_upages;
struct vhost_scsi_virtqueue *svq = container_of(cmd->tvc_vq,
struct vhost_scsi_virtqueue, vq);
struct page **pages = svq->upages;
struct scatterlist *sg = sgl;
ssize_t bytes, mapped_bytes;
size_t offset, mapped_offset;
@ -1598,11 +1597,11 @@ static void vhost_scsi_destroy_vq_cmds(struct vhost_virtqueue *vq)
kfree(tv_cmd->tvc_sgl);
kfree(tv_cmd->tvc_prot_sgl);
kfree(tv_cmd->tvc_upages);
kfree(tv_cmd->tvc_resp_iov);
}
sbitmap_free(&svq->scsi_tags);
kfree(svq->upages);
kfree(svq->scsi_cmds);
svq->scsi_cmds = NULL;
}
@ -1628,6 +1627,11 @@ static int vhost_scsi_setup_vq_cmds(struct vhost_virtqueue *vq, int max_cmds)
return -ENOMEM;
}
svq->upages = kcalloc(VHOST_SCSI_PREALLOC_UPAGES, sizeof(struct page *),
GFP_KERNEL);
if (!svq->upages)
goto out;
for (i = 0; i < max_cmds; i++) {
tv_cmd = &svq->scsi_cmds[i];
@ -1639,14 +1643,6 @@ static int vhost_scsi_setup_vq_cmds(struct vhost_virtqueue *vq, int max_cmds)
goto out;
}
tv_cmd->tvc_upages = kcalloc(VHOST_SCSI_PREALLOC_UPAGES,
sizeof(struct page *),
GFP_KERNEL);
if (!tv_cmd->tvc_upages) {
pr_err("Unable to allocate tv_cmd->tvc_upages\n");
goto out;
}
tv_cmd->tvc_resp_iov = kcalloc(UIO_MAXIOV,
sizeof(struct iovec),
GFP_KERNEL);