Commit 6e77b0b6 authored by Darek Stojaczyk's avatar Darek Stojaczyk Committed by Jim Harris
Browse files

vhost: make poll group refcount per-session 



Change the way we increase poll group reference counts
for round-robin scheduling.

So far we used to increase them whenever someone called
vhost_get_poll_group() and this worked fine for Vhost-Block
which picks a new poll group for each session. Vhost-SCSI,
however, picks only one poll group for all sessions on
a vhost device. This means that some threads will have
multiple Vhost-SCSI pollers but will still appear to the
vhost scheduler as if they had only one.

To fix it, increase poll group refcnt only when sessions
are really being started - in vhost_session_start_done().

Change-Id: I60f0d2101239e5a91138a5afd30c51dc1ccf7c2e
Signed-off-by: default avatarDarek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/466733


Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: default avatarVitaliy Mysak <vitaliy.mysak@intel.com>
Reviewed-by: default avatarJim Harris <james.r.harris@intel.com>
Reviewed-by: default avatarChangpeng Liu <changpeng.liu@intel.com>
parent 1eba4323

lib/vhost/vhost.c

+9 −9
Original line number Diff line number Diff line
@@ -890,23 +890,18 @@ vhost_get_poll_group(struct spdk_cpuset *cpumask) 
	}



	assert(selected_pg != NULL);

	assert(selected_pg->ref < UINT_MAX);

	selected_pg->ref++;

	return selected_pg;

}



void

vhost_put_poll_group(struct vhost_poll_group *pg)

{

	assert(pg->ref > 0);

	pg->ref--;

}



void

vhost_session_start_done(struct spdk_vhost_session *vsession, int response)

{

	if (response == 0) {

		vsession->started = true;

		assert(vsession->poll_group != NULL);

		assert(vsession->poll_group->ref < UINT_MAX);

		vsession->poll_group->ref++;



		assert(vsession->vdev->active_session_num < UINT32_MAX);

		vsession->vdev->active_session_num++;

	}
@@ -920,6 +915,11 @@ vhost_session_stop_done(struct spdk_vhost_session *vsession, int response) 
{

	if (response == 0) {

		vsession->started = false;

		assert(vsession->poll_group != NULL);

		assert(vsession->poll_group->ref > 0);

		vsession->poll_group->ref--;

		vsession->poll_group = NULL;



		assert(vsession->vdev->active_session_num > 0);

		vsession->vdev->active_session_num--;

	}

lib/vhost/vhost_blk.c

+2 −9
Original line number Diff line number Diff line
@@ -712,17 +712,10 @@ static int 
vhost_blk_start(struct spdk_vhost_session *vsession)

{

	struct vhost_poll_group *pg;

	int rc;



	pg = vhost_get_poll_group(vsession->vdev->cpumask);

	rc = vhost_session_send_event(pg, vsession, vhost_blk_start_cb,

	return vhost_session_send_event(pg, vsession, vhost_blk_start_cb,

					3, "start session");



	if (rc != 0) {

		vhost_put_poll_group(pg);

	}



	return rc;

}



static int

lib/vhost/vhost_nvme.c

+2 −9
Original line number Diff line number Diff line
@@ -1114,7 +1114,6 @@ static int 
spdk_vhost_nvme_start(struct spdk_vhost_session *vsession)

{

	struct vhost_poll_group *pg;

	int rc;



	if (vsession->vdev->active_session_num > 0) {

		/* We're trying to start a second session */
@@ -1123,14 +1122,8 @@ spdk_vhost_nvme_start(struct spdk_vhost_session *vsession) 
	}



	pg = vhost_get_poll_group(vsession->vdev->cpumask);

	rc = vhost_session_send_event(pg, vsession, spdk_vhost_nvme_start_cb,

	return vhost_session_send_event(pg, vsession, spdk_vhost_nvme_start_cb,

					3, "start session");



	if (rc != 0) {

		vhost_put_poll_group(pg);

	}



	return rc;

}



static void

lib/vhost/vhost_scsi.c

+0 −2
Original line number Diff line number Diff line
@@ -1358,7 +1358,6 @@ vhost_scsi_start(struct spdk_vhost_session *vsession) 
				      3, "start session");

	if (rc != 0) {

		if (svdev->vdev.active_session_num == 0) {

			vhost_put_poll_group(svdev->poll_group);

			svdev->poll_group = NULL;

		}

	}
@@ -1459,7 +1458,6 @@ vhost_scsi_stop(struct spdk_vhost_session *vsession) 
	}



	if (vsession->vdev->active_session_num == 0) {

		vhost_put_poll_group(svsession->svdev->poll_group);

		svsession->svdev->poll_group = NULL;

	}

	return 0;