[PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch

[Stefano Garzarella]

Limit the number of requests (4 per queue as for vdpa_sim_net) handled
in a batch to prevent the worker from using the CPU for too long.

Suggested-by: Eugenio Pérez <epere...@redhat.com>
Signed-off-by: Stefano Garzarella <sgarz...@redhat.com>
---
 drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c 
b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
index a83a5c76f620..ac86478845b6 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
@@ -197,6 +197,7 @@ static bool vdpasim_blk_handle_req(struct vdpasim *vdpasim,
 static void vdpasim_blk_work(struct work_struct *work)
 {
        struct vdpasim *vdpasim = container_of(work, struct vdpasim, work);
+       bool reschedule = false;
        int i;
 
        spin_lock(&vdpasim->lock);
@@ -206,11 +207,15 @@ static void vdpasim_blk_work(struct work_struct *work)
 
        for (i = 0; i < VDPASIM_BLK_VQ_NUM; i++) {
                struct vdpasim_virtqueue *vq = &vdpasim->vqs[i];
+               bool vq_work = true;
+               int reqs = 0;
 
                if (!vq->ready)
                        continue;
 
-               while (vdpasim_blk_handle_req(vdpasim, vq)) {
+               while (vq_work) {
+                       vq_work = vdpasim_blk_handle_req(vdpasim, vq);
+
                        /* Make sure used is visible before rasing the 
interrupt. */
                        smp_wmb();
 
@@ -218,10 +223,18 @@ static void vdpasim_blk_work(struct work_struct *work)
                        if (vringh_need_notify_iotlb(&vq->vring) > 0)
                                vringh_notify(&vq->vring);
                        local_bh_enable();
+
+                       if (++reqs > 4) {
+                               vq_work = false;
+                               reschedule = true;
+                       }
                }
        }
 out:
        spin_unlock(&vdpasim->lock);
+
+       if (reschedule)
+               schedule_work(&vdpasim->work);
 }
 
 static void vdpasim_blk_get_config(struct vdpasim *vdpasim, void *config)
-- 
2.36.1

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