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Date: Tue, 28 Jun 2022 12:01:02 +0800 From: Jason Wang <jasowang@...hat.com> To: Stefano Garzarella <sgarzare@...hat.com> Cc: virtualization <virtualization@...ts.linux-foundation.org>, Eugenio Pérez <eperezma@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, linux-kernel <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch On Thu, Jun 23, 2022 at 4:58 PM Stefano Garzarella <sgarzare@...hat.com> wrote: > > On Thu, Jun 23, 2022 at 11:50:22AM +0800, Jason Wang wrote: > >On Wed, Jun 22, 2022 at 12:09 AM Stefano Garzarella <sgarzare@...hat.com> wrote: > >> > >> 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 <eperezma@...hat.com> > >> Signed-off-by: Stefano Garzarella <sgarzare@...hat.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); > >> + > > > >Is it better to check and exit the loop early here? > > Maybe, but I'm not sure. > > In vdpa_sim_net we call vringh_complete_iotlb() and send notification > also in the error path, Looks not? read = vringh_iov_pull_iotlb(&cvq->vring, &cvq->in_iov, &ctrl, sizeof(ctrl)); if (read != sizeof(ctrl)) break; We break the loop. Thanks > so I thought was better to send notification > also when vdpasim_blk_handle_req() return false, since we will update > the used.idx. > > However, I don't think it's a common path, so if you think it's better > to exit the loop early, I can do it. > > Thanks, > Stefano >
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