Re: [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch
On Tue, Jun 28, 2022 at 6:01 AM Jason Wang wrote:
>
> On Thu, Jun 23, 2022 at 4:58 PM Stefano Garzarella
> 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
> > >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
> > >> Signed-off-by: Stefano Garzarella
> > >> ---
> > >> 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.
I was looking at vdpasim_net_work(), but I was confused since it
handles 2 queues.
I'll break the loop as it was before.
Thanks,
Stefano
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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 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
> >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
> >> Signed-off-by: Stefano Garzarella
> >> ---
> >> 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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Re: [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch
On Thu, Jun 23, 2022 at 11:50:22AM +0800, Jason Wang wrote:
On Wed, Jun 22, 2022 at 12:09 AM Stefano Garzarella 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
Signed-off-by: Stefano Garzarella
---
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, 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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Re: [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch
On Wed, Jun 22, 2022 at 12:09 AM Stefano Garzarella 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
> Signed-off-by: Stefano Garzarella
> ---
> 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?
Thanks
> /* 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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