From: Stefano Garzarella <sgarzare@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: virtualization <virtualization@lists.linux-foundation.org>,
"Eugenio Pérez" <eperezma@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch
Date: Thu, 23 Jun 2022 10:58:30 +0200 [thread overview]
Message-ID: <20220623085830.voi6gixpikz64nm2@sgarzare-redhat> (raw)
In-Reply-To: <CACGkMEsk-O=dVwKoEHRY-nL3XEQktPWiBot2NfOUYNdkoL-s=Q@mail.gmail.com>
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@redhat.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@redhat.com>
>> Signed-off-by: Stefano Garzarella <sgarzare@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);
>> +
>
>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
WARNING: multiple messages have this Message-ID (diff)
From: Stefano Garzarella <sgarzare@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: "Eugenio Pérez" <eperezma@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
virtualization <virtualization@lists.linux-foundation.org>
Subject: Re: [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch
Date: Thu, 23 Jun 2022 10:58:30 +0200 [thread overview]
Message-ID: <20220623085830.voi6gixpikz64nm2@sgarzare-redhat> (raw)
In-Reply-To: <CACGkMEsk-O=dVwKoEHRY-nL3XEQktPWiBot2NfOUYNdkoL-s=Q@mail.gmail.com>
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@redhat.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@redhat.com>
>> Signed-off-by: Stefano Garzarella <sgarzare@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);
>> +
>
>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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next prev parent reply other threads:[~2022-06-23 8:58 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-21 16:08 [PATCH 0/3] vdpa_sim_blk: several fixes for the vDPA block simulator Stefano Garzarella
2022-06-21 16:08 ` Stefano Garzarella
2022-06-21 16:08 ` [PATCH 1/3] vdpa_sim_blk: use dev_dbg() to print errors Stefano Garzarella
2022-06-21 16:08 ` Stefano Garzarella
2022-06-23 3:40 ` Jason Wang
2022-06-23 3:40 ` Jason Wang
2022-06-21 16:08 ` [PATCH 2/3] vdpa_sim_blk: limit the number of request handled per batch Stefano Garzarella
2022-06-21 16:08 ` Stefano Garzarella
2022-06-23 3:50 ` Jason Wang
2022-06-23 3:50 ` Jason Wang
2022-06-23 8:58 ` Stefano Garzarella [this message]
2022-06-23 8:58 ` Stefano Garzarella
2022-06-28 4:01 ` Jason Wang
2022-06-28 4:01 ` Jason Wang
2022-06-28 7:55 ` Stefano Garzarella
2022-06-28 7:55 ` Stefano Garzarella
2022-06-21 16:12 ` [PATCH 3/3] vdpa_sim_blk: call vringh_complete_iotlb() also in the error path Stefano Garzarella
2022-06-21 16:12 ` Stefano Garzarella
2022-06-23 3:52 ` Jason Wang
2022-06-23 3:52 ` Jason Wang
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