From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 80AEDC433F5 for ; Fri, 7 Sep 2018 14:10:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1EAB120869 for ; Fri, 7 Sep 2018 14:10:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1EAB120869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728969AbeIGSv2 (ORCPT ); Fri, 7 Sep 2018 14:51:28 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:54744 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726594AbeIGSv2 (ORCPT ); Fri, 7 Sep 2018 14:51:28 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id ABA5A40216FC; Fri, 7 Sep 2018 14:10:19 +0000 (UTC) Received: from redhat.com (ovpn-124-199.rdu2.redhat.com [10.10.124.199]) by smtp.corp.redhat.com (Postfix) with SMTP id 988562027EA0; Fri, 7 Sep 2018 14:10:15 +0000 (UTC) Date: Fri, 7 Sep 2018 10:10:14 -0400 From: "Michael S. Tsirkin" To: Tiwei Bie Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtio-dev@lists.oasis-open.org, wexu@redhat.com, jfreimann@redhat.com Subject: Re: [PATCH net-next v2 4/5] virtio_ring: add event idx support in packed ring Message-ID: <20180907100341-mutt-send-email-mst@kernel.org> References: <20180711022711.7090-1-tiwei.bie@intel.com> <20180711022711.7090-5-tiwei.bie@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180711022711.7090-5-tiwei.bie@intel.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Fri, 07 Sep 2018 14:10:19 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Fri, 07 Sep 2018 14:10:19 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 11, 2018 at 10:27:10AM +0800, Tiwei Bie wrote: > This commit introduces the EVENT_IDX support in packed ring. > > Signed-off-by: Tiwei Bie Besides the usual comment about hard-coded constants like <<15: does this actually do any good for performance? We don't have to if we do not want to. > --- > drivers/virtio/virtio_ring.c | 73 ++++++++++++++++++++++++++++++++---- > 1 file changed, 65 insertions(+), 8 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index f317b485ba54..f79a1e17f7d1 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -1050,7 +1050,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > - u16 flags; > + u16 new, old, off_wrap, flags, wrap_counter, event_idx; > bool needs_kick; > u32 snapshot; > > @@ -1059,9 +1059,19 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > * suppressions. */ > virtio_mb(vq->weak_barriers); > > + old = vq->next_avail_idx - vq->num_added; > + new = vq->next_avail_idx; > + vq->num_added = 0; > + > snapshot = READ_ONCE(*(u32 *)vq->vring_packed.device); > + off_wrap = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot & 0xffff)); > flags = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot >> 16)) & 0x3; some kind of struct union would be helpful to make this readable. > > + wrap_counter = off_wrap >> 15; > + event_idx = off_wrap & ~(1 << 15); > + if (wrap_counter != vq->avail_wrap_counter) > + event_idx -= vq->vring_packed.num; > + > #ifdef DEBUG > if (vq->last_add_time_valid) { > WARN_ON(ktime_to_ms(ktime_sub(ktime_get(), > @@ -1070,7 +1080,10 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > vq->last_add_time_valid = false; > #endif > > - needs_kick = (flags != VRING_EVENT_F_DISABLE); > + if (flags == VRING_EVENT_F_DESC) > + needs_kick = vring_need_event(event_idx, new, old); > + else > + needs_kick = (flags != VRING_EVENT_F_DISABLE); > END_USE(vq); > return needs_kick; > } > @@ -1185,6 +1198,15 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > ret = vq->desc_state_packed[id].data; > detach_buf_packed(vq, id, ctx); > > + /* If we expect an interrupt for the next entry, tell host > + * by writing event index and flush out the write before > + * the read in the next get_buf call. */ > + if (vq->event_flags_shadow == VRING_EVENT_F_DESC) > + virtio_store_mb(vq->weak_barriers, > + &vq->vring_packed.driver->off_wrap, > + cpu_to_virtio16(_vq->vdev, vq->last_used_idx | > + ((u16)vq->used_wrap_counter << 15))); > + > #ifdef DEBUG > vq->last_add_time_valid = false; > #endif > @@ -1213,8 +1235,18 @@ static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq) > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > > + if (vq->event) { > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + vq->last_used_idx | > + ((u16)vq->used_wrap_counter << 15)); > + /* We need to update event offset and event wrap > + * counter first before updating event flags. */ > + virtio_wmb(vq->weak_barriers); > + } > + > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > } > @@ -1238,22 +1270,47 @@ static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned off_wrap) > static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > + u16 bufs, used_idx, wrap_counter; > > START_USE(vq); > > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > > + if (vq->event) { > + /* TODO: tune this threshold */ > + bufs = (vq->vring_packed.num - _vq->num_free) * 3 / 4; > + wrap_counter = vq->used_wrap_counter; > + > + used_idx = vq->last_used_idx + bufs; > + if (used_idx >= vq->vring_packed.num) { > + used_idx -= vq->vring_packed.num; > + wrap_counter ^= 1; > + } > + > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + used_idx | (wrap_counter << 15)); > + > + /* We need to update event offset and event wrap > + * counter first before updating event flags. */ > + virtio_wmb(vq->weak_barriers); > + } else { > + used_idx = vq->last_used_idx; > + wrap_counter = vq->used_wrap_counter; > + } > + > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > - /* We need to enable interrupts first before re-checking > - * for more used buffers. */ > - virtio_mb(vq->weak_barriers); > } > > - if (more_used_packed(vq)) { > + /* We need to update event suppression structure first > + * before re-checking for more used buffers. */ > + virtio_mb(vq->weak_barriers); > + mb is expensive. We should not do it if we changed nothing. > + if (is_used_desc_packed(vq, used_idx, wrap_counter)) { > END_USE(vq); > return false; > } > -- > 2.18.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-4821-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 1F0A3985F36 for ; Fri, 7 Sep 2018 14:10:21 +0000 (UTC) Date: Fri, 7 Sep 2018 10:10:14 -0400 From: "Michael S. Tsirkin" Message-ID: <20180907100341-mutt-send-email-mst@kernel.org> References: <20180711022711.7090-1-tiwei.bie@intel.com> <20180711022711.7090-5-tiwei.bie@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180711022711.7090-5-tiwei.bie@intel.com> Subject: [virtio-dev] Re: [PATCH net-next v2 4/5] virtio_ring: add event idx support in packed ring To: Tiwei Bie Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, virtio-dev@lists.oasis-open.org, wexu@redhat.com, jfreimann@redhat.com List-ID: On Wed, Jul 11, 2018 at 10:27:10AM +0800, Tiwei Bie wrote: > This commit introduces the EVENT_IDX support in packed ring. > > Signed-off-by: Tiwei Bie Besides the usual comment about hard-coded constants like <<15: does this actually do any good for performance? We don't have to if we do not want to. > --- > drivers/virtio/virtio_ring.c | 73 ++++++++++++++++++++++++++++++++---- > 1 file changed, 65 insertions(+), 8 deletions(-) > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index f317b485ba54..f79a1e17f7d1 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -1050,7 +1050,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, > static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > - u16 flags; > + u16 new, old, off_wrap, flags, wrap_counter, event_idx; > bool needs_kick; > u32 snapshot; > > @@ -1059,9 +1059,19 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > * suppressions. */ > virtio_mb(vq->weak_barriers); > > + old = vq->next_avail_idx - vq->num_added; > + new = vq->next_avail_idx; > + vq->num_added = 0; > + > snapshot = READ_ONCE(*(u32 *)vq->vring_packed.device); > + off_wrap = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot & 0xffff)); > flags = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot >> 16)) & 0x3; some kind of struct union would be helpful to make this readable. > > + wrap_counter = off_wrap >> 15; > + event_idx = off_wrap & ~(1 << 15); > + if (wrap_counter != vq->avail_wrap_counter) > + event_idx -= vq->vring_packed.num; > + > #ifdef DEBUG > if (vq->last_add_time_valid) { > WARN_ON(ktime_to_ms(ktime_sub(ktime_get(), > @@ -1070,7 +1080,10 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) > vq->last_add_time_valid = false; > #endif > > - needs_kick = (flags != VRING_EVENT_F_DISABLE); > + if (flags == VRING_EVENT_F_DESC) > + needs_kick = vring_need_event(event_idx, new, old); > + else > + needs_kick = (flags != VRING_EVENT_F_DISABLE); > END_USE(vq); > return needs_kick; > } > @@ -1185,6 +1198,15 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, > ret = vq->desc_state_packed[id].data; > detach_buf_packed(vq, id, ctx); > > + /* If we expect an interrupt for the next entry, tell host > + * by writing event index and flush out the write before > + * the read in the next get_buf call. */ > + if (vq->event_flags_shadow == VRING_EVENT_F_DESC) > + virtio_store_mb(vq->weak_barriers, > + &vq->vring_packed.driver->off_wrap, > + cpu_to_virtio16(_vq->vdev, vq->last_used_idx | > + ((u16)vq->used_wrap_counter << 15))); > + > #ifdef DEBUG > vq->last_add_time_valid = false; > #endif > @@ -1213,8 +1235,18 @@ static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq) > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > > + if (vq->event) { > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + vq->last_used_idx | > + ((u16)vq->used_wrap_counter << 15)); > + /* We need to update event offset and event wrap > + * counter first before updating event flags. */ > + virtio_wmb(vq->weak_barriers); > + } > + > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > } > @@ -1238,22 +1270,47 @@ static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned off_wrap) > static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq) > { > struct vring_virtqueue *vq = to_vvq(_vq); > + u16 bufs, used_idx, wrap_counter; > > START_USE(vq); > > /* We optimistically turn back on interrupts, then check if there was > * more to do. */ > > + if (vq->event) { > + /* TODO: tune this threshold */ > + bufs = (vq->vring_packed.num - _vq->num_free) * 3 / 4; > + wrap_counter = vq->used_wrap_counter; > + > + used_idx = vq->last_used_idx + bufs; > + if (used_idx >= vq->vring_packed.num) { > + used_idx -= vq->vring_packed.num; > + wrap_counter ^= 1; > + } > + > + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, > + used_idx | (wrap_counter << 15)); > + > + /* We need to update event offset and event wrap > + * counter first before updating event flags. */ > + virtio_wmb(vq->weak_barriers); > + } else { > + used_idx = vq->last_used_idx; > + wrap_counter = vq->used_wrap_counter; > + } > + > if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { > - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; > + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : > + VRING_EVENT_F_ENABLE; > vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, > vq->event_flags_shadow); > - /* We need to enable interrupts first before re-checking > - * for more used buffers. */ > - virtio_mb(vq->weak_barriers); > } > > - if (more_used_packed(vq)) { > + /* We need to update event suppression structure first > + * before re-checking for more used buffers. */ > + virtio_mb(vq->weak_barriers); > + mb is expensive. We should not do it if we changed nothing. > + if (is_used_desc_packed(vq, used_idx, wrap_counter)) { > END_USE(vq); > return false; > } > -- > 2.18.0 --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org