similar to: [RFC v2 0/2] virtio: Support releasing lock during kick

The virtio block device holds a lock during I/O request processing. Kicking the virtqueue while the lock is held results in long lock hold times and increases contention for the lock. This patch modifies virtqueue_kick() to optionally release a lock while notifying the host. Virtio block is modified to pass in its lock. This allows other vcpus to queue I/O requests during the time spent

The virtio block device holds a lock during I/O request processing. Kicking the virtqueue while the lock is held results in long lock hold times and increases contention for the lock. This patch modifies virtqueue_kick() to optionally release a lock while notifying the host. Virtio block is modified to pass in its lock. This allows other vcpus to queue I/O requests during the time spent

virtqueue ops were introduced in the hope that we'll have multiple implementations besides virtio_ring, but none have surfaced so far, and given that existing virtio ring is deployed in production we are likely stuck with it now, so this layer just adds complexity and overhead. Further, the need to pass vq twice to each call (as in dev->vq->vq_ops->kick(dev->vq) ) adds potential

virtqueue ops were introduced in the hope that we'll have multiple implementations besides virtio_ring, but none have surfaced so far, and given that existing virtio ring is deployed in production we are likely stuck with it now, so this layer just adds complexity and overhead. Further, the need to pass vq twice to each call (as in dev->vq->vq_ops->kick(dev->vq) ) adds potential

Add virtqueue_add_sgs which is more general than virtqueue_add_buf, which makes virtio-scsi and virtio-blk nicer, then add virtqueue_add_inbuf and virtqueue_add_outbuf which handle the more general case, and finally delete virtqueue_add_buf(). I'm hoping this will be the final post of the whole series, and it can move from my pending-rebases tree into virtio-next. Thanks! Rusty. Paolo

Add virtqueue_add_sgs which is more general than virtqueue_add_buf, which makes virtio-scsi and virtio-blk nicer, then add virtqueue_add_inbuf and virtqueue_add_outbuf which handle the more general case, and finally delete virtqueue_add_buf(). I'm hoping this will be the final post of the whole series, and it can move from my pending-rebases tree into virtio-next. Thanks! Rusty. Paolo

OK, this is (ab)uses some of Paolo's patches. The first 7 are candidates for this merge window (maybe), the rest I'm not so sure about. Thanks, Rusty. Paolo Bonzini (3): scatterlist: introduce sg_unmark_end virtio-blk: reorganize virtblk_add_req virtio-blk: use virtqueue_add_sgs on req path Rusty Russell (13): virtio_ring: virtqueue_add_sgs, to add multiple sgs. virtio-blk:

OK, this is (ab)uses some of Paolo's patches. The first 7 are candidates for this merge window (maybe), the rest I'm not so sure about. Thanks, Rusty. Paolo Bonzini (3): scatterlist: introduce sg_unmark_end virtio-blk: reorganize virtblk_add_req virtio-blk: use virtqueue_add_sgs on req path Rusty Russell (13): virtio_ring: virtqueue_add_sgs, to add multiple sgs. virtio-blk:

Holding the vblk->lock across kick causes poor scalability in SMP guests. If one CPU is doing virtqueue kick and another CPU touches the vblk->lock it will have to spin until virtqueue kick completes. This patch reduces system% CPU utilization in SMP guests that are running multithreaded I/O-bound workloads. The improvements are small but show as iops and SMP are increased. Khoa Huynh

Holding the vblk->lock across kick causes poor scalability in SMP guests. If one CPU is doing virtqueue kick and another CPU touches the vblk->lock it will have to spin until virtqueue kick completes. This patch reduces system% CPU utilization in SMP guests that are running multithreaded I/O-bound workloads. The improvements are small but show as iops and SMP are increased. Khoa Huynh

Most device drivers do not need to perform any postprocessing on the scatterlists they receive from higher-level drivers (e.g. the block or SCSI layer), because they translate the request metadata directly from the various C structs into the data that is required by the device. virtio devices however do this translation in two steps: a device-specific step in the device driver, and generic

Most device drivers do not need to perform any postprocessing on the scatterlists they receive from higher-level drivers (e.g. the block or SCSI layer), because they translate the request metadata directly from the various C structs into the data that is required by the device. virtio devices however do this translation in two steps: a device-specific step in the device driver, and generic

Hi, These patches try to support multi virtual queues(multi-vq) in one virtio-blk device, and maps each virtual queue(vq) to blk-mq's hardware queue. With this approach, both scalability and performance on virtio-blk device can get improved. For verifying the improvement, I implements virtio-blk multi-vq over qemu's dataplane feature, and both handling host notification from each vq and

Hi, These patches try to support multi virtual queues(multi-vq) in one virtio-blk device, and maps each virtual queue(vq) to blk-mq's hardware queue. With this approach, both scalability and performance on virtio-blk device can get improved. For verifying the improvement, I implements virtio-blk multi-vq over qemu's dataplane feature, and both handling host notification from each vq and

Hi, These patches try to support multi virtual queues(multi-vq) in one virtio-blk device, and maps each virtual queue(vq) to blk-mq's hardware queue. With this approach, both scalability and performance on virtio-blk device can get improved. For verifying the improvement, I implements virtio-blk multi-vq over qemu's dataplane feature, and both handling host notification from each vq and

Hi, These patches try to support multi virtual queues(multi-vq) in one virtio-blk device, and maps each virtual queue(vq) to blk-mq's hardware queue. With this approach, both scalability and performance on virtio-blk device can get improved. For verifying the improvement, I implements virtio-blk multi-vq over qemu's dataplane feature, and both handling host notification from each vq and

Hi, These patches try to support multi virtual queues(multi-vq) in one virtio-blk device, and maps each virtual queue(vq) to blk-mq's hardware queue. With this approach, both scalability and performance on virtio-blk device can get improved. For verifying the improvement, I implements virtio-blk multi-vq over qemu's dataplane feature, and both handling host notification from each vq and

Hi, These patches try to support multi virtual queues(multi-vq) in one virtio-blk device, and maps each virtual queue(vq) to blk-mq's hardware queue. With this approach, both scalability and performance on virtio-blk device can get improved. For verifying the improvement, I implements virtio-blk multi-vq over qemu's dataplane feature, and both handling host notification from each vq and

This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h | 5 +++++ 2 files changed, 13

This helper returns 1 if a call to add_buf will not fail with -ENOSPC. This will help callers that do while(1) { alloc() if (add_buf()) { free(); break; } } This will result in one less alloc/free exercise. Signed-off-by: Amit Shah <amit.shah at redhat.com> --- drivers/virtio/virtio_ring.c | 8 ++++++++ include/linux/virtio.h | 5 +++++ 2 files changed, 13