Il 30/07/2014 13:39, Ming Lei ha scritto: > g_slice_new(VirtIOBlockReq), its free pair and access the instance > is a bit slow since sizeof(VirtIOBlockReq) takes more than 40KB, > so use object pool to speed up its allocation and release. > > With this patch, ~5% throughput improvement is observed in the VM > based on server. > > Signed-off-by: Ming Lei <ming....@canonical.com> > --- > hw/block/dataplane/virtio-blk.c | 12 ++++++++++++ > hw/block/virtio-blk.c | 13 +++++++++++-- > include/hw/virtio/virtio-blk.h | 2 ++ > 3 files changed, 25 insertions(+), 2 deletions(-) > > diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c > index 2093e4a..828fe99 100644 > --- a/hw/block/dataplane/virtio-blk.c > +++ b/hw/block/dataplane/virtio-blk.c > @@ -24,6 +24,8 @@ > #include "hw/virtio/virtio-bus.h" > #include "qom/object_interfaces.h" > > +#define REQ_POOL_SZ 128 > + > struct VirtIOBlockDataPlane { > bool started; > bool starting; > @@ -51,6 +53,10 @@ struct VirtIOBlockDataPlane { > Error *blocker; > void (*saved_complete_request)(struct VirtIOBlockReq *req, > unsigned char status); > + > + VirtIOBlockReq reqs[REQ_POOL_SZ]; > + void *free_reqs[REQ_POOL_SZ]; > + ObjPool req_pool; > }; > > /* Raise an interrupt to signal guest, if necessary */ > @@ -238,6 +244,10 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s) > return; > } > > + vblk->obj_pool = &s->req_pool; > + obj_pool_init(vblk->obj_pool, s->reqs, s->free_reqs, > + sizeof(VirtIOBlockReq), REQ_POOL_SZ); > + > /* Set up guest notifier (irq) */ > if (k->set_guest_notifiers(qbus->parent, 1, true) != 0) { > fprintf(stderr, "virtio-blk failed to set guest notifier, " > @@ -298,6 +308,8 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s) > > aio_context_release(s->ctx); > > + vblk->obj_pool = NULL; > + > if (s->raw_format) { > qemu_aio_set_bypass_co(s->ctx, false); > } > diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c > index c241c50..2a11bc4 100644 > --- a/hw/block/virtio-blk.c > +++ b/hw/block/virtio-blk.c > @@ -31,7 +31,11 @@ > > VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s) > { > - VirtIOBlockReq *req = g_slice_new(VirtIOBlockReq); > + VirtIOBlockReq *req = obj_pool_get(s->obj_pool); > + > + if (!req) { > + req = g_slice_new(VirtIOBlockReq); > + } > req->dev = s; > req->qiov.size = 0; > req->next = NULL; > @@ -41,7 +45,11 @@ VirtIOBlockReq *virtio_blk_alloc_request(VirtIOBlock *s) > void virtio_blk_free_request(VirtIOBlockReq *req) > { > if (req) { > - g_slice_free(VirtIOBlockReq, req); > + if (obj_pool_has_obj(req->dev->obj_pool, req)) { > + obj_pool_put(req->dev->obj_pool, req); > + } else { > + g_slice_free(VirtIOBlockReq, req); > + } > } > } > > @@ -801,6 +809,7 @@ static void virtio_blk_instance_init(Object *obj) > { > VirtIOBlock *s = VIRTIO_BLK(obj); > > + s->obj_pool = NULL; > object_property_add_link(obj, "iothread", TYPE_IOTHREAD, > (Object **)&s->blk.iothread, > qdev_prop_allow_set_link_before_realize, > diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h > index afb7b8d..49ac234 100644 > --- a/include/hw/virtio/virtio-blk.h > +++ b/include/hw/virtio/virtio-blk.h > @@ -18,6 +18,7 @@ > #include "hw/block/block.h" > #include "sysemu/iothread.h" > #include "block/block.h" > +#include "qemu/obj_pool.h" > > #define TYPE_VIRTIO_BLK "virtio-blk-device" > #define VIRTIO_BLK(obj) \ > @@ -135,6 +136,7 @@ typedef struct VirtIOBlock { > Notifier migration_state_notifier; > struct VirtIOBlockDataPlane *dataplane; > #endif > + ObjPool *obj_pool; > } VirtIOBlock; > > typedef struct MultiReqBuffer { >
The problem is that g_slice here is not using the slab-style allocator because the object is larger than roughly 500 bytes. One solution would be to make virtqueue_pop/vring_pop allocate a VirtQueueElement of the right size (and virtqueue_push/vring_push free it), as mentioned in the review of patch 8. However, I now remembered that VirtQueueElement is a mess because it's serialized directly into the migration state. :( So you basically cannot change it without mucking with migration. Please leave out patch 8 for now. Let's use this object pool, however, please simplify the API, it should be just: void obj_pool_init(ObjPool *pool, unsigned obj_size, unsigned cnt); void *obj_pool_alloc(ObjPool *pool); void obj_pool_free(ObjPool *pool, void *obj); void obj_pool_destroy(ObjPool *pool); All allocations of the objs buffer, and all logic like + VirtIOBlockReq *req = obj_pool_get(s->obj_pool); + + if (!req) { + req = g_slice_new(VirtIOBlockReq); + } + if (obj_pool_has_obj(req->dev->obj_pool, req)) { + obj_pool_put(req->dev->obj_pool, req); + } else { + g_slice_free(VirtIOBlockReq, req); + } should be part of the object pool, not its users. Paolo