this series adds the long missing multiread support to virtio-blk.
some remarks:
- i introduced rd_merged and wr_merged block accounting stats to
blockstats as a generic interface which can be set from any
driver that will introduce multirequest merging in the future.
- the knob to disable request merging is not yet there. I would
add it to the device properties also as a generic interface
to have the same switch for any driver that might introduce
request merging in the future. As there has been no knob in
the past I would post this as a seperate series as it needs
some mangling in parameter parsing which might lead to further
discussions.
- the old multiwrite interface is still there and might be removed.
v2->v3:
- completely reworked Patch 4 as it turned out that depending on the
kernel even sequential requests fly in out of order or we receive
a mix from different software queues.
v1->v2:
- add overflow checking for nb_sectors [Kevin]
- do not change the name of the macro of max mergable requests. [Fam]
RFC v2->v1:
- added Erics grammar corrections to Patch 4
- Patch 4
- reworked the IF tree to a SWITCH statement to make it easier
to understand in virtio_blk_handle_request
- stop merging if requests switch from read to write or vice
versa. e..g, otherwise we could introduce big delays as a small
read request could be followed by a lot of write requests
and the read requests sits there until the queue is empty.
RFC v1->RFC v2:
- completed Patch 1 by the example in qmp-commands.hx [Eric]
- used bool for merge in Patch 4 [Max]
- fixed a few typos in the commit msg of Patch 4 [Max]
- do not start merging and directly pass req[0]->qiov in case of num_reqs == 1
- avoid allocating memory for the multireq [Kevin]
- do not import block_int.h and add appropiate iface to block-backend [Kevin]
- removed debug output and added trace event for multireq [Kevin]
- fixed alloc hint for the merge qiov [Kevin]
- currently did not split virtio_submit_multireq into rw code since
the redundant code would now be much bigger part than in the original patch.
- added a merge_qiov to VirtioBlockRequest. Abusing the qiov was not possible
because it is initialized externally with guest memory [Kevin]
- added a pointer to VirtioBlockRequest to create a linked list
of VirtioBlockBlockRequests. This list is used to complete all
requests belonging to a multireq [Kevin]
Peter Lieven (4):
block: add accounting for merged requests
hw/virtio-blk: add a constant for max number of merged requests
block-backend: expose bs->bl.max_transfer_length
virtio-blk: introduce multiread
block.c | 2 +
block/accounting.c | 7 +
block/block-backend.c | 5 +
block/qapi.c | 2 +
hmp.c | 6 +-
hw/block/dataplane/virtio-blk.c | 8 +-
hw/block/virtio-blk.c | 288 +++++++++++++++++++++++++++-------------
include/block/accounting.h | 3 +
include/hw/virtio/virtio-blk.h | 17 ++-
include/sysemu/block-backend.h | 1 +
qapi/block-core.json | 9 +-
qmp-commands.hx | 22 ++-
trace-events | 1 +
13 files changed, 261 insertions(+), 110 deletions(-)
--
1.9.1
