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block: add blk_io_plug_call() API

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Introduce a new API for thread-local blk_io_plug() that does not
traverse the block graph. The goal is to make blk_io_plug() multi-queue
friendly.

Instead of having block drivers track whether or not we're in a plugged
section, provide an API that allows them to defer a function call until
we're unplugged: blk_io_plug_call(fn, opaque). If blk_io_plug_call() is
called multiple times with the same fn/opaque pair, then fn() is only
called once at the end of the function - resulting in batching.

This patch introduces the API and changes blk_io_plug()/blk_io_unplug().
blk_io_plug()/blk_io_unplug() no longer require a BlockBackend argument
because the plug state is now thread-local.

Later patches convert block drivers to blk_io_plug_call() and then we
can finally remove .bdrv_co_io_plug() once all block drivers have been
converted.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20230530180959.1108766-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-05-30 14:09:54 -04:00
parent c6a5fc2ac7
commit 41abca8c39
8 changed files with 173 additions and 41 deletions
Download patch file Download diff file Expand all files Collapse all files

8
hw/block/dataplane/xen-block.c
View file

@ -537,7 +537,7 @@ static bool xen_block_handle_requests(XenBlockDataPlane *dataplane)
* is below us.
*/
if (inflight_atstart > IO_PLUG_THRESHOLD) {
blk_io_plug(dataplane->blk);
blk_io_plug();
}
while (rc != rp) {
/* pull request from ring */
@ -577,12 +577,12 @@ static bool xen_block_handle_requests(XenBlockDataPlane *dataplane)
if (inflight_atstart > IO_PLUG_THRESHOLD &&
batched >= inflight_atstart) {
blk_io_unplug(dataplane->blk);
blk_io_unplug();
}
xen_block_do_aio(request);
if (inflight_atstart > IO_PLUG_THRESHOLD) {
if (batched >= inflight_atstart) {
blk_io_plug(dataplane->blk);
blk_io_plug();
batched = 0;
} else {
batched++;
@ -590,7 +590,7 @@ static bool xen_block_handle_requests(XenBlockDataPlane *dataplane)
}
}
if (inflight_atstart > IO_PLUG_THRESHOLD) {
blk_io_unplug(dataplane->blk);
blk_io_unplug();
}
return done_something;