From: Stefano Garzarella <sgarz...@redhat.com> Commit d7ddd0a161 ("linux-aio: limit the batch size using `aio-max-batch` parameter") added a way to limit the batch size of Linux AIO backend for the entire AIO context.
The same AIO context can be shared by multiple devices, so latency-sensitive devices may want to limit the batch size even more to avoid increasing latency. For this reason we add the `aio-max-batch` option to the file backend, which will be used by the next commits to limit the size of batches including requests generated by this device. Suggested-by: Kevin Wolf <kw...@redhat.com> Reviewed-by: Kevin Wolf <kw...@redhat.com> Signed-off-by: Stefano Garzarella <sgarz...@redhat.com> Message-Id: <20211026162346.253081-2-sgarz...@redhat.com> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com> Signed-off-by: Kevin Wolf <kw...@redhat.com> --- qapi/block-core.json | 7 +++++++ block/file-posix.c | 9 +++++++++ 2 files changed, 16 insertions(+) diff --git a/qapi/block-core.json b/qapi/block-core.json index ce2c1352cb..ea36e0038c 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -2939,6 +2939,12 @@ # for this device (default: none, forward the commands via SG_IO; # since 2.11) # @aio: AIO backend (default: threads) (since: 2.8) +# @aio-max-batch: maximum number of requests to batch together into a single +# submission in the AIO backend. The smallest value between +# this and the aio-max-batch value of the IOThread object is +# chosen. +# 0 means that the AIO backend will handle it automatically. +# (default: 0, since 6.2) # @locking: whether to enable file locking. If set to 'auto', only enable # when Open File Descriptor (OFD) locking API is available # (default: auto, since 2.10) @@ -2968,6 +2974,7 @@ '*pr-manager': 'str', '*locking': 'OnOffAuto', '*aio': 'BlockdevAioOptions', + '*aio-max-batch': 'int', '*drop-cache': {'type': 'bool', 'if': 'CONFIG_LINUX'}, '*x-check-cache-dropped': { 'type': 'bool', diff --git a/block/file-posix.c b/block/file-posix.c index 6def2a4cba..7a289a9481 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -150,6 +150,8 @@ typedef struct BDRVRawState { uint64_t locked_perm; uint64_t locked_shared_perm; + uint64_t aio_max_batch; + int perm_change_fd; int perm_change_flags; BDRVReopenState *reopen_state; @@ -530,6 +532,11 @@ static QemuOptsList raw_runtime_opts = { .type = QEMU_OPT_STRING, .help = "host AIO implementation (threads, native, io_uring)", }, + { + .name = "aio-max-batch", + .type = QEMU_OPT_NUMBER, + .help = "AIO max batch size (0 = auto handled by AIO backend, default: 0)", + }, { .name = "locking", .type = QEMU_OPT_STRING, @@ -609,6 +616,8 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, s->use_linux_io_uring = (aio == BLOCKDEV_AIO_OPTIONS_IO_URING); #endif + s->aio_max_batch = qemu_opt_get_number(opts, "aio-max-batch", 0); + locking = qapi_enum_parse(&OnOffAuto_lookup, qemu_opt_get(opts, "locking"), ON_OFF_AUTO_AUTO, &local_err); -- 2.31.1