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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1718127438; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Pic+NTGR2xDZGvJdSIIWUg6ye59mZnjGjver02Rud84=; b=JNBSZ6KpPTXcX2sYEBJ7C9irFR3XhyG3rWxJ2d5TGAVjEDgK+yYs35rHY9pIKFIwNyDNaN 6f/UEoFOMg38Q87ZIMVuhiZ8EYBCO7c/rteAI1lZgD+95vQuQrLQDzAVu+uZYu9NfBbLZP 8TrwoC51hthba4SI6uUgHdvJ6ZY1v/U= X-MC-Unique: FUDJC3w9OQaijwwYgsIhrA-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org Subject: [PULL 6/8] linux-aio: add IO_CMD_FDSYNC command support Date: Tue, 11 Jun 2024 19:36:56 +0200 Message-ID: <20240611173658.231831-7-kwolf@redhat.com> In-Reply-To: <20240611173658.231831-1-kwolf@redhat.com> References: <20240611173658.231831-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; 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charset="utf-8" From: Prasad Pandit Libaio defines IO_CMD_FDSYNC command to sync all outstanding asynchronous I/O operations, by flushing out file data to the disk storage. Enable linux-aio to submit such aio request. When using aio=3Dnative without fdsync() support, QEMU creates pthreads, and destroying these pthreads results in TLB flushes. In a real-time guest environment, TLB flushes cause a latency spike. This patch helps to avoid such spikes. Reviewed-by: Stefan Hajnoczi Signed-off-by: Prasad Pandit Message-ID: <20240425070412.37248-1-ppandit@redhat.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- include/block/raw-aio.h | 1 + block/file-posix.c | 9 +++++++++ block/linux-aio.c | 21 ++++++++++++++++++++- 3 files changed, 30 insertions(+), 1 deletion(-) diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h index 20e000b8ef..626706827f 100644 --- a/include/block/raw-aio.h +++ b/include/block/raw-aio.h @@ -60,6 +60,7 @@ void laio_cleanup(LinuxAioState *s); int coroutine_fn laio_co_submit(int fd, uint64_t offset, QEMUIOVector *qio= v, int type, uint64_t dev_max_batch); =20 +bool laio_has_fdsync(int); void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context); void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context); #endif diff --git a/block/file-posix.c b/block/file-posix.c index 5c46938936..be25e35ff6 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -159,6 +159,7 @@ typedef struct BDRVRawState { bool has_discard:1; bool has_write_zeroes:1; bool use_linux_aio:1; + bool has_laio_fdsync:1; bool use_linux_io_uring:1; int page_cache_inconsistent; /* errno from fdatasync failure */ bool has_fallocate; @@ -718,6 +719,9 @@ static int raw_open_common(BlockDriverState *bs, QDict = *options, ret =3D -EINVAL; goto fail; } + if (s->use_linux_aio) { + s->has_laio_fdsync =3D laio_has_fdsync(s->fd); + } #else if (s->use_linux_aio) { error_setg(errp, "aio=3Dnative was specified, but is not supported= " @@ -2598,6 +2602,11 @@ static int coroutine_fn raw_co_flush_to_disk(BlockDr= iverState *bs) if (raw_check_linux_io_uring(s)) { return luring_co_submit(bs, s->fd, 0, NULL, QEMU_AIO_FLUSH); } +#endif +#ifdef CONFIG_LINUX_AIO + if (s->has_laio_fdsync && raw_check_linux_aio(s)) { + return laio_co_submit(s->fd, 0, NULL, QEMU_AIO_FLUSH, 0); + } #endif return raw_thread_pool_submit(handle_aiocb_flush, &acb); } diff --git a/block/linux-aio.c b/block/linux-aio.c index ec05d946f3..e3b5ec9aba 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -384,6 +384,9 @@ static int laio_do_submit(int fd, struct qemu_laiocb *l= aiocb, off_t offset, case QEMU_AIO_READ: io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset); break; + case QEMU_AIO_FLUSH: + io_prep_fdsync(iocbs, fd); + break; /* Currently Linux kernel does not support other operations */ default: fprintf(stderr, "%s: invalid AIO request type 0x%x.\n", @@ -412,7 +415,7 @@ int coroutine_fn laio_co_submit(int fd, uint64_t offset= , QEMUIOVector *qiov, AioContext *ctx =3D qemu_get_current_aio_context(); struct qemu_laiocb laiocb =3D { .co =3D qemu_coroutine_self(), - .nbytes =3D qiov->size, + .nbytes =3D qiov ? qiov->size : 0, .ctx =3D aio_get_linux_aio(ctx), .ret =3D -EINPROGRESS, .is_read =3D (type =3D=3D QEMU_AIO_READ), @@ -486,3 +489,19 @@ void laio_cleanup(LinuxAioState *s) } g_free(s); } + +bool laio_has_fdsync(int fd) +{ + struct iocb cb; + struct iocb *cbs[] =3D {&cb, NULL}; + + io_context_t ctx =3D 0; + io_setup(1, &ctx); + + /* check if host kernel supports IO_CMD_FDSYNC */ + io_prep_fdsync(&cb, fd); + int ret =3D io_submit(ctx, 1, cbs); + + io_destroy(ctx); + return (ret =3D=3D -EINVAL) ? false : true; +} --=20 2.45.2