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127 lines
4.6 KiB
127 lines
4.6 KiB
From 11faa773637f76f573f5320c063f7e55263c3a84 Mon Sep 17 00:00:00 2001
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From: Prasad Pandit <pjp@fedoraproject.org>
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Date: Thu, 25 Apr 2024 12:34:12 +0530
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Subject: [PATCH 1/5] linux-aio: add IO_CMD_FDSYNC command support
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RH-Author: Prasad Pandit <None>
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RH-MergeRequest: 260: linux-aio: add IO_CMD_FDSYNC command support
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RH-Jira: RHEL-51901
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Commit: [1/1] 2830edc801f9fbbc373631cf5b12a396f4b2bced (pjp/cs-qemu-kvm)
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Libaio defines IO_CMD_FDSYNC command to sync all outstanding
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asynchronous I/O operations, by flushing out file data to the
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disk storage. Enable linux-aio to submit such aio request.
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When using aio=native without fdsync() support, QEMU creates
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pthreads, and destroying these pthreads results in TLB flushes.
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In a real-time guest environment, TLB flushes cause a latency
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spike. This patch helps to avoid such spikes.
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Jira: https://issues.redhat.com/browse/RHEL-51901
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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Signed-off-by: Prasad Pandit <pjp@fedoraproject.org>
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Message-ID: <20240425070412.37248-1-ppandit@redhat.com>
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Reviewed-by: Kevin Wolf <kwolf@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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(cherry picked from commit 24687abf237e3c15816d689a8e4b08d7c3190dcb)
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Signed-off-by: Prasad Pandit <pjp@fedoraproject.org>
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---
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block/file-posix.c | 9 +++++++++
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block/linux-aio.c | 21 ++++++++++++++++++++-
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include/block/raw-aio.h | 1 +
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3 files changed, 30 insertions(+), 1 deletion(-)
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diff --git a/block/file-posix.c b/block/file-posix.c
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index 35684f7e21..9831b08fb6 100644
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--- a/block/file-posix.c
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+++ b/block/file-posix.c
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@@ -159,6 +159,7 @@ typedef struct BDRVRawState {
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bool has_discard:1;
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bool has_write_zeroes:1;
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bool use_linux_aio:1;
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+ bool has_laio_fdsync:1;
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bool use_linux_io_uring:1;
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int page_cache_inconsistent; /* errno from fdatasync failure */
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bool has_fallocate;
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@@ -718,6 +719,9 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,
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ret = -EINVAL;
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goto fail;
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}
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+ if (s->use_linux_aio) {
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+ s->has_laio_fdsync = laio_has_fdsync(s->fd);
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+ }
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#else
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if (s->use_linux_aio) {
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error_setg(errp, "aio=native was specified, but is not supported "
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@@ -2599,6 +2603,11 @@ static int coroutine_fn raw_co_flush_to_disk(BlockDriverState *bs)
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if (raw_check_linux_io_uring(s)) {
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return luring_co_submit(bs, s->fd, 0, NULL, QEMU_AIO_FLUSH);
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}
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+#endif
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+#ifdef CONFIG_LINUX_AIO
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+ if (s->has_laio_fdsync && raw_check_linux_aio(s)) {
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+ return laio_co_submit(s->fd, 0, NULL, QEMU_AIO_FLUSH, 0);
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+ }
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#endif
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return raw_thread_pool_submit(handle_aiocb_flush, &acb);
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}
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diff --git a/block/linux-aio.c b/block/linux-aio.c
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index ec05d946f3..e3b5ec9aba 100644
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--- a/block/linux-aio.c
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+++ b/block/linux-aio.c
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@@ -384,6 +384,9 @@ static int laio_do_submit(int fd, struct qemu_laiocb *laiocb, off_t offset,
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case QEMU_AIO_READ:
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io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset);
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break;
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+ case QEMU_AIO_FLUSH:
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+ io_prep_fdsync(iocbs, fd);
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+ break;
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/* Currently Linux kernel does not support other operations */
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default:
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fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
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@@ -412,7 +415,7 @@ int coroutine_fn laio_co_submit(int fd, uint64_t offset, QEMUIOVector *qiov,
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AioContext *ctx = qemu_get_current_aio_context();
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struct qemu_laiocb laiocb = {
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.co = qemu_coroutine_self(),
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- .nbytes = qiov->size,
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+ .nbytes = qiov ? qiov->size : 0,
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.ctx = aio_get_linux_aio(ctx),
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.ret = -EINPROGRESS,
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.is_read = (type == QEMU_AIO_READ),
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@@ -486,3 +489,19 @@ void laio_cleanup(LinuxAioState *s)
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}
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g_free(s);
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}
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+
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+bool laio_has_fdsync(int fd)
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+{
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+ struct iocb cb;
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+ struct iocb *cbs[] = {&cb, NULL};
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+
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+ io_context_t ctx = 0;
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+ io_setup(1, &ctx);
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+
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+ /* check if host kernel supports IO_CMD_FDSYNC */
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+ io_prep_fdsync(&cb, fd);
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+ int ret = io_submit(ctx, 1, cbs);
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+
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+ io_destroy(ctx);
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+ return (ret == -EINVAL) ? false : true;
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+}
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diff --git a/include/block/raw-aio.h b/include/block/raw-aio.h
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index 20e000b8ef..626706827f 100644
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--- a/include/block/raw-aio.h
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+++ b/include/block/raw-aio.h
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@@ -60,6 +60,7 @@ void laio_cleanup(LinuxAioState *s);
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int coroutine_fn laio_co_submit(int fd, uint64_t offset, QEMUIOVector *qiov,
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int type, uint64_t dev_max_batch);
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+bool laio_has_fdsync(int);
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void laio_detach_aio_context(LinuxAioState *s, AioContext *old_context);
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void laio_attach_aio_context(LinuxAioState *s, AioContext *new_context);
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#endif
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--
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2.39.3
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