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| author | Sam Li <faithilikerun@gmail.com> | 2022-05-31 18:50:11 +0800 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2022-06-15 14:50:41 +0100 |
| commit | e2848bc574fe2715c694bf8fe9a1ba7f78a1125a (patch) | |
| tree | d9102f20555ac4a6d03fae58175c977a988422bd | |
| parent | 9e4067b8a41514c8f5715a2c735c3ac03e5d70c8 (diff) | |
| download | qemu-e2848bc574fe2715c694bf8fe9a1ba7f78a1125a.zip qemu-e2848bc574fe2715c694bf8fe9a1ba7f78a1125a.tar.gz qemu-e2848bc574fe2715c694bf8fe9a1ba7f78a1125a.tar.bz2 | |
Use io_uring_register_ring_fd() to skip fd operations
Linux recently added a new io_uring(7) optimization API that QEMU
doesn't take advantage of yet. The liburing library that QEMU uses
has added a corresponding new API calling io_uring_register_ring_fd().
When this API is called after creating the ring, the io_uring_submit()
library function passes a flag to the io_uring_enter(2) syscall
allowing it to skip the ring file descriptor fdget()/fdput()
operations. This saves some CPU cycles.
Signed-off-by: Sam Li <faithilikerun@gmail.com>
Message-id: 20220531105011.111082-1-faithilikerun@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
| -rw-r--r-- | block/io_uring.c | 12 | ||||
| -rw-r--r-- | meson.build | 1 |
2 files changed, 12 insertions, 1 deletions
diff --git a/block/io_uring.c b/block/io_uring.c index 0b40151..d48e472 100644 --- a/block/io_uring.c +++ b/block/io_uring.c @@ -18,6 +18,7 @@ #include "qapi/error.h" #include "trace.h" + /* io_uring ring size */ #define MAX_ENTRIES 128 @@ -434,8 +435,17 @@ LuringState *luring_init(Error **errp) } ioq_init(&s->io_q); - return s; +#ifdef CONFIG_LIBURING_REGISTER_RING_FD + if (io_uring_register_ring_fd(&s->ring) < 0) { + /* + * Only warn about this error: we will fallback to the non-optimized + * io_uring operations. + */ + warn_report("failed to register linux io_uring ring file descriptor"); + } +#endif + return s; } void luring_cleanup(LuringState *s) diff --git a/meson.build b/meson.build index 0c2e11f..9e65cc5 100644 --- a/meson.build +++ b/meson.build @@ -1752,6 +1752,7 @@ config_host_data.set('CONFIG_LIBNFS', libnfs.found()) config_host_data.set('CONFIG_LIBSSH', libssh.found()) config_host_data.set('CONFIG_LINUX_AIO', libaio.found()) config_host_data.set('CONFIG_LINUX_IO_URING', linux_io_uring.found()) +config_host_data.set('CONFIG_LIBURING_REGISTER_RING_FD', cc.has_function('io_uring_register_ring_fd', prefix: '#include <liburing.h>', dependencies:linux_io_uring)) config_host_data.set('CONFIG_LIBPMEM', libpmem.found()) config_host_data.set('CONFIG_NUMA', numa.found()) config_host_data.set('CONFIG_OPENGL', opengl.found()) |