| Message ID | 1332848597-8307-1-git-send-email-zwu.kernel@gmail.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Mar 27, 2012 at 07:43:17PM +0800, zwu.kernel@gmail.com wrote: > From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> > > Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> > Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> > --- > block.c | 10 ++++++++++ > 1 files changed, 10 insertions(+), 0 deletions(-) I tested this successfully with if=virtio and if=ide. > diff --git a/block.c b/block.c > index 1fbf4dd..f0b4f38 100644 > --- a/block.c > +++ b/block.c > @@ -1477,6 +1477,12 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf, > > qemu_iovec_init_external(&qiov, &iov, 1); > Please add a comment explaining that synchronous I/O cannot be throttled because timers don't work in that context. > + if (bs->io_limits_enabled) { > + fprintf(stderr, "Disabling I/O throttling on '%s' due " > + "to synchronous I/O.\n", bdrv_get_device_name(bs)); > + bdrv_io_limits_disable(bs); > + } > + > if (qemu_in_coroutine()) { > /* Fast-path if already in coroutine context */ > bdrv_rw_co_entry(&rwco); > @@ -1983,10 +1989,14 @@ static int guess_disk_lchs(BlockDriverState *bs, > struct partition *p; > uint32_t nr_sects; > uint64_t nb_sectors; > + bool enabled; > > bdrv_get_geometry(bs, &nb_sectors); > > + enabled = bs->io_limits_enabled; > + bs->io_limits_enabled = false; > ret = bdrv_read(bs, 0, buf, 1); > + bs->io_limits_enabled = enabled; Please add a comment explaining that this function is called during startup, even for storage interfaces that use asynchronous I/O functions. Therefore we explicitly disable throttling *temporarily*, not permanently, here. Stefan
On Fri, Mar 30, 2012 at 3:13 PM, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> wrote: > On Tue, Mar 27, 2012 at 07:43:17PM +0800, zwu.kernel@gmail.com wrote: >> From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> >> >> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com> >> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> >> --- >> block.c | 10 ++++++++++ >> 1 files changed, 10 insertions(+), 0 deletions(-) > > I tested this successfully with if=virtio and if=ide. > >> diff --git a/block.c b/block.c >> index 1fbf4dd..f0b4f38 100644 >> --- a/block.c >> +++ b/block.c >> @@ -1477,6 +1477,12 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf, >> >> qemu_iovec_init_external(&qiov, &iov, 1); >> > > Please add a comment explaining that synchronous I/O cannot be throttled > because timers don't work in that context. > >> + if (bs->io_limits_enabled) { >> + fprintf(stderr, "Disabling I/O throttling on '%s' due " >> + "to synchronous I/O.\n", bdrv_get_device_name(bs)); >> + bdrv_io_limits_disable(bs); >> + } >> + >> if (qemu_in_coroutine()) { >> /* Fast-path if already in coroutine context */ >> bdrv_rw_co_entry(&rwco); >> @@ -1983,10 +1989,14 @@ static int guess_disk_lchs(BlockDriverState *bs, >> struct partition *p; >> uint32_t nr_sects; >> uint64_t nb_sectors; >> + bool enabled; >> >> bdrv_get_geometry(bs, &nb_sectors); >> >> + enabled = bs->io_limits_enabled; >> + bs->io_limits_enabled = false; >> ret = bdrv_read(bs, 0, buf, 1); >> + bs->io_limits_enabled = enabled; > > Please add a comment explaining that this function is called during > startup, even for storage interfaces that use asynchronous I/O > functions. Therefore we explicitly disable throttling *temporarily*, > not permanently, here. thanks for your comments, pls see v3. > > Stefan >
diff --git a/block.c b/block.c index 1fbf4dd..f0b4f38 100644 --- a/block.c +++ b/block.c @@ -1477,6 +1477,12 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf, qemu_iovec_init_external(&qiov, &iov, 1); + if (bs->io_limits_enabled) { + fprintf(stderr, "Disabling I/O throttling on '%s' due " + "to synchronous I/O.\n", bdrv_get_device_name(bs)); + bdrv_io_limits_disable(bs); + } + if (qemu_in_coroutine()) { /* Fast-path if already in coroutine context */ bdrv_rw_co_entry(&rwco); @@ -1983,10 +1989,14 @@ static int guess_disk_lchs(BlockDriverState *bs, struct partition *p; uint32_t nr_sects; uint64_t nb_sectors; + bool enabled; bdrv_get_geometry(bs, &nb_sectors); + enabled = bs->io_limits_enabled; + bs->io_limits_enabled = false; ret = bdrv_read(bs, 0, buf, 1); + bs->io_limits_enabled = enabled; if (ret < 0) return -1; /* test msdos magic */