On Tue, Mar 27, 2012 at 07:43:17PM +0800, zwu.ker...@gmail.com wrote:
> From: Zhi Yong Wu <wu...@linux.vnet.ibm.com>
>
> Signed-off-by: Stefan Hajnoczi <stefa...@linux.vnet.ibm.com>
> Signed-off-by: Zhi Yong Wu <wu...@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
