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Re: [Qemu-devel] [PATCH 1/1] mirror: fix request throttling in drive-mir
From: |
Jeff Cody |
Subject: |
Re: [Qemu-devel] [PATCH 1/1] mirror: fix request throttling in drive-mirror |
Date: |
Thu, 30 Jun 2016 12:17:47 -0400 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
On Wed, Jun 22, 2016 at 03:35:27PM +0300, Denis V. Lunev wrote:
> There are 2 deficiencies here:
> - mirror_iteration could start several requests inside. Thus we could
> simply have more in_flight requests than MAX_IN_FLIGHT.
> - keeping this in mind throttling in mirror_run which is checking
> s->in_flight == MAX_IN_FLIGHT is wrong.
>
> The patch adds the check and throttling into mirror_iteration and fixes
> the check in mirror_run() to be sure.
>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Jeff Cody <address@hidden>
> CC: Kevin Wolf <address@hidden>
> CC: Max Reitz <address@hidden>
> ---
> block/mirror.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index a04ed9c..e881ef6 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -399,6 +399,11 @@ static uint64_t coroutine_fn
> mirror_iteration(MirrorBlockJob *s)
> }
> }
>
> + while (s->in_flight >= MAX_IN_FLIGHT) {
> + trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
> + mirror_wait_for_io(s);
> + }
> +
> mirror_clip_sectors(s, sector_num, &io_sectors);
> switch (mirror_method) {
> case MIRROR_METHOD_COPY:
> @@ -634,7 +639,7 @@ static void coroutine_fn mirror_run(void *opaque)
> */
> if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns <
> SLICE_TIME &&
> s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
> - if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
> + if (s->in_flight >= MAX_IN_FLIGHT || s->buf_free_count == 0 ||
> (cnt == 0 && s->in_flight > 0)) {
> trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
> mirror_wait_for_io(s);
> --
> 2.1.4
>
Reviewed-by: Jeff Cody <address@hidden>