Hello, friendly ping...
Thanks.
On 2022/6/3 17:20, Chengming Zhou wrote:
> Since latency Qos detection doesn't account for IOs which
> are in-flight for longer than a period, we detect them by
> comparing vdone against period start. If lagging behind
> IOs from past periods, don't increase vrate, but don't let
> cmds which take a very long time pin lagging for too long.
>
> The current code compares vdone against (vnow - period_vtime),
> which is thought to be the period start. But the earliest
> period start should be (vnow - period_vtime - margins.target).
>
> And we will slide forward vtime and vdone on each period timer,
> so we can't depend on vtime to check if the iocg has pinned
> lagging for longer than MAX_LAGGING_PERIODS.
>
> This patch adds lagging_periods in iocg to record how long
> the iocg has pinned lagging, will not be thought as lagging
> if longer than MAX_LAGGING_PERIODS.
>
> Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> ---
> v2:
> - add lagging_periods to check very long lagging iocg.
> ---
> block/blk-iocost.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/block/blk-iocost.c b/block/blk-iocost.c
> index 33a11ba971ea..998bb38ffb37 100644
> --- a/block/blk-iocost.c
> +++ b/block/blk-iocost.c
> @@ -541,6 +541,8 @@ struct ioc_gq {
> u64 indebt_since;
> u64 indelay_since;
>
> + int lagging_periods;
> +
> /* this iocg's depth in the hierarchy and ancestors including self */
> int level;
> struct ioc_gq *ancestors[];
> @@ -2257,10 +2259,13 @@ static void ioc_timer_fn(struct timer_list *timer)
> if ((ppm_rthr != MILLION || ppm_wthr != MILLION) &&
> !atomic_read(&iocg_to_blkg(iocg)->use_delay) &&
> time_after64(vtime, vdone) &&
> - time_after64(vtime, now.vnow -
> - MAX_LAGGING_PERIODS * period_vtime) &&
> - time_before64(vdone, now.vnow - period_vtime))
> - nr_lagging++;
> + time_before64(vdone, ioc->period_at_vtime - ioc->margins.target)) {
> + if (iocg->lagging_periods < MAX_LAGGING_PERIODS) {
> + nr_lagging++;
> + iocg->lagging_periods++;
> + }
> + } else if (iocg->lagging_periods)
> + iocg->lagging_periods = 0;
>
> /*
> * Determine absolute usage factoring in in-flight IOs to avoid
