Re: [PATCH] cfq-iosched: reduce write depth only if sync was delayed

[Corrado Zoccolo]

On Fri, Dec 4, 2009 at 1:35 PM, Corrado Zoccolo <czoccolo@xxxxxxxxx> wrote:
> The introduction of ramp-up formula for async queue depths has
> slowed down dirty page reclaim, by reducing async write performance.
> This patch makes sure the formula kicks in only when sync request
> was recently delayed.
>
> Signed-off-by: Corrado Zoccolo <czoccolo@xxxxxxxxx>
> ---
> Âblock/cfq-iosched.c | Â Â9 +++++----
> Â1 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index b00ca4c..a594388 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -284,7 +284,7 @@ struct cfq_data {
> Â Â Â Â */
> Â Â Â Âstruct cfq_queue oom_cfqq;
>
> - Â Â Â unsigned long last_end_sync_rq;
> + Â Â Â unsigned long last_delayed_sync;
>
> Â Â Â Â/* List of cfq groups being managed on this device*/
> Â Â Â Âstruct hlist_head cfqg_list;
> @@ -2264,7 +2264,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd,
> struct cfq_queue *cfqq)
> Â Â Â Â * based on the last sync IO we serviced
> Â Â Â Â */
> Â Â Â Âif (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) {
> - Â Â Â Â Â Â Â unsigned long last_sync = jiffies - cfqd->last_end_sync_rq;
> + Â Â Â Â Â Â Â unsigned long last_sync = jiffies - cfqd->last_delayed_sync;
> Â Â Â Â Â Â Â Âunsigned int depth;
>
> Â Â Â Â Â Â Â Âdepth = last_sync / cfqd->cfq_slice[1];
> @@ -3272,7 +3272,8 @@ static void cfq_completed_request(struct request_queue
> *q, struct request *rq)
>
> Â Â Â Âif (sync) {
> Â Â Â Â Â Â Â ÂRQ_CIC(rq)->last_end_request = now;
> - Â Â Â Â Â Â Â cfqd->last_end_sync_rq = now;
> + Â Â Â Â Â Â Â if (time_after(rq->start_time + cfqd->cfq_fifo_expire[1], now))
> + Â Â Â Â Â Â Â Â Â Â Â cfqd->last_delayed_sync = now;

Sorry, the check be reversed (!time_after).

> Â Â Â Â}
>
> Â Â Â Â/*
> @@ -3706,7 +3707,7 @@ static void *cfq_init_queue(struct request_queue *q)
> Â Â Â Âcfqd->cfq_latency = 1;
> Â Â Â Âcfqd->cfq_group_isolation = 0;
> Â Â Â Âcfqd->hw_tag = -1;
> - Â Â Â cfqd->last_end_sync_rq = jiffies;
> + Â Â Â cfqd->last_delayed_sync = jiffies - HZ;
> Â Â Â Âreturn cfqd;
> Â}
>
> --
> 1.6.2.5
>
>
>
>
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