* [PATCH v2][RESEND] Allow RT requests to pre-empt ongoing BE timeslice in CFQ.
@ 2009-01-28 6:05 Divyesh Shah
2009-01-28 6:17 ` Divyesh Shah
0 siblings, 1 reply; 4+ messages in thread
From: Divyesh Shah @ 2009-01-28 6:05 UTC (permalink / raw)
To: jens.axboe, mikew, nauman, linux-kernel
This patch adds the ability to pre-empt an ongoing BE timeslice when a RT
request is waiting for the current timeslice to complete. This reduces the
wait time to disk for RT requests from an upper bound of 4 (current value
of cfq_quantum) to 1 disk request.
Signed-off-by: Divyesh Shah <dpshah@google.com>
---
Applied Jens' suggeested changes to avoid the rb lookup and use !cfq_class_rt()
and retested.
Latency(secs) for the RT task when doing sequential reads from 10G file.
| only RT | RT + BE | RT + BE + this patch
small (512 byte) reads | 143 | 163 | 145
large (1Mb) reads | 142 | 158 | 146
block/cfq-iosched.c | 39 ++++++++++++++++++++++++++++++++++++++-
1 files changed, 38 insertions(+), 1 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e8525fa..5fec9e5 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -84,6 +84,11 @@ struct cfq_data {
*/
struct cfq_rb_root service_tree;
unsigned int busy_queues;
+ /*
+ * Used to track any pending rt requests so we can pre-empt current
+ * non-RT cfqq in service when this value is non-zero.
+ */
+ unsigned int busy_rt_queues;
int rq_in_driver;
int sync_flight;
@@ -562,6 +567,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
BUG_ON(cfq_cfqq_on_rr(cfqq));
cfq_mark_cfqq_on_rr(cfqq);
cfqd->busy_queues++;
+ if (cfq_class_rt(cfqq))
+ cfqd->busy_rt_queues++;
cfq_resort_rr_list(cfqd, cfqq);
}
@@ -581,6 +588,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
+ if (cfq_class_rt(cfqq))
+ cfqd->busy_rt_queues--;
}
/*
@@ -1005,6 +1014,20 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
goto expire;
/*
+ * If we have a RT cfqq waiting, then we pre-empt the current non-rt
+ * cfqq.
+ */
+ if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) {
+ /*
+ * We simulate this as cfqq timed out so that it gets to bank
+ * the remaining of its time slice.
+ */
+ cfq_log_cfqq(cfqd, cfqq, "preempt");
+ cfq_slice_expired(cfqd, 1);
+ goto new_queue;
+ }
+
+ /*
* The active queue has requests and isn't expired, allow it to
* dispatch.
*/
@@ -1067,6 +1090,13 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
if (RB_EMPTY_ROOT(&cfqq->sort_list))
break;
+ /*
+ * If there is a non-empty RT cfqq waiting for current
+ * cfqq's timeslice to complete, pre-empt this cfqq
+ */
+ if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues)
+ break;
+
} while (dispatched < max_dispatch);
/*
@@ -1801,6 +1831,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
if (rq_is_meta(rq) && !cfqq->meta_pending)
return 1;
+ /*
+ * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
+ */
+ if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
+ return 1;
+
if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
return 0;
@@ -1870,7 +1906,8 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
/*
* not the active queue - expire current slice if it is
* idle and has expired it's mean thinktime or this new queue
- * has some old slice time left and is of higher priority
+ * has some old slice time left and is of higher priority or
+ * this new queue is RT and the current one is BE
*/
cfq_preempt_queue(cfqd, cfqq);
cfq_mark_cfqq_must_dispatch(cfqq);
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2][RESEND] Allow RT requests to pre-empt ongoing BE timeslice in CFQ.
2009-01-28 6:05 [PATCH v2][RESEND] Allow RT requests to pre-empt ongoing BE timeslice in CFQ Divyesh Shah
@ 2009-01-28 6:17 ` Divyesh Shah
2009-01-30 11:26 ` Jens Axboe
0 siblings, 1 reply; 4+ messages in thread
From: Divyesh Shah @ 2009-01-28 6:17 UTC (permalink / raw)
To: jens.axboe, mikew, nauman, linux-kernel
+ Jens Axboe
On Wed, Jan 28, 2009 at 11:35 AM, Divyesh Shah <dpshah@google.com> wrote:
> This patch adds the ability to pre-empt an ongoing BE timeslice when a RT
> request is waiting for the current timeslice to complete. This reduces the
> wait time to disk for RT requests from an upper bound of 4 (current value
> of cfq_quantum) to 1 disk request.
>
> Signed-off-by: Divyesh Shah <dpshah@google.com>
> ---
> Applied Jens' suggeested changes to avoid the rb lookup and use !cfq_class_rt()
> and retested.
>
> Latency(secs) for the RT task when doing sequential reads from 10G file.
> | only RT | RT + BE | RT + BE + this patch
> small (512 byte) reads | 143 | 163 | 145
> large (1Mb) reads | 142 | 158 | 146
>
> block/cfq-iosched.c | 39 ++++++++++++++++++++++++++++++++++++++-
> 1 files changed, 38 insertions(+), 1 deletions(-)
>
> diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> index e8525fa..5fec9e5 100644
> --- a/block/cfq-iosched.c
> +++ b/block/cfq-iosched.c
> @@ -84,6 +84,11 @@ struct cfq_data {
> */
> struct cfq_rb_root service_tree;
> unsigned int busy_queues;
> + /*
> + * Used to track any pending rt requests so we can pre-empt current
> + * non-RT cfqq in service when this value is non-zero.
> + */
> + unsigned int busy_rt_queues;
>
> int rq_in_driver;
> int sync_flight;
> @@ -562,6 +567,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> BUG_ON(cfq_cfqq_on_rr(cfqq));
> cfq_mark_cfqq_on_rr(cfqq);
> cfqd->busy_queues++;
> + if (cfq_class_rt(cfqq))
> + cfqd->busy_rt_queues++;
>
> cfq_resort_rr_list(cfqd, cfqq);
> }
> @@ -581,6 +588,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
>
> BUG_ON(!cfqd->busy_queues);
> cfqd->busy_queues--;
> + if (cfq_class_rt(cfqq))
> + cfqd->busy_rt_queues--;
> }
>
> /*
> @@ -1005,6 +1014,20 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
> goto expire;
>
> /*
> + * If we have a RT cfqq waiting, then we pre-empt the current non-rt
> + * cfqq.
> + */
> + if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) {
> + /*
> + * We simulate this as cfqq timed out so that it gets to bank
> + * the remaining of its time slice.
> + */
> + cfq_log_cfqq(cfqd, cfqq, "preempt");
> + cfq_slice_expired(cfqd, 1);
> + goto new_queue;
> + }
> +
> + /*
> * The active queue has requests and isn't expired, allow it to
> * dispatch.
> */
> @@ -1067,6 +1090,13 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> if (RB_EMPTY_ROOT(&cfqq->sort_list))
> break;
>
> + /*
> + * If there is a non-empty RT cfqq waiting for current
> + * cfqq's timeslice to complete, pre-empt this cfqq
> + */
> + if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues)
> + break;
> +
> } while (dispatched < max_dispatch);
>
> /*
> @@ -1801,6 +1831,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
> if (rq_is_meta(rq) && !cfqq->meta_pending)
> return 1;
>
> + /*
> + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
> + */
> + if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
> + return 1;
> +
> if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
> return 0;
>
> @@ -1870,7 +1906,8 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> /*
> * not the active queue - expire current slice if it is
> * idle and has expired it's mean thinktime or this new queue
> - * has some old slice time left and is of higher priority
> + * has some old slice time left and is of higher priority or
> + * this new queue is RT and the current one is BE
> */
> cfq_preempt_queue(cfqd, cfqq);
> cfq_mark_cfqq_must_dispatch(cfqq);
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2][RESEND] Allow RT requests to pre-empt ongoing BE timeslice in CFQ.
2009-01-28 6:17 ` Divyesh Shah
@ 2009-01-30 11:26 ` Jens Axboe
2009-01-30 11:49 ` Jens Axboe
0 siblings, 1 reply; 4+ messages in thread
From: Jens Axboe @ 2009-01-30 11:26 UTC (permalink / raw)
To: Divyesh Shah; +Cc: mikew, nauman, linux-kernel
On Wed, Jan 28 2009, Divyesh Shah wrote:
Strange, I was pretty sure this was added, but apparently not. Can you
resend a non-whitespace damaged version and I'll make sure to add it to
the mix.
> + Jens Axboe
>
> On Wed, Jan 28, 2009 at 11:35 AM, Divyesh Shah <dpshah@google.com> wrote:
> > This patch adds the ability to pre-empt an ongoing BE timeslice when a RT
> > request is waiting for the current timeslice to complete. This reduces the
> > wait time to disk for RT requests from an upper bound of 4 (current value
> > of cfq_quantum) to 1 disk request.
> >
> > Signed-off-by: Divyesh Shah <dpshah@google.com>
> > ---
> > Applied Jens' suggeested changes to avoid the rb lookup and use !cfq_class_rt()
> > and retested.
> >
> > Latency(secs) for the RT task when doing sequential reads from 10G file.
> > | only RT | RT + BE | RT + BE + this patch
> > small (512 byte) reads | 143 | 163 | 145
> > large (1Mb) reads | 142 | 158 | 146
> >
> > block/cfq-iosched.c | 39 ++++++++++++++++++++++++++++++++++++++-
> > 1 files changed, 38 insertions(+), 1 deletions(-)
> >
> > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> > index e8525fa..5fec9e5 100644
> > --- a/block/cfq-iosched.c
> > +++ b/block/cfq-iosched.c
> > @@ -84,6 +84,11 @@ struct cfq_data {
> > */
> > struct cfq_rb_root service_tree;
> > unsigned int busy_queues;
> > + /*
> > + * Used to track any pending rt requests so we can pre-empt current
> > + * non-RT cfqq in service when this value is non-zero.
> > + */
> > + unsigned int busy_rt_queues;
> >
> > int rq_in_driver;
> > int sync_flight;
> > @@ -562,6 +567,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> > BUG_ON(cfq_cfqq_on_rr(cfqq));
> > cfq_mark_cfqq_on_rr(cfqq);
> > cfqd->busy_queues++;
> > + if (cfq_class_rt(cfqq))
> > + cfqd->busy_rt_queues++;
> >
> > cfq_resort_rr_list(cfqd, cfqq);
> > }
> > @@ -581,6 +588,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> >
> > BUG_ON(!cfqd->busy_queues);
> > cfqd->busy_queues--;
> > + if (cfq_class_rt(cfqq))
> > + cfqd->busy_rt_queues--;
> > }
> >
> > /*
> > @@ -1005,6 +1014,20 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
> > goto expire;
> >
> > /*
> > + * If we have a RT cfqq waiting, then we pre-empt the current non-rt
> > + * cfqq.
> > + */
> > + if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) {
> > + /*
> > + * We simulate this as cfqq timed out so that it gets to bank
> > + * the remaining of its time slice.
> > + */
> > + cfq_log_cfqq(cfqd, cfqq, "preempt");
> > + cfq_slice_expired(cfqd, 1);
> > + goto new_queue;
> > + }
> > +
> > + /*
> > * The active queue has requests and isn't expired, allow it to
> > * dispatch.
> > */
> > @@ -1067,6 +1090,13 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> > if (RB_EMPTY_ROOT(&cfqq->sort_list))
> > break;
> >
> > + /*
> > + * If there is a non-empty RT cfqq waiting for current
> > + * cfqq's timeslice to complete, pre-empt this cfqq
> > + */
> > + if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues)
> > + break;
> > +
> > } while (dispatched < max_dispatch);
> >
> > /*
> > @@ -1801,6 +1831,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
> > if (rq_is_meta(rq) && !cfqq->meta_pending)
> > return 1;
> >
> > + /*
> > + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
> > + */
> > + if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
> > + return 1;
> > +
> > if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
> > return 0;
> >
> > @@ -1870,7 +1906,8 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> > /*
> > * not the active queue - expire current slice if it is
> > * idle and has expired it's mean thinktime or this new queue
> > - * has some old slice time left and is of higher priority
> > + * has some old slice time left and is of higher priority or
> > + * this new queue is RT and the current one is BE
> > */
> > cfq_preempt_queue(cfqd, cfqq);
> > cfq_mark_cfqq_must_dispatch(cfqq);
> >
> >
--
Jens Axboe
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2][RESEND] Allow RT requests to pre-empt ongoing BE timeslice in CFQ.
2009-01-30 11:26 ` Jens Axboe
@ 2009-01-30 11:49 ` Jens Axboe
0 siblings, 0 replies; 4+ messages in thread
From: Jens Axboe @ 2009-01-30 11:49 UTC (permalink / raw)
To: Divyesh Shah; +Cc: mikew, nauman, linux-kernel
On Fri, Jan 30 2009, Jens Axboe wrote:
> On Wed, Jan 28 2009, Divyesh Shah wrote:
>
> Strange, I was pretty sure this was added, but apparently not. Can you
> resend a non-whitespace damaged version and I'll make sure to add it to
> the mix.
Nevermind, found non-cc'ed original on lkml, which wasn't whitespace
damaged.
>
>
> > + Jens Axboe
> >
> > On Wed, Jan 28, 2009 at 11:35 AM, Divyesh Shah <dpshah@google.com> wrote:
> > > This patch adds the ability to pre-empt an ongoing BE timeslice when a RT
> > > request is waiting for the current timeslice to complete. This reduces the
> > > wait time to disk for RT requests from an upper bound of 4 (current value
> > > of cfq_quantum) to 1 disk request.
> > >
> > > Signed-off-by: Divyesh Shah <dpshah@google.com>
> > > ---
> > > Applied Jens' suggeested changes to avoid the rb lookup and use !cfq_class_rt()
> > > and retested.
> > >
> > > Latency(secs) for the RT task when doing sequential reads from 10G file.
> > > | only RT | RT + BE | RT + BE + this patch
> > > small (512 byte) reads | 143 | 163 | 145
> > > large (1Mb) reads | 142 | 158 | 146
> > >
> > > block/cfq-iosched.c | 39 ++++++++++++++++++++++++++++++++++++++-
> > > 1 files changed, 38 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
> > > index e8525fa..5fec9e5 100644
> > > --- a/block/cfq-iosched.c
> > > +++ b/block/cfq-iosched.c
> > > @@ -84,6 +84,11 @@ struct cfq_data {
> > > */
> > > struct cfq_rb_root service_tree;
> > > unsigned int busy_queues;
> > > + /*
> > > + * Used to track any pending rt requests so we can pre-empt current
> > > + * non-RT cfqq in service when this value is non-zero.
> > > + */
> > > + unsigned int busy_rt_queues;
> > >
> > > int rq_in_driver;
> > > int sync_flight;
> > > @@ -562,6 +567,8 @@ static void cfq_add_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> > > BUG_ON(cfq_cfqq_on_rr(cfqq));
> > > cfq_mark_cfqq_on_rr(cfqq);
> > > cfqd->busy_queues++;
> > > + if (cfq_class_rt(cfqq))
> > > + cfqd->busy_rt_queues++;
> > >
> > > cfq_resort_rr_list(cfqd, cfqq);
> > > }
> > > @@ -581,6 +588,8 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
> > >
> > > BUG_ON(!cfqd->busy_queues);
> > > cfqd->busy_queues--;
> > > + if (cfq_class_rt(cfqq))
> > > + cfqd->busy_rt_queues--;
> > > }
> > >
> > > /*
> > > @@ -1005,6 +1014,20 @@ static struct cfq_queue *cfq_select_queue(struct cfq_data *cfqd)
> > > goto expire;
> > >
> > > /*
> > > + * If we have a RT cfqq waiting, then we pre-empt the current non-rt
> > > + * cfqq.
> > > + */
> > > + if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues) {
> > > + /*
> > > + * We simulate this as cfqq timed out so that it gets to bank
> > > + * the remaining of its time slice.
> > > + */
> > > + cfq_log_cfqq(cfqd, cfqq, "preempt");
> > > + cfq_slice_expired(cfqd, 1);
> > > + goto new_queue;
> > > + }
> > > +
> > > + /*
> > > * The active queue has requests and isn't expired, allow it to
> > > * dispatch.
> > > */
> > > @@ -1067,6 +1090,13 @@ __cfq_dispatch_requests(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> > > if (RB_EMPTY_ROOT(&cfqq->sort_list))
> > > break;
> > >
> > > + /*
> > > + * If there is a non-empty RT cfqq waiting for current
> > > + * cfqq's timeslice to complete, pre-empt this cfqq
> > > + */
> > > + if (!cfq_class_rt(cfqq) && cfqd->busy_rt_queues)
> > > + break;
> > > +
> > > } while (dispatched < max_dispatch);
> > >
> > > /*
> > > @@ -1801,6 +1831,12 @@ cfq_should_preempt(struct cfq_data *cfqd, struct cfq_queue *new_cfqq,
> > > if (rq_is_meta(rq) && !cfqq->meta_pending)
> > > return 1;
> > >
> > > + /*
> > > + * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
> > > + */
> > > + if (cfq_class_rt(new_cfqq) && !cfq_class_rt(cfqq))
> > > + return 1;
> > > +
> > > if (!cfqd->active_cic || !cfq_cfqq_wait_request(cfqq))
> > > return 0;
> > >
> > > @@ -1870,7 +1906,8 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq,
> > > /*
> > > * not the active queue - expire current slice if it is
> > > * idle and has expired it's mean thinktime or this new queue
> > > - * has some old slice time left and is of higher priority
> > > + * has some old slice time left and is of higher priority or
> > > + * this new queue is RT and the current one is BE
> > > */
> > > cfq_preempt_queue(cfqd, cfqq);
> > > cfq_mark_cfqq_must_dispatch(cfqq);
> > >
> > >
>
> --
> Jens Axboe
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/
--
Jens Axboe
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2009-01-30 11:51 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2009-01-28 6:05 [PATCH v2][RESEND] Allow RT requests to pre-empt ongoing BE timeslice in CFQ Divyesh Shah
2009-01-28 6:17 ` Divyesh Shah
2009-01-30 11:26 ` Jens Axboe
2009-01-30 11:49 ` Jens Axboe
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).