2008-11-04 16:16:00

by Alan Stern

Subject: [PATCH 2/2] Block: use round_jiffies_up()

This patch (as1159) changes the timeout routines in the block core to
use round_jiffies_up(). There's no point in rounding the timer
deadline down, since if it expires too early we will have to restart
it.

The patch also removes a redundant test of q->rq_timed_out_fn, and it
sets req->deadline back to 0 when req is removed from the timer list
(to indicate the req is no longer being timed).

Signed-off-by: Alan Stern <[email protected]>

---

Index: usb-2.6/block/blk-timeout.c
===================================================================
--- usb-2.6.orig/block/blk-timeout.c
+++ usb-2.6/block/blk-timeout.c
@@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
/*
* Nothing to detach
*/
- if (!q->rq_timed_out_fn || !req->deadline)
+ if (!req->deadline)
return;

list_del_init(&req->timeout_list);

if (list_empty(&q->timeout_list))
del_timer(&q->timeout);
+ req->deadline = 0;
}

static void blk_rq_timed_out(struct request *req)
@@ -142,7 +143,7 @@ void blk_rq_timed_out_timer(unsigned lon
}

if (next_set && !list_empty(&q->timeout_list))
- mod_timer(&q->timeout, round_jiffies(next));
+ mod_timer(&q->timeout, round_jiffies_up(next));

spin_unlock_irqrestore(q->queue_lock, flags);
}
@@ -201,7 +202,7 @@ void blk_add_timer(struct request *req)
* than an existing one, modify the timer. Round to next nearest
* second.
*/
- expiry = round_jiffies(req->deadline);
+ expiry = round_jiffies_up(req->deadline);

/*
* We use ->deadline == 0 to detect whether a timer was added or

2008-11-05 03:34:58

by Tejun Heo

Subject: Re: [PATCH 2/2] Block: use round_jiffies_up()

Hello,

Alan Stern wrote:
> @@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
> /*
> * Nothing to detach
> */
> - if (!q->rq_timed_out_fn || !req->deadline)
> + if (!req->deadline)
> return;
>
> list_del_init(&req->timeout_list);
>
> if (list_empty(&q->timeout_list))
> del_timer(&q->timeout);
> + req->deadline = 0;
> }

Actually, this can just be

blk_delete_timer()
{
list_del_init(&req->timeout_list);
if (list_empty(&q->timeout_list))
del_timer(&q->timeout);
}

and none of req->deadline trick is necessary.

Thanks.

--
tejun

2008-11-05 16:21:58

by Alan Stern

Subject: Re: [PATCH 2/2] Block: use round_jiffies_up()

On Wed, 5 Nov 2008, Tejun Heo wrote:

> Hello,
>
> Alan Stern wrote:
> > @@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
> > /*
> > * Nothing to detach
> > */
> > - if (!q->rq_timed_out_fn || !req->deadline)
> > + if (!req->deadline)
> > return;
> >
> > list_del_init(&req->timeout_list);
> >
> > if (list_empty(&q->timeout_list))
> > del_timer(&q->timeout);
> > + req->deadline = 0;
> > }
>
> Actually, this can just be
>
> blk_delete_timer()
> {
> list_del_init(&req->timeout_list);
> if (list_empty(&q->timeout_list))
> del_timer(&q->timeout);
> }
>
> and none of req->deadline trick is necessary.

True. And if we do this, then there's no need to test and increment
req->deadline in blk_add_timer().

Alan Stern

2008-11-05 19:13:34

by Jens Axboe

Subject: Re: [PATCH 2/2] Block: use round_jiffies_up()

On Wed, Nov 05 2008, Alan Stern wrote:
> On Wed, 5 Nov 2008, Tejun Heo wrote:
>
> > Hello,
> >
> > Alan Stern wrote:
> > > @@ -78,13 +78,14 @@ void blk_delete_timer(struct request *re
> > > /*
> > > * Nothing to detach
> > > */
> > > - if (!q->rq_timed_out_fn || !req->deadline)
> > > + if (!req->deadline)
> > > return;
> > >
> > > list_del_init(&req->timeout_list);
> > >
> > > if (list_empty(&q->timeout_list))
> > > del_timer(&q->timeout);
> > > + req->deadline = 0;
> > > }
> >
> > Actually, this can just be
> >
> > blk_delete_timer()
> > {
> > list_del_init(&req->timeout_list);
> > if (list_empty(&q->timeout_list))
> > del_timer(&q->timeout);
> > }
> >
> > and none of req->deadline trick is necessary.
>
> True. And if we do this, then there's no need to test and increment
> req->deadline in blk_add_timer().

It was an optimization for drivers that don't use block layer timers,
but we can get rid of it.

--
Jens Axboe

2008-11-05 21:19:44

by Alan Stern

Subject: [PATCH 2/2 ver 2] Block: use round_jiffies_up()

This patch (as1159b) changes the timeout routines in the block core to
use round_jiffies_up(). There's no point in rounding the timer
deadline down, since if it expires too early we will have to restart
it.

The patch also removes some unnecessary tests when a request is
removed from the queue's timer list.

Signed-off-by: Alan Stern <[email protected]>

---

Index: usb-2.6/block/blk-timeout.c
===================================================================
--- usb-2.6.orig/block/blk-timeout.c
+++ usb-2.6/block/blk-timeout.c
@@ -75,14 +75,7 @@ void blk_delete_timer(struct request *re
{
struct request_queue *q = req->q;

- /*
- * Nothing to detach
- */
- if (!q->rq_timed_out_fn || !req->deadline)
- return;
-
list_del_init(&req->timeout_list);
-
if (list_empty(&q->timeout_list))
del_timer(&q->timeout);
}
@@ -142,7 +135,7 @@ void blk_rq_timed_out_timer(unsigned lon
}

if (next_set && !list_empty(&q->timeout_list))
- mod_timer(&q->timeout, round_jiffies(next));
+ mod_timer(&q->timeout, round_jiffies_up(next));

spin_unlock_irqrestore(q->queue_lock, flags);
}
@@ -198,17 +191,10 @@ void blk_add_timer(struct request *req)

/*
* If the timer isn't already pending or this timeout is earlier
- * than an existing one, modify the timer. Round to next nearest
+ * than an existing one, modify the timer. Round up to next nearest
* second.
*/
- expiry = round_jiffies(req->deadline);
-
- /*
- * We use ->deadline == 0 to detect whether a timer was added or
- * not, so just increase to next jiffy for that specific case
- */
- if (unlikely(!req->deadline))
- req->deadline = 1;
+ expiry = round_jiffies_up(req->deadline);

if (!timer_pending(&q->timeout) ||
time_before(expiry, q->timeout.expires))