On Mon, 19 Sep 2016, Peter Zijlstra wrote:
> On Tue, Sep 13, 2016 at 09:39:59AM -0400, Mike Snitzer wrote:
> > So I'm not sure how this dm-bufio local cond_resched() wrapper still got
> > in... happy to take your patch.
> >
> > Please respond with whatever SOB you'd like applied to the patch header.
>
> Sorry, for the delay, here goes.
Why not change it to might_sleep()? - that would be almost equivalent to
the code that was there before (i.e. reschedule only if
CONFIG_PREEMPT_VOLUNTARY is set).
If we call the cond_resched() function in tight loops such as walking all
buffers in a list, there may be performance penalty due to the call, so
the call should be done only if it is really needed (i.e. in
CONFIG_PREEMPT_VOLUNTARY case).
Mikulas
> ---
> Subject: dm: Remove dm_bufio_cond_resched()
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Tue, 13 Sep 2016 10:45:20 +0200
>
> Remove pointless local wrappery. Use cond_resched() like everybody else.
>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> Cc: Alasdair Kergon <agk@xxxxxxxxxx>
> Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
> drivers/md/dm-bufio.c | 31 +++++++++----------------------
> 1 file changed, 9 insertions(+), 22 deletions(-)
>
> --- a/drivers/md/dm-bufio.c
> +++ b/drivers/md/dm-bufio.c
> @@ -191,19 +191,6 @@ static void dm_bufio_unlock(struct dm_bu
> mutex_unlock(&c->lock);
> }
>
> -/*
> - * FIXME Move to sched.h?
> - */
> -#ifdef CONFIG_PREEMPT_VOLUNTARY
> -# define dm_bufio_cond_resched() \
> -do { \
> - if (unlikely(need_resched())) \
> - _cond_resched(); \
> -} while (0)
> -#else
> -# define dm_bufio_cond_resched() do { } while (0)
> -#endif
> -
> /*----------------------------------------------------------------*/
>
> /*
> @@ -741,7 +728,7 @@ static void __flush_write_list(struct li
> list_entry(write_list->next, struct dm_buffer, write_list);
> list_del(&b->write_list);
> submit_io(b, WRITE, b->block, write_endio);
> - dm_bufio_cond_resched();
> + cond_resched();
> }
> blk_finish_plug(&plug);
> }
> @@ -780,7 +767,7 @@ static struct dm_buffer *__get_unclaimed
> __unlink_buffer(b);
> return b;
> }
> - dm_bufio_cond_resched();
> + cond_resched();
> }
>
> list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
> @@ -791,7 +778,7 @@ static struct dm_buffer *__get_unclaimed
> __unlink_buffer(b);
> return b;
> }
> - dm_bufio_cond_resched();
> + cond_resched();
> }
>
> return NULL;
> @@ -923,7 +910,7 @@ static void __write_dirty_buffers_async(
> return;
>
> __write_dirty_buffer(b, write_list);
> - dm_bufio_cond_resched();
> + cond_resched();
> }
> }
>
> @@ -973,7 +960,7 @@ static void __check_watermark(struct dm_
> return;
>
> __free_buffer_wake(b);
> - dm_bufio_cond_resched();
> + cond_resched();
> }
>
> if (c->n_buffers[LIST_DIRTY] > threshold_buffers)
> @@ -1170,7 +1157,7 @@ void dm_bufio_prefetch(struct dm_bufio_c
> submit_io(b, READ, b->block, read_endio);
> dm_bufio_release(b);
>
> - dm_bufio_cond_resched();
> + cond_resched();
>
> if (!n_blocks)
> goto flush_plug;
> @@ -1291,7 +1278,7 @@ int dm_bufio_write_dirty_buffers(struct
> !test_bit(B_WRITING, &b->state))
> __relink_lru(b, LIST_CLEAN);
>
> - dm_bufio_cond_resched();
> + cond_resched();
>
> /*
> * If we dropped the lock, the list is no longer consistent,
> @@ -1574,7 +1561,7 @@ static unsigned long __scan(struct dm_bu
> freed++;
> if (!--nr_to_scan || ((count - freed) <= retain_target))
> return freed;
> - dm_bufio_cond_resched();
> + cond_resched();
> }
> }
> return freed;
> @@ -1808,7 +1795,7 @@ static void __evict_old_buffers(struct d
> if (__try_evict_buffer(b, 0))
> count--;
>
> - dm_bufio_cond_resched();
> + cond_resched();
> }
>
> dm_bufio_unlock(c);
>
--
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