| Message ID | 3578876466-3733-1-git-send-email-nj.shetty@samsung.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
On 05/29/83 20:21, Nitesh Shetty wrote:
> [ ... ]
Hello Nitesh,
Can you check the clock of the system you used to send this e-mail? In
the header of your e-mail I found the following:
Date: Sun, 30 May 2083 09:51:06 +0530
Thanks,
Bart.
On Sun, May 30, 2083 at 09:51:06AM +0530, Nitesh Shetty wrote: > This removes the dependency on interrupts to wake up task. Set task > state as TASK_RUNNING, if need_resched() returns true, > while polling for IO completion. > Earlier, polling task used to sleep, relying on interrupt to wake it up. > This made some IO take very long when interrupt-coalescing is enabled in > NVMe. This is a horrible Changelog.. it does not in fact explain why the patch works or is correct. Also, set_current_state(TASK_RUNNING) is dodgy (similarly in __blk_mq_poll), why do you need that memory barrier? > Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com> > --- > fs/block_dev.c | 16 ++++++++++++---- > fs/direct-io.c | 8 ++++++-- > fs/iomap.c | 10 +++++++--- > 3 files changed, 25 insertions(+), 9 deletions(-) > > diff --git a/fs/block_dev.c b/fs/block_dev.c > index 4a181fc..a87d8b7 100644 > --- a/fs/block_dev.c > +++ b/fs/block_dev.c > @@ -236,9 +236,13 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter, > set_current_state(TASK_UNINTERRUPTIBLE); > if (!READ_ONCE(bio.bi_private)) > break; > - if (!(iocb->ki_flags & IOCB_HIPRI) || > - !blk_poll(bdev_get_queue(bdev), qc)) > + if (!(iocb->ki_flags & IOCB_HIPRI)) > io_schedule(); > + else if (!blk_poll(bdev_get_queue(bdev), qc)) { > + if (need_resched()) > + set_current_state(TASK_RUNNING); > + io_schedule(); > + } > } > __set_current_state(TASK_RUNNING); >
On Tue, Feb 20, 2018 at 02:21:37PM +0100, Peter Zijlstra wrote: > Also, set_current_state(TASK_RUNNING) is dodgy (similarly in > __blk_mq_poll), why do you need that memory barrier? You're right. The subsequent revision that was committed removed the barrier. The commit is here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=67b4110f8c8d16e588d7730db8e8b01b32c1bd8b I hope the code at least looks more reasonable. The changelog isn't much different, though.
On 2/20/18 3:21 AM, Peter Zijlstra wrote: > On Sun, May 30, 2083 at 09:51:06AM +0530, Nitesh Shetty wrote: >> This removes the dependency on interrupts to wake up task. Set task >> state as TASK_RUNNING, if need_resched() returns true, >> while polling for IO completion. >> Earlier, polling task used to sleep, relying on interrupt to wake it up. >> This made some IO take very long when interrupt-coalescing is enabled in >> NVMe. > > This is a horrible Changelog.. it does not in fact explain why the patch > works or is correct. Yeah, that should have been improved. > Also, set_current_state(TASK_RUNNING) is dodgy (similarly in > __blk_mq_poll), why do you need that memory barrier? I pointed that out in the review, and v2 fixed it. v2 is the one that got merged.
On Tue, Feb 20, 2018 at 12:37:07PM -1000, Jens Axboe wrote: > On 2/20/18 3:21 AM, Peter Zijlstra wrote: > > On Sun, May 30, 2083 at 09:51:06AM +0530, Nitesh Shetty wrote: > >> This removes the dependency on interrupts to wake up task. Set task > >> state as TASK_RUNNING, if need_resched() returns true, > >> while polling for IO completion. > >> Earlier, polling task used to sleep, relying on interrupt to wake it up. > >> This made some IO take very long when interrupt-coalescing is enabled in > >> NVMe. > > > > This is a horrible Changelog.. it does not in fact explain why the patch > > works or is correct. > > Yeah, that should have been improved. Being ever more forgetful (I blame the kids) I find Changelogs more and more important, ymmv ;-) > > Also, set_current_state(TASK_RUNNING) is dodgy (similarly in > > __blk_mq_poll), why do you need that memory barrier? > > I pointed that out in the review, and v2 fixed it. v2 is the > one that got merged. Right missed that. In fact, possibly the only reason I saw this is that Nitesh had this computer configured wrong and the email is from the future and thus the very first entry in my lkml folder.
On 05/29/2083 08:21 PM, Nitesh Shetty wrote: > This removes the dependency on interrupts to wake up task. Set task > state as TASK_RUNNING, if need_resched() returns true, > while polling for IO completion. > Earlier, polling task used to sleep, relying on interrupt to wake it up. > This made some IO take very long when interrupt-coalescing is enabled in > NVMe. > > Reference: > http://lists.infradead.org/pipermail/linux-nvme/2018-February/015435.html > Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com> There is something seriously wrong with the date on your computer, this patch is dated from May 29th 2083,... I would not be surprised if it messed up people's email client and you did not get any response because of that...
diff --git a/fs/block_dev.c b/fs/block_dev.c index 4a181fc..a87d8b7 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -236,9 +236,13 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter, set_current_state(TASK_UNINTERRUPTIBLE); if (!READ_ONCE(bio.bi_private)) break; - if (!(iocb->ki_flags & IOCB_HIPRI) || - !blk_poll(bdev_get_queue(bdev), qc)) + if (!(iocb->ki_flags & IOCB_HIPRI)) io_schedule(); + else if (!blk_poll(bdev_get_queue(bdev), qc)) { + if (need_resched()) + set_current_state(TASK_RUNNING); + io_schedule(); + } } __set_current_state(TASK_RUNNING); @@ -401,9 +405,13 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages) if (!READ_ONCE(dio->waiter)) break; - if (!(iocb->ki_flags & IOCB_HIPRI) || - !blk_poll(bdev_get_queue(bdev), qc)) + if (!(iocb->ki_flags & IOCB_HIPRI)) io_schedule(); + else if (!blk_poll(bdev_get_queue(bdev), qc)) { + if (need_resched()) + set_current_state(TASK_RUNNING); + io_schedule(); + } } __set_current_state(TASK_RUNNING); diff --git a/fs/direct-io.c b/fs/direct-io.c index a0ca9e4..c815ac9 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -518,9 +518,13 @@ static struct bio *dio_await_one(struct dio *dio) __set_current_state(TASK_UNINTERRUPTIBLE); dio->waiter = current; spin_unlock_irqrestore(&dio->bio_lock, flags); - if (!(dio->iocb->ki_flags & IOCB_HIPRI) || - !blk_poll(dio->bio_disk->queue, dio->bio_cookie)) + if (!(dio->iocb->ki_flags & IOCB_HIPRI)) io_schedule(); + else if (!blk_poll(dio->bio_disk->queue, dio->bio_cookie)) { + if (need_resched()) + __set_current_state(TASK_RUNNING); + io_schedule(); + } /* wake up sets us TASK_RUNNING */ spin_lock_irqsave(&dio->bio_lock, flags); dio->waiter = NULL; diff --git a/fs/iomap.c b/fs/iomap.c index afd1635..b51569d 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -1072,10 +1072,14 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, break; if (!(iocb->ki_flags & IOCB_HIPRI) || - !dio->submit.last_queue || - !blk_poll(dio->submit.last_queue, - dio->submit.cookie)) + !dio->submit.last_queue) io_schedule(); + else if (!blk_poll(dio->submit.last_queue, + dio->submit.cookie)) { + if (need_resched()) + set_current_state(TASK_RUNNING); + io_schedule(); + } } __set_current_state(TASK_RUNNING); }
This removes the dependency on interrupts to wake up task. Set task state as TASK_RUNNING, if need_resched() returns true, while polling for IO completion. Earlier, polling task used to sleep, relying on interrupt to wake it up. This made some IO take very long when interrupt-coalescing is enabled in NVMe. Reference: http://lists.infradead.org/pipermail/linux-nvme/2018-February/015435.html Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com> --- fs/block_dev.c | 16 ++++++++++++---- fs/direct-io.c | 8 ++++++-- fs/iomap.c | 10 +++++++--- 3 files changed, 25 insertions(+), 9 deletions(-)