Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks

From	Ric Wheeler <rwheeler@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks
Date	2016-03-17 14:50 +0100
Message-ID	<rdGtj-844-5@gated-at.bofh.it> (permalink)
References	(6 earlier) <rd72x-M3-11@gated-at.bofh.it> <rd7ce-15y-9@gated-at.bofh.it> <rd7Ff-1gK-1@gated-at.bofh.it> <rd7YC-1nQ-15@gated-at.bofh.it> <rds6Z-6Wr-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 03/16/2016 06:23 PM, Chris Mason wrote:
> On Tue, Mar 15, 2016 at 05:51:17PM -0700, Chris Mason wrote:
>> On Tue, Mar 15, 2016 at 07:30:14PM -0500, Eric Sandeen wrote:
>>> On 3/15/16 7:06 PM, Linus Torvalds wrote:
>>>> On Tue, Mar 15, 2016 at 4:52 PM, Dave Chinner <david@fromorbit.com> wrote:
>>>>>> It is pretty clear that the onus is on the patch submitter to
>>>>>> provide justification for inclusion, not for the reviewer/Maintainer
>>>>>> to have to prove that the solution is unworkable.
>>>> I agree, but quite frankly, performance is a good justification.
>>>>
>>>> So if Ted can give performance numbers, that's justification enough.
>>>> We've certainly taken changes with less.
>>> I've been away from ext4 for a while, so I'm really not on top of the
>>> mechanics of the underlying problem at the moment.
>>>
>>> But I would say that in addition to numbers showing that ext4 has trouble
>>> with unwritten extent conversion, we should have an explanation of
>>> why it can't be solved in a way that doesn't open up these concerns.
>>>
>>> XFS certainly has different mechanisms, but is the demonstrated workload
>>> problematic on XFS (or btrfs) as well?  If not, can ext4 adopt any of the
>>> solutions that make the workload perform better on other filesystems?
>> When I've benchmarked this in the past, doing small random buffered writes
>> into an preallocated extent was dramatically (3x or more) slower on xfs
>> than doing them into a fully written extent.  That was two years ago,
>> but I can redo it.
> So I re-ran some benchmarks, with 4K O_DIRECT random ios on nvme (4.5
> kernel).  This is O_DIRECT without O_SYNC.  I don't think xfs will do
> commits for each IO into the prealloc file?  O_SYNC makes it much
> slower, so hopefully I've got this right.
>
> The test runs for 60 seconds, and I used an iodepth of 4:
>
> prealloc file: 32,000 iops
> overwrite:    121,000 iops
>
> If I bump the iodepth up to 512:
>
> prealloc file: 33,000 iops
> overwrite:   279,000 iops
>
> For streaming writes, XFS converts prealloc to written much better when
> the IO isn't random.  You can start seeing the difference at 16K
> sequential O_DIRECT writes, but really its not a huge impact.  The worst
> case is 4K:
>
> prealloc file: 227MB/s
> overwrite:     340MB/s
>
> I can't think of sequential workloads where this will matter, since they
> will either end up with bigger IO or the performance impact won't get
> noticed.
>
> -chris

I think that these numbers are the interesting ones, see a 4x slow down is 
certainly significant.

If you do the same patch after hacking XFS preallocation as Dave suggested with 
xfs_db, do we get most of the performance back?

Ric

Thread

Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Gregory Farnum <greg@gregs42.com> - 2016-03-09 23:30 +0100
  Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-10 00:10 +0100
    Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <ricwheeler@gmail.com> - 2016-03-10 16:00 +0100
      Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-10 19:40 +0100
        Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-10 22:50 +0100
        Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-11 05:50 +0100
          Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range  of blocks One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-03-11 15:10 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-11 16:30 +0100
            Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-11 18:30 +0100
              Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Andy Lutomirski <luto@amacapital.net> - 2016-03-11 18:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-11 19:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-11 23:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-12 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-12 01:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-12 08:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Thomas Schoebel-Theuer <tst@schoebel-theuer.de> - 2016-03-12 11:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-14 00:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-14 11:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-14 15:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-15 21:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-15 21:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-15 22:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-15 23:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-16 00:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-16 03:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Andreas Dilger <adilger@dilger.ca> - 2016-03-16 22:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-17 01:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Eric Sandeen <esandeen@redhat.com> - 2016-03-17 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-17 02:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Gregory Farnum <greg@gregs42.com> - 2016-03-17 06:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-17 13:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-17 18:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-17 19:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-17 19:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Chris Mason <clm@fb.com> - 2016-03-17 19:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Andreas Dilger <adilger@dilger.ca> - 2016-03-17 21:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Chris Mason <clm@fb.com> - 2016-03-17 22:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Theodore Ts'o <tytso@mit.edu> - 2016-03-18 04:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Jeff Moyer <jmoyer@redhat.com> - 2016-03-18 16:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks "Martin K. Petersen" <martin.petersen@oracle.com> - 2016-03-18 21:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Gregory Farnum <greg@gregs42.com> - 2016-03-18 08:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-18 08:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-17 02:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-03-17 03:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks NeilBrown <neilb@suse.com> - 2016-03-19 00:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-16 00:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-16 00:20 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-16 01:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Dave Chinner <david@fromorbit.com> - 2016-03-16 01:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-16 01:10 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Eric Sandeen <esandeen@redhat.com> - 2016-03-16 01:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Chris Mason <clm@fb.com> - 2016-03-16 02:00 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Chris Mason <clm@fb.com> - 2016-03-16 23:30 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Ric Wheeler <rwheeler@redhat.com> - 2016-03-17 14:50 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of  blocks Eric Sandeen <esandeen@redhat.com> - 2016-03-15 23:40 +0100
                Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks Linus Torvalds <torvalds@linux-foundation.org> - 2016-03-12 01:40 +0100

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