Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling

From	Dan Williams <dan.j.williams@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling
Date	2015-11-16 21:40 +0100
Message-ID	<qvyJc-3Ft-15@gated-at.bofh.it> (permalink)
References	(4 earlier) <quyUV-6kv-1@gated-at.bofh.it> <qvsaK-7Us-27@gated-at.bofh.it> <qvsNr-8o3-7@gated-at.bofh.it> <qvvLk-1Mp-23@gated-at.bofh.it> <qvxWO-36X-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Nov 16, 2015 at 11:48 AM, Ross Zwisler
<ross.zwisler@linux.intel.com> wrote:
> On Mon, Nov 16, 2015 at 09:28:59AM -0800, Dan Williams wrote:
>> On Mon, Nov 16, 2015 at 6:05 AM, Jan Kara <jack@suse.cz> wrote:
>> > On Mon 16-11-15 14:37:14, Jan Kara wrote:
[..]
> Is there any reason why this wouldn't work or wouldn't be a good idea?

We don't have numbers to support the claim that pcommit is so
expensive as to need be deferred, especially if the upper layers are
already taking the hit on doing the flushes.

REQ_FLUSH, means flush your volatile write cache.  Currently all I/O
through the driver never hits a volatile cache so there's no need to
tell the block layer that we have a volatile write cache, especially
when you have the core mm taking responsibility for doing cache
maintenance for dax-mmap ranges.

We also don't have numbers on if/when wbinvd is a more performant solution.

tl;dr Now that we have a baseline implementation can we please use
data to make future arch decisions?
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Thread

Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Jan Kara <jack@suse.cz> - 2015-11-16 14:40 +0100
  Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Jan Kara <jack@suse.cz> - 2015-11-16 15:20 +0100
    Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Dan Williams <dan.j.williams@intel.com> - 2015-11-16 18:30 +0100
      Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-16 20:50 +0100
        Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Dan Williams <dan.j.williams@intel.com> - 2015-11-16 21:40 +0100
          Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-17 01:00 +0100
    Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Dave Chinner <david@fromorbit.com> - 2015-11-16 23:20 +0100
      Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-11-17 00:30 +0100
        Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling Dave Chinner <david@fromorbit.com> - 2015-11-17 00:50 +0100

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