From: Jeff Moyer <jmoyer@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>,
linux-kernel@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"J. Bruce Fields" <bfields@fieldses.org>,
"Theodore Ts'o" <tytso@mit.edu>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Dan Williams <dan.j.williams@intel.com>,
Ingo Molnar <mingo@redhat.com>, Jan Kara <jack@suse.com>,
Jeff Layton <jlayton@poochiereds.net>,
Matthew Wilcox <willy@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-nvdimm@ml01.01.org, x86@kernel.org,
xfs@oss.sgi.com, Andrew Morton <akpm@linux-foundation.org>,
Matthew Wilcox <matthew.r.wilcox@intel.com>
Subject: Re: [RFC 00/11] DAX fsynx/msync support
Date: Mon, 02 Nov 2015 09:22:15 -0500 [thread overview]
Message-ID: <x49vb9kqy5k.fsf@segfault.boston.devel.redhat.com> (raw)
In-Reply-To: <20151101232948.GF10656@dastard> (Dave Chinner's message of "Mon, 2 Nov 2015 10:29:48 +1100")
Dave Chinner <david@fromorbit.com> writes:
> Further, REQ_FLUSH/REQ_FUA are more than just "put the data on stable
> storage" commands. They are also IO barriers that affect scheduling
> of IOs in progress and in the request queues. A REQ_FLUSH/REQ_FUA
> IO cannot be dispatched before all prior IO has been dispatched and
> drained from the request queue, and IO submitted after a queued
> REQ_FLUSH/REQ_FUA cannot be scheduled ahead of the queued
> REQ_FLUSH/REQ_FUA operation.
>
> IOWs, REQ_FUA/REQ_FLUSH not only guarantee data is on stable
> storage, they also guarantee the order of IO dispatch and
> completion when concurrent IO is in progress.
This hasn't been the case for several years, now. It used to work that
way, and that was deemed a big performance problem. Since file systems
already issued and waited for all I/O before sending down a barrier, we
decided to get rid of the I/O ordering pieces of barriers (and stop
calling them barriers).
See commit 28e7d184521 (block: drop barrier ordering by queue draining).
Cheers,
Jeff
next prev parent reply other threads:[~2015-11-02 14:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-29 20:12 [RFC 00/11] DAX fsynx/msync support Ross Zwisler
2015-10-29 20:12 ` [RFC 01/11] pmem: add wb_cache_pmem() to the PMEM API Ross Zwisler
2015-10-29 20:12 ` [RFC 02/11] mm: add pmd_mkclean() Ross Zwisler
2015-10-29 20:12 ` [RFC 03/11] pmem: enable REQ_FLUSH handling Ross Zwisler
2015-10-29 20:12 ` [RFC 04/11] dax: support dirty DAX entries in radix tree Ross Zwisler
2015-10-29 20:12 ` [RFC 05/11] mm: add follow_pte_pmd() Ross Zwisler
2015-10-29 20:12 ` [RFC 06/11] mm: add pgoff_mkclean() Ross Zwisler
2015-10-29 20:12 ` [RFC 07/11] mm: add find_get_entries_tag() Ross Zwisler
2015-10-29 20:12 ` [RFC 08/11] fs: add get_block() to struct inode_operations Ross Zwisler
2015-10-29 20:12 ` [RFC 09/11] dax: add support for fsync/sync Ross Zwisler
2015-10-29 20:12 ` [RFC 10/11] xfs, ext2: call dax_pfn_mkwrite() on write fault Ross Zwisler
2015-10-29 20:12 ` [RFC 11/11] ext4: add ext4_dax_pfn_mkwrite() Ross Zwisler
2015-10-29 22:49 ` [RFC 00/11] DAX fsynx/msync support Ross Zwisler
2015-10-30 3:55 ` Dave Chinner
2015-10-30 18:39 ` Ross Zwisler
2015-11-01 23:29 ` Dave Chinner
2015-11-02 14:22 ` Jeff Moyer [this message]
2015-11-02 20:10 ` Dave Chinner
2015-11-02 21:02 ` Jeff Moyer
2015-11-04 18:34 ` Jeff Moyer
2015-11-05 8:33 ` Dave Chinner
2015-11-05 19:49 ` Jeff Moyer
2015-11-05 20:54 ` Jens Axboe
2015-10-30 18:34 ` Dan Williams
2015-10-30 19:43 ` Ross Zwisler
2015-10-30 19:51 ` Dan Williams
2015-11-01 23:36 ` Dave Chinner
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