From: Dan Williams <dan.j.williams@intel.com>
To: Jon Derrick <jonathan.derrick@intel.com>
Cc: linux-block@vger.kernel.org, Jens Axboe <axboe@fb.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Jeff Moyer <jmoyer@redhat.com>,
Stephen Bates <stephen.bates@microsemi.com>,
Keith Busch <keith.busch@intel.com>,
linux-nvme@lists.infradead.org,
Christoph Hellwig <hch@infradead.org>,
"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [RFCv2 3/3] block: Introduce S_HIPRI inode flag
Date: Sat, 14 May 2016 07:22:29 -0700 [thread overview]
Message-ID: <CAPcyv4ibBEh7xm8jUX-aq0a2ecqbZugDa_L1K=dbFujbKaDVVw@mail.gmail.com> (raw)
In-Reply-To: <1463184168-3381-4-git-send-email-jonathan.derrick@intel.com>
[ adding Martin, given his hint infrastructure that is in the works... ]
On Fri, May 13, 2016 at 5:02 PM, Jon Derrick <jonathan.derrick@intel.com> wrote:
> S_HIPRI is a hint that indicates the file (currently only block devices)
> is a high priority file. This hint allows direct-io to the block device
> to poll for completions if polling is available to the block device.
>
> The motivation for this patch comes from tiered caching solutions. A
> user may wish to have low-latency block devices act as a cache for
> higher-latency storage media.
>
> With the introduction of block polling, polling could be enabled on a
> queue of a block device. The preadv2/pwritev2 sets allowed a user to
> specify per-io polling, but removed the ability to poll per-queue.
>
> Instead of having a user modify their software to use preadv2/pwritev2,
> this patch allows a user to set S_HIPRI on a block device file to request
> all direct-io for this file to be polled.
Setting aside whether this should be a per-task ioprio hint vs a block
device inode hint, this single flag loses the granularity of whether
reads or writes are polled. Low latency reads with posted writes
seems a valid configuration.
prev parent reply other threads:[~2016-05-14 14:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-14 0:02 [RFCv2 0/3] Support for high-priority block device flag Jon Derrick
2016-05-14 0:02 ` [RFCv2 1/3] block: allow other bd i_node flags when DAX is disabled Jon Derrick
2016-05-14 0:02 ` [RFCv2 2/3] block: add helper for setting and clearing S_DAX on inode Jon Derrick
2016-05-14 5:05 ` Elliott, Robert (Persistent Memory)
2016-05-16 17:31 ` Jon Derrick
2016-05-14 0:02 ` [RFCv2 3/3] block: Introduce S_HIPRI inode flag Jon Derrick
2016-05-14 14:22 ` Dan Williams [this message]
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