From: willy@linux.intel.com (Matthew Wilcox)
Subject: Cmd - comp write
Date: Thu, 24 Apr 2014 09:58:05 -0400 [thread overview]
Message-ID: <20140424135805.GA5886@linux.intel.com> (raw)
In-Reply-To: <7212DDF9-6821-4D7E-BD4D-655031AD03F7@gmail.com>
On Wed, Apr 23, 2014@08:37:39PM -0700, Learner wrote:
> Hello
>
> How frequently is Fused command - compare-write used?
> Is it for avoiding writes for SSDs if thee is no change? Ie read and compare the block to be written and don't write if there is no change..
Compare-and-Write is a building block for an (unspecified, advisory)
locking protocol. If two entities wish to gain exclusive access to a
range of LBAs, they can agree on a block to use as their lock, and agree
on a bit-pattern to be found in that block to indicate 'unlocked'.
If anyone is using it, they're doing so through ioctls; there's no way
to submit a BIO that maps to a compare-and-write.
next prev parent reply other threads:[~2014-04-24 13:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-24 3:37 Cmd - comp write Learner
2014-04-24 9:50 ` Ebrahim Hashemi
2014-04-24 13:58 ` Matthew Wilcox [this message]
2014-04-24 17:03 ` Learner Study
2014-04-24 17:43 ` Matthew Wilcox
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