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From: Nikhilesh Reddy <reddyn@codeaurora.org>
To: Theodore Ts'o <tytso@mit.edu>, linux-ext4@vger.kernel.org
Subject: Using Cache barriers in lieu of REQ_FLUSH | REQ_FUA for emmc 5.1 (jdec spec JESD84-B51)
Date: Tue, 15 Sep 2015 16:17:46 -0700	[thread overview]
Message-ID: <55F8A71A.3030001@codeaurora.org> (raw)

Hi

The eMMC 5.1 spec defines cache "barrier" capability of the eMMC device 
as defined in JESD84-B51

I was wondering if there were any downsides to replacing the 
WRITE_FLUSH_FUA	 with the cache barrier?

I understand that REQ_FLUSH is used to ensure that the current cache be 
flushed to prevent any reordering but I dont seem to be clear on why
REQ_FUA is used.
Can someone please help me understand this part?

But as far as I understand it ... the cache barriers can be used to 
replace all the flush requests.

Please let me know if there is any downside to this ?

I know there there was a big decision in 2010 
https://lwn.net/Articles/400541/
and http://lwn.net/Articles/399148/
to remove the software based barrier support... but with the hardware 
supporting "barriers" is there a downside to using them to replace the 
flushes?
-- 
Thanks
Nikhilesh Reddy

Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

             reply	other threads:[~2015-09-15 23:17 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-15 23:17 Nikhilesh Reddy [this message]
2015-09-20  3:42 ` Using Cache barriers in lieu of REQ_FLUSH | REQ_FUA for emmc 5.1 (jdec spec JESD84-B51) Theodore Ts'o
2015-09-28 22:28   ` Nikhilesh Reddy
2015-10-23  6:33   ` Running XFS tests on qemu Nikhilesh Reddy
2015-10-23  9:34     ` Theodore Ts'o
2015-10-27 17:55       ` Nikhilesh Reddy

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