linux-kernel - Re: Slow dc3dd in 3.18 on x86

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Message-ID: <yq1r3xxtfa7.fsf@sermon.lab.mkp.net>
Date:	Fri, 24 Oct 2014 15:54:08 -0400
From:	"Martin K. Petersen" <martin.petersen@...cle.com>
To:	"Michael L. Semon" <mlsemon35@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: Slow dc3dd in 3.18 on x86

>>>>> "Michael" == Michael L Semon <mlsemon35@...il.com> writes:

Michael> This week, a simple `dc3dd wipe=/dev/sda5` operation had speeds
Michael> cut from 10-15 MB/s down to less than 1.8 MB/s.  With this
Michael> method, syncs took so long that magic SysRq keys were needed to
Michael> stop the PC.  A bisect let me here:

That commit itself doesn't do anything.

I was concerned that somehow integrity got enabled by accident and you
were bogged down by checksum calculations but I see no evidence that
this would be happening. Ran a few tests on ATA systems here.

So I'm puzzled.

Please let me know if the disk has an integrity profile in sysfs.

-- 
Martin K. Petersen	Oracle Linux Engineering
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