From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Tom Yan <tom.ty89@gmail.com>
Cc: linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org
Subject: Re: configurable discard parameters
Date: Sat, 20 Jun 2015 20:20:54 -0400 [thread overview]
Message-ID: <yq1fv5l9ajd.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <CAGnHSEmDQ6xaJsw9i=v23BffWQ8RncrgNBsGWy3ziC36QK+9yQ@mail.gmail.com> (Tom Yan's message of "Sun, 21 Jun 2015 01:12:10 +0800")
>>>>> "Tom" == Tom Yan <tom.ty89@gmail.com> writes:
Tom> Today I check if blkdiscard really does a full device trim/wipe for
Tom> my Intel 530 SSD (240gb) with hexdump. I end up found that it fail
Tom> to do so because it report garbage info on its block limits VPD.
It is a SATA-attached drive, it has no block limits VPD. What you are
seeing is information prepared by libata's SATL.
Tom> The fact is, in each iteration, for this drive, blkdiscard can only
Tom> trim a maximum of 65528 sectors, which is the largest multiple of 8
Tom> sectors, which is the minimum possible.
Maximum write same length: 0x3fffc0 blocks
That's 2GB-e per request for a drive with 512-byte logical blocks.
Tom> but still I would like to know why the kernel doesn't allow
Tom> "discard_granularity" and "discard_max_bytes" to be configurable
Tom> for users.
Because if the vendor got these trivial values wrong there is little to
no chance that they implemented discard correctly in their firmware.
--
Martin K. Petersen Oracle Linux Engineering
--
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next prev parent reply other threads:[~2015-06-21 0:20 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-20 17:12 configurable discard parameters Tom Yan
2015-06-21 0:20 ` Martin K. Petersen [this message]
2015-06-21 7:03 ` Tom Yan
2015-06-21 8:05 ` Tom Yan
2015-06-21 12:36 ` Tom Yan
2015-06-21 20:30 ` Tom Yan
2015-06-22 20:57 ` Martin K. Petersen
2015-06-23 14:16 ` Tom Yan
2015-06-23 15:36 ` Martin K. Petersen
2015-06-23 16:41 ` Tom Yan
2015-06-23 17:03 ` Martin K. Petersen
2015-06-23 17:24 ` Tom Yan
2015-06-23 18:26 ` Martin K. Petersen
2015-06-23 21:25 ` Tom Yan
2015-06-24 2:55 ` Martin K. Petersen
2015-06-24 12:46 ` Tom Yan
2015-06-25 1:15 ` Martin K. Petersen
2015-06-26 7:05 ` Tom Yan
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