From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Tom Yan <tom.ty89@gmail.com>
Cc: Shaun Tancheff <shaun.tancheff@seagate.com>,
Shaun Tancheff <shaun@tancheff.com>,
linux-ide@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>, Tejun Heo <tj@kernel.org>,
Josh Bingaman <josh.bingaman@seagate.com>
Subject: Re: [PATCH v5 2/2] Add support for SCT Write Same
Date: Wed, 10 Aug 2016 21:47:40 -0400 [thread overview]
Message-ID: <yq1lh04rs8z.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <CAGnHSE=EnhLwzfuu4wY=WbsA4PJ5tNfwBqErjLL10ea8d3EiGg@mail.gmail.com> (Tom Yan's message of "Wed, 10 Aug 2016 16:50:50 +0000")
>>>>> "Tom" == Tom Yan <tom.ty89@gmail.com> writes:
Tom> Well that is actually the minimum. Modern SSDs often support more
Tom> than one-block payload (e.g. 8, 16...). It's just our SCSI disk
Tom> driver statically limit it to the minimum. Though it allows only
Tom> 0xffffffff / 512 = 8388607 (SD_MAX_WS16_BLOCKS) blocks per WRITE
Tom> SAME (16) command anyway,
Yes, because that's the biggest command we can express in the block
layer.
Tom> so we can at most allow only a 2-block (well, or 3-block) payload.
We tried turning on multi block payloads and it was a massive disaster.
Many drives reported that they supported 8 block payloads but actually
didn't. Instead of playing the blacklist game we capped it at a single
sector.
Many drives from different vendors were affected by this. So we'd have
to make multi block payloads an explicit opt-in like we did for
discard_zeroes_data. However, given that "big" discards are mainly done
synchronously when creating filesystems, I am not sure there is any real
benefit to this.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2016-08-11 1:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-10 1:00 [PATCH v5 0/2] Add support for SCT Write Same Shaun Tancheff
2016-08-10 1:00 ` [PATCH v5 1/2] Use kmap_atomic when rewriting attached page Shaun Tancheff
2016-08-10 10:56 ` Tom Yan
2016-08-10 12:26 ` Shaun Tancheff
2016-08-11 14:13 ` Christoph Hellwig
2016-08-10 1:00 ` [PATCH v5 2/2] Add support for SCT Write Same Shaun Tancheff
2016-08-10 6:31 ` Tom Yan
2016-08-10 11:30 ` Tom Yan
2016-08-10 14:34 ` Shaun Tancheff
2016-08-10 16:50 ` Tom Yan
2016-08-10 18:29 ` Shaun Tancheff
2016-08-11 8:04 ` Tom Yan
2016-08-11 1:47 ` Martin K. Petersen [this message]
2016-08-11 8:46 ` Tom Yan
2016-08-12 1:18 ` Martin K. Petersen
2016-08-11 1:33 ` Martin K. Petersen
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