linux-kernel - RE: [PATCH v7 1/3] mmc: core: Add packed command feature of eMMC4.5

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Date:	Tue, 12 Jun 2012 12:15:21 -0700 (PDT)
From:	merez@...eaurora.org
To:	"Seungwon Jeon" <tgih.jun@...sung.com>
Cc:	"'S, Venkatraman'" <svenkatr@...com>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org, "'Chris Ball'" <cjb@...top.org>,
	"'Maya Erez'" <merez@...eaurora.org>,
	"'Subhash Jadavani'" <subhashj@...eaurora.org>
Subject: RE: [PATCH v7 1/3] mmc: core: Add packed command feature of eMMC4.5


> S, Venkatraman <svenkatr@...com> wrote:
>> On Mon, Jun 11, 2012 at 1:53 PM, Seungwon Jeon <tgih.jun@...sung.com>
>> wrote:
>> > This patch adds packed command feature of eMMC4.5.
>> > The maximum number for packing read(or write) is offered
>> > and exception event relevant to packed command which is
>> > used for error handling is enabled. If host wants to use
>> > this feature, MMC_CAP2_PACKED_CMD should be set.
>> >
>> > Signed-off-by: Seungwon Jeon <tgih.jun@...sung.com>
>>
>> Can you please post some clear performance benchmarks with your patchset
>> ?
>> Given that #merez claims to see a significant performance drop for
>> reads, it will be
>> good to compare notes.
>> If it's not too much trouble, both CFQ and deadline scheduler figures
>> would be useful, on a
>> set of read only, write only and parallel read write usecases.
>>
>> I can also try to replicate your results if you can publish the exact
>> configuration you used
>> for testing (example: iozone parameters)
> I'm checking the merez's result.
> Currently packed command is effective on write.
> When running packed write with iozone, there is 25% performance gains.
> (ex: iozone -az -i0 -I -s 10m -f /target/test -e)
>
Our tests shows performance gain of 50-60% in scenarios of only write lmdd
operations.

As I mentioned in the write packing control thread the degradation of read
performance in case of mix read/write operations appears also without
write packing. Therefore I don't think it should stop us from approving
the write packing patch, that gives a significant improvement to the write
performance.
The read performance degradation should be resolved regardless of the
write packing patch.

Thanks,
Maya Erez
--
Sent by consultant of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum

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