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From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Daejun Park <daejun7.park@samsung.com>,
	"avri.altman@wdc.com" <avri.altman@wdc.com>,
	"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"asutoshd@codeaurora.org" <asutoshd@codeaurora.org>,
	"beanhuo@micron.com" <beanhuo@micron.com>,
	"stanley.chu@mediatek.com" <stanley.chu@mediatek.com>,
	"cang@codeaurora.org" <cang@codeaurora.org>,
	"bvanassche@acm.org" <bvanassche@acm.org>,
	"tomas.winkler@intel.com" <tomas.winkler@intel.com>,
	ALIM AKHTAR <alim.akhtar@samsung.com>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Sang-yoon Oh <sangyoon.oh@samsung.com>,
	Sung-Jun Park <sungjun07.park@samsung.com>,
	yongmyung lee <ymhungry.lee@samsung.com>,
	Jinyoung CHOI <j-young.choi@samsung.com>,
	Adel Choi <adel.choi@samsung.com>,
	BoRam Shin <boram.shin@samsung.com>
Subject: Re: [PATCH v6 0/5] scsi: ufs: Add Host Performance Booster Support
Date: Wed, 22 Jul 2020 09:27:07 -0400
Message-ID: <yq1blk7g1jd.fsf@ca-mkp.ca.oracle.com> (raw)
In-Reply-To: <20200722063937.GA21117@infradead.org> (Christoph Hellwig's message of "Wed, 22 Jul 2020 07:39:37 +0100")


Christoph,

> As this monster seesm to come back again and again let me re-iterate
> my statement:
>
> I do not think Linux should support a broken standards extensions that
> creates a huge share state between the Linux initator and the target
> device like this with all its associated problems.

I spent a couple of hours looking at this series again last night. And
while the code has improved, I do remain concerned about the general
concept.

I understand how caching the FTL in host memory can improve performance
from a theoretical perspective. However, I am not sure how much a
difference this is going to make outside of synthetic benchmarks. What
are the workloads that keep reading the same blocks from media? Or does
the performance improvement exclusively come from the second order
pre-fetching effect for larger I/Os? If so, why is the device's internal
L2P SRAM cache ineffective at handling that case?

-- 
Martin K. Petersen	Oracle Linux Engineering

  reply index

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200713103423epcms2p8442ee7cc22395e4a4cedf224f95c45e8@epcms2p8>
2020-07-13 10:34 ` Daejun Park
     [not found]   ` <CGME20200713103423epcms2p8442ee7cc22395e4a4cedf224f95c45e8@epcms2p4>
2020-07-13 10:40     ` [PATCH v6 2/5] scsi: ufs: Add UFS-feature layer Daejun Park
2020-07-22  6:41       ` Christoph Hellwig
2020-07-22 12:46         ` Martin K. Petersen
2020-07-22 15:06           ` Bart Van Assche
2020-07-13 10:53     ` [PATCH v6 4/5] scsi: ufs: L2P map management for HPB read Daejun Park
2020-07-15 18:34   ` [PATCH v6 0/5] scsi: ufs: Add Host Performance Booster Support Avi Shchislowski
2020-07-16  1:41     ` Bart Van Assche
2020-07-16 10:00       ` Avi Shchislowski
2020-07-16 16:21         ` Eric Biggers
2020-07-16 16:45         ` Alim Akhtar
2020-07-17 15:54           ` Avi Shchislowski
2020-08-10 15:38         ` Greg KH
2020-07-16  8:13     ` Bean Huo
2020-07-16  8:14     ` Bean Huo
2020-07-16  1:05   ` Alim Akhtar
2020-07-17  5:24     ` Avri Altman
2020-07-19  6:35       ` Avri Altman
2020-07-21 18:15         ` Alim Akhtar
2020-07-22  4:20         ` Martin K. Petersen
2020-07-22  6:18           ` Avri Altman
2020-07-22  6:39   ` Christoph Hellwig
2020-07-22 13:27     ` Martin K. Petersen [this message]
2020-07-22 14:34       ` Bart Van Assche
2020-07-27  9:33     ` Pavel Machek
     [not found]   ` <CGME20200713103423epcms2p8442ee7cc22395e4a4cedf224f95c45e8@epcms2p3>
2020-07-13 10:38     ` [PATCH v6 1/5] scsi: ufs: Add UFS feature related parameter Daejun Park
2020-07-13 12:13       ` Can Guo
2020-07-13 10:58     ` [PATCH v6 5/5] scsi: ufs: Prepare HPB read for cached sub-region Daejun Park
2020-07-27  6:18     ` [PATCH v6 2/5] scsi: ufs: Add UFS-feature layer Daejun Park
2020-08-04 18:43       ` Bart Van Assche
     [not found]   ` <CGME20200713103423epcms2p8442ee7cc22395e4a4cedf224f95c45e8@epcms2p1>
2020-07-13 10:50     ` [PATCH v6 3/5] scsi: ufs: Introduce HPB module Daejun Park
2020-08-04 23:33     ` Re: [PATCH v6 2/5] scsi: ufs: Add UFS-feature layer Daejun Park

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