RE: [RFC PATCH v3 0/5] scsi: ufs: Add Host Performance Booster Support

["Alim Akhtar" <alim.akhtar@samsung.com>]

> -----Original Message-----
> From: Avri Altman <Avri.Altman@wdc.com>
> Sent: 30 June 2020 12:09
> To: daejun7.park@samsung.com; Bean Huo <huobean@gmail.com>;
> jejb@linux.ibm.com; martin.petersen@oracle.com; asutoshd@codeaurora.org;
> stanley.chu@mediatek.com; cang@codeaurora.org; bvanassche@acm.org;
> tomas.winkler@intel.com; ALIM AKHTAR <alim.akhtar@samsung.com>
> Cc: linux-scsi@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: [RFC PATCH v3 0/5] scsi: ufs: Add Host Performance Booster
> Support
> 
> Hi,
> 
> >
> > Hi Bean,
> > > On Mon, 2020-06-29 at 15:15 +0900, Daejun Park wrote:
> > > > > Seems you intentionally ignored to give you comments on my
> > > > > suggestion.
> > > > > let me provide the reason.
> > > >
> > > > Sorry! I replied to your comment (
> > > > https://protect2.fireeye.com/url?k=be575021-e3854728-be56db6e-
> > 0cc47a31cdf8-
> >
> 6c7d0e1e42762b92&q=1&u=https%3A%2F%2Flkml.org%2Flkml%2F2020%2F6%
> > 2F15%2F1492),
> > > > but you didn't reply on that. I thought you agreed because you
> > > > didn't send any more comments.
> > > >
> > > >
> > > > > Before submitting your next version patch, please check your L2P
> > > > > mapping HPB reqeust submission logical algorithem. I have did
> > > >
> > > > We are also reviewing the code that you submitted before.
> > > > It seems to be a performance improvement as it sends a map request
> > > > directly.
> > > >
> > > > > performance comparison testing on 4KB, there are about 13%
> > > > > performance drop. Also the hit count is lower. I don't know if
> > > > > this is related to
> > > >
> > > > It is interesting that there is actually a performance improvement.
> > > > Could you share the test environment, please? However, I think
> > > > stability is important to HPB driver. We have tested our method
> > > > with the real products and the HPB 1.0 driver is based on that.
> > >
> > > I just run fio benchmark tool with --rw=randread, --bs=4kb, --
> > > size=8G/10G/64G/100G. and see what performance diff with the direct
> > > submission approach.
> >
> > Thanks!
> >
> > > > After this patch, your approach can be done as an incremental patch?
> > > > I would
> > > > like to test the patch that you submitted and verify it.
> > > >
> > > > > your current work queue scheduling, since you didn't add the
> > > > > timer for each HPB request.
> > > >
> > >
> > > Taking into consideration of the HPB 2.0, can we submit the HPB
> > > write request to the SCSI layer? if not, it will be a direct submission way.
> > > why not directly use direct way? or maybe you have a more advisable
> > > approach to work around this. would you please share with us.
> > > appreciate.
> >
> > I am considering a direct submission way for the next version.
> > We will implement the write buffer command of HPB 2.0, after patching
> > HPB 1.0.
> >
> > As for the direct submission of HPB releated command including HPB
> > write buffer, I think we'd better discuss the right approach in depth
> > before moving on to the next step.
> I vote to stay with the current implementation because:
> 1) Bean is probably right about 2.0, but it's out of scope for now -
>     there is a long way to go before we'll need to worry about it
> 2) For now, we should focus on the functional flows.
>     Performance issues, should such issues indeed exists, can be dealt with  later.
> And,
> 3) The current code base is running in production for more than 3 years now.
>      I am not so eager to dump a robust, well debugged code unless it absolutely
> necessary.
> 
Avri and Bean,
I think this is good approach to take, and let us add incremental patches to add future specification enhancements.
 
> Thanks,
> Avri
>