From: Kanchan Joshi <joshiiitr@gmail.com>
To: Viacheslav Dubeyko <slava@dubeyko.com>
Cc: "Kanchan Joshi" <joshi.k@samsung.com>,
"Jens Axboe" <axboe@kernel.dk>, "Keith Busch" <kbusch@kernel.org>,
"Christoph Hellwig" <hch@lst.de>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
"Javier González" <javier.gonz@samsung.com>,
"Bart Van Assche" <bvanassche@acm.org>,
david@fromorbit.com, gost.dev@samsung.com,
"Hui Qi" <hui81.qi@samsung.com>,
"Nitesh Shetty" <nj.shetty@samsung.com>
Subject: Re: [PATCH] nvme: enable FDP support
Date: Tue, 14 May 2024 21:30:03 -0600 [thread overview]
Message-ID: <CA+1E3rJtJpxk3EmTmtJWDFwP8km0xqRPt2QeQTRar7sTHtdD2Q@mail.gmail.com> (raw)
In-Reply-To: <88421397-1B95-4B2A-A302-55A919BCE98E@dubeyko.com>
On Tue, May 14, 2024 at 1:00 PM Viacheslav Dubeyko <slava@dubeyko.com> wrote:
> > On May 14, 2024, at 9:47 PM, Kanchan Joshi <joshiiitr@gmail.com> wrote:
> >
> > On Mon, May 13, 2024 at 2:04 AM Viacheslav Dubeyko <slava@dubeyko.com> wrote:
> >>
> >>
> >>
> >>> On May 10, 2024, at 4:40 PM, Kanchan Joshi <joshi.k@samsung.com> wrote:
> >>>
> >>> Flexible Data Placement (FDP), as ratified in TP 4146a, allows the host
> >>> to control the placement of logical blocks so as to reduce the SSD WAF.
> >>>
> >>> Userspace can send the data lifetime information using the write hints.
> >>> The SCSI driver (sd) can already pass this information to the SCSI
> >>> devices. This patch does the same for NVMe.
> >>>
> >>> Fetches the placement-identifiers (plids) if the device supports FDP.
> >>> And map the incoming write-hints to plids.
> >>>
> >>
> >>
> >> Great! Thanks for sharing the patch.
> >>
> >> Do we have documentation that explains how, for example, kernel-space
> >> file system can work with block layer to employ FDP?
> >
> > This is primarily for user driven/exposed hints. For file system
> > driven hints, the scheme is really file system specific and therefore,
> > will vary from one to another.
> > F2FS is one (and only at the moment) example. Its 'fs-based' policy
> > can act as a reference for one way to go about it.
>
> Yes, I completely see the point. I would like to employ the FDP in my
> kernel-space file system (SSDFS). And I have a vision how I can do it.
> But I simply would like to see some documentation with the explanation of
> API and limitations of FDP for the case of kernel-space file systems.
Nothing complicated for early experimentation.
Once FS has determined the hint value, it can put that into
bio->bi_write_hint and send bio down.
If SSDFS cares about user-exposed hints too, it can choose different
hint values than what is exposed to user-space.
Or it can do what F2FS does - use the mount option as a toggle to
reuse the same values either for user-hints or fs-defined hints.
next prev parent reply other threads:[~2024-05-14 21:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20240510134740epcas5p24ef1c2d6e8934c1c79b01c849e7ccb41@epcas5p2.samsung.com>
2024-05-10 13:40 ` [PATCH] nvme: enable FDP support Kanchan Joshi
2024-05-10 19:30 ` Keith Busch
2024-05-11 9:20 ` kernel test robot
2024-05-13 7:56 ` Viacheslav Dubeyko
2024-05-14 8:44 ` Joel Granados
2024-05-14 18:47 ` Kanchan Joshi
2024-05-14 19:00 ` Viacheslav Dubeyko
2024-05-15 3:30 ` Kanchan Joshi [this message]
2024-05-14 21:40 ` Viacheslav Dubeyko
2024-05-17 16:27 ` Kanchan Joshi
2024-05-17 17:22 ` Viacheslav Dubeyko
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