From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Kanchan Joshi <joshi.k@samsung.com>,
axboe@kernel.dk, sagi@grimberg.me,
linux-nvme@lists.infradead.org, javier.gonz@samsung.com,
bvanassche@acm.org, gost.dev@samsung.com,
Hui Qi <hui81.qi@samsung.com>,
Nitesh Shetty <nj.shetty@samsung.com>
Subject: Re: [PATCH v2] nvme: enable FDP support
Date: Tue, 11 Jun 2024 07:47:26 +0200 [thread overview]
Message-ID: <20240611054726.GA2680@lst.de> (raw)
In-Reply-To: <ZmcTHMWb-T78Crfn@kbusch-mbp.dhcp.thefacebook.com>
On Mon, Jun 10, 2024 at 08:52:12AM -0600, Keith Busch wrote:
> I agree the FDP setup is complicated, but none of that is taken on by
> the driver. It just discovers the capabilities and maps an arbitrary
> software "hint" to an arbitrary device "hint". It's up to the
> application to use those optimally; the driver just performs the
> requested mapping.
>
> Is it because the names of those hints indicate data lifetime? These are
> just arbitrary numbers used by applications to separate placement. If
> they were called HINT_A, HINT_B, HINT_C, would that make this ok?
No, the other problem is that FDP very much has an implicit contract
that the host actually aligns to it resources units, and actually
has a really complicated mangement. It's not a simple throw a
lifetime hint at the drive. Note that the implicit is indeed very
implicit - it is a really horrible spec with a lot of assumptions
but nothing actually enforcing it. If you just use it for dumb
lifetime hints changes are that you actually increase write
amplificiation.
next prev parent reply other threads:[~2024-06-11 5:47 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20240528151007epcas5p32583675f647553923e5ba4987e9bc6ed@epcas5p3.samsung.com>
2024-05-28 15:02 ` [PATCH v2] nvme: enable FDP support Kanchan Joshi
2024-06-07 15:14 ` Keith Busch
2024-06-08 5:17 ` Christoph Hellwig
2024-06-10 10:38 ` Kanchan Joshi
2024-06-10 11:27 ` Martin K. Petersen
2024-06-10 11:53 ` Javier González
2024-06-10 11:55 ` [PATCH v2] " Christoph Hellwig
2024-06-10 14:52 ` Keith Busch
2024-06-11 5:47 ` Christoph Hellwig [this message]
2024-06-11 14:32 ` Keith Busch
2024-06-11 19:43 ` Martin K. Petersen
2024-06-11 22:42 ` Keith Busch
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