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From: Keith Busch <>
To: Eduard Hasenleithner <>
Cc: Sagi Grimberg <>,
Subject: Re: [RFC PATCH] Workaround for discard on non-conformant nvme devices
Date: Thu, 7 Nov 2019 06:34:03 +0900	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Wed, Nov 06, 2019 at 10:10:58PM +0100, Eduard Hasenleithner wrote:
> On 06.11.19 21:43, Keith Busch wrote:
> > On Wed, Nov 06, 2019 at 09:22:00PM +0100, Eduard Hasenleithner wrote:
> > > Couldn't we just simply use the discard_page for all discards?
> > 
> > That's normally just a fallback to ensure forward progress under memory
> > pressure. It's not particularly performant, though.
> So we are accepting a considerable performance impact for the "broken"
> devices?

I'd wager the devices that got this wrong are operating on DSMs beyond
QD1 anyway, the impact to them is probably much less than "considerable".
> > > Are there even nvme devices out there which have conformant behavior in this
> > > respect?
> > 
> > I believe most of them do conform, but I don't have a large sample size
> > to confirm.
> Do you have an IO-MMU active on your setup?

Sometimes, but that's not why I know at least some devices are
compliant. I've wasted too many hours analyzing protocol traces.

Linux-nvme mailing list

      reply	other threads:[~2019-11-06 21:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-04 21:47 [RFC PATCH] Workaround for discard on non-conformant nvme devices Eduard Hasenleithner
2019-11-06 16:52 ` Sagi Grimberg
2019-11-06 18:23   ` Keith Busch
2019-11-06 20:22     ` Eduard Hasenleithner
2019-11-06 20:43       ` Keith Busch
2019-11-06 21:10         ` Eduard Hasenleithner
2019-11-06 21:34           ` Keith Busch [this message]

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