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From: "Kani, Toshimitsu" <toshi.kani@hpe.com>
To: "dan.j.williams@intel.com" <dan.j.williams@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
Subject: Re: [PATCH] libnvdimm: rework region badblocks clearing
Date: Mon, 1 May 2017 16:20:09 +0000	[thread overview]
Message-ID: <1493655607.30303.19.camel@hpe.com> (raw)
In-Reply-To: <CAPcyv4hwt8nf5+ADQyj_ahtACZq+if__SqC3dBZTCd==4OWZXA@mail.gmail.com>

On Mon, 2017-05-01 at 09:16 -0700, Dan Williams wrote:
> On Mon, May 1, 2017 at 9:12 AM, Kani, Toshimitsu <toshi.kani@hpe.com>
> wrote:
> > On Mon, 2017-05-01 at 08:52 -0700, Dan Williams wrote:
> > > On Mon, May 1, 2017 at 8:43 AM, Dan Williams <dan.j.williams@inte
> > > l.co
> > > m> wrote:
> > > > On Mon, May 1, 2017 at 8:34 AM, Kani, Toshimitsu <toshi.kani@hp
> > > > e.co
> > > > m> wrote:
> > > > > On Sun, 2017-04-30 at 05:39 -0700, Dan Williams wrote:
> > 
> >  :
> > > > > 
> > > > > Hi Dan,
> > > > > 
> > > > > I was testing the change with CONFIG_DEBUG_ATOMIC_SLEEP set
> > > > > this time, and hit the following BUG with BTT.  This is a
> > > > > separate issue (not introduced by this patch), but it shows
> > > > > that we have an issue with the DSM call path as well.
> > > > 
> > > > Ah, great find, thanks! We don't see this in the unit tests
> > > > because the nfit_test infrastructure takes no sleeping actions
> > > > in its simulated DSM path. Outside of converting btt to use
> > > > sleeping locks I'm not sure I see a path forward. I wonder how
> > > > bad the performance impact of that would be? Perhaps with
> > > > opportunistic spinning it won't be so bad, but I don't see
> > > > another choice.
> > > 
> > > It's worse than that. Part of the performance optimization of BTT
> > > I/O was to avoid locking altogether when we could rely on a BTT
> > > lane percpu, so that would also need to be removed.
> > 
> > I do not have a good idea either, but I'd rather disable this
> > clearing in the regular BTT write path than adding sleeping locks
> > to BTT. Clearing a bad block in the BTT write path is
> > difficult/challenging since it allocates a new block.
> 
> Actually, that may make things easier. Can we teach BTT to track
> error blocks and clear them before they are reassigned?

I was thinking the same after sending it.  I think we should be able to
do that.

Thanks,
-Toshi
_______________________________________________
Linux-nvdimm mailing list
Linux-nvdimm@lists.01.org
https://lists.01.org/mailman/listinfo/linux-nvdimm

WARNING: multiple messages have this Message-ID (diff)
From: "Kani, Toshimitsu" <toshi.kani@hpe.com>
To: "dan.j.williams@intel.com" <dan.j.williams@intel.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
	"dave.jiang@intel.com" <dave.jiang@intel.com>,
	"vishal.l.verma@intel.com" <vishal.l.verma@intel.com>
Subject: Re: [PATCH] libnvdimm: rework region badblocks clearing
Date: Mon, 1 May 2017 16:20:09 +0000	[thread overview]
Message-ID: <1493655607.30303.19.camel@hpe.com> (raw)
In-Reply-To: <CAPcyv4hwt8nf5+ADQyj_ahtACZq+if__SqC3dBZTCd==4OWZXA@mail.gmail.com>

On Mon, 2017-05-01 at 09:16 -0700, Dan Williams wrote:
> On Mon, May 1, 2017 at 9:12 AM, Kani, Toshimitsu <toshi.kani@hpe.com>
> wrote:
> > On Mon, 2017-05-01 at 08:52 -0700, Dan Williams wrote:
> > > On Mon, May 1, 2017 at 8:43 AM, Dan Williams <dan.j.williams@inte
> > > l.co
> > > m> wrote:
> > > > On Mon, May 1, 2017 at 8:34 AM, Kani, Toshimitsu <toshi.kani@hp
> > > > e.co
> > > > m> wrote:
> > > > > On Sun, 2017-04-30 at 05:39 -0700, Dan Williams wrote:
> > 
> >  :
> > > > > 
> > > > > Hi Dan,
> > > > > 
> > > > > I was testing the change with CONFIG_DEBUG_ATOMIC_SLEEP set
> > > > > this time, and hit the following BUG with BTT.  This is a
> > > > > separate issue (not introduced by this patch), but it shows
> > > > > that we have an issue with the DSM call path as well.
> > > > 
> > > > Ah, great find, thanks! We don't see this in the unit tests
> > > > because the nfit_test infrastructure takes no sleeping actions
> > > > in its simulated DSM path. Outside of converting btt to use
> > > > sleeping locks I'm not sure I see a path forward. I wonder how
> > > > bad the performance impact of that would be? Perhaps with
> > > > opportunistic spinning it won't be so bad, but I don't see
> > > > another choice.
> > > 
> > > It's worse than that. Part of the performance optimization of BTT
> > > I/O was to avoid locking altogether when we could rely on a BTT
> > > lane percpu, so that would also need to be removed.
> > 
> > I do not have a good idea either, but I'd rather disable this
> > clearing in the regular BTT write path than adding sleeping locks
> > to BTT. Clearing a bad block in the BTT write path is
> > difficult/challenging since it allocates a new block.
> 
> Actually, that may make things easier. Can we teach BTT to track
> error blocks and clear them before they are reassigned?

I was thinking the same after sending it.  I think we should be able to
do that.

Thanks,
-Toshi

  reply	other threads:[~2017-05-01 16:20 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-30 12:39 [PATCH] libnvdimm: rework region badblocks clearing Dan Williams
2017-04-30 12:39 ` Dan Williams
2017-05-01 15:34 ` Kani, Toshimitsu
2017-05-01 15:34   ` Kani, Toshimitsu
2017-05-01 15:43   ` Dan Williams
2017-05-01 15:43     ` Dan Williams
2017-05-01 15:52     ` Dan Williams
2017-05-01 15:52       ` Dan Williams
2017-05-01 16:12       ` Kani, Toshimitsu
2017-05-01 16:12         ` Kani, Toshimitsu
2017-05-01 16:16         ` Dan Williams
2017-05-01 16:16           ` Dan Williams
2017-05-01 16:20           ` Kani, Toshimitsu [this message]
2017-05-01 16:20             ` Kani, Toshimitsu
2017-05-01 16:38             ` Dan Williams
2017-05-01 16:38               ` Dan Williams
2017-05-01 16:42               ` Verma, Vishal L
2017-05-01 16:42                 ` Verma, Vishal L
2017-05-01 16:45                 ` Kani, Toshimitsu
2017-05-01 16:45                   ` Kani, Toshimitsu
2017-05-01 21:26 ` Kani, Toshimitsu
2017-05-01 21:26   ` Kani, Toshimitsu
2017-05-01 23:09   ` Dan Williams
2017-05-01 23:09     ` Dan Williams

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