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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 16:12:13 +0000	[thread overview]
Message-ID: <1493655131.30303.17.camel@hpe.com> (raw)
In-Reply-To: <CAPcyv4gxuez8BvtWwwcTXCKpzKp+oGQrRQG8+2iQ6XqRAfT_3g@mail.gmail.com>

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@intel.co
> m> wrote:
> > On Mon, May 1, 2017 at 8:34 AM, Kani, Toshimitsu <toshi.kani@hpe.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.

Thanks,
-Toshi
_______________________________________________
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Linux-nvdimm@lists.01.org
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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 16:12:13 +0000	[thread overview]
Message-ID: <1493655131.30303.17.camel@hpe.com> (raw)
In-Reply-To: <CAPcyv4gxuez8BvtWwwcTXCKpzKp+oGQrRQG8+2iQ6XqRAfT_3g@mail.gmail.com>

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@intel.co
> m> wrote:
> > On Mon, May 1, 2017 at 8:34 AM, Kani, Toshimitsu <toshi.kani@hpe.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.

Thanks,
-Toshi

  reply	other threads:[~2017-05-01 16:12 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 [this message]
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
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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