From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: "Elliott, Robert (Persistent Memory)" <elliott@hpe.com>,
Jens Axboe <axboe@kernel.dk>,
Mikael Pettersson <mikpelinux@gmail.com>
Cc: Linux SPARC Kernel Mailing List <sparclinux@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-scsi <linux-scsi@vger.kernel.org>
Subject: Re: [5.0-rc5 regression] "scsi: kill off the legacy IO path" causes 5 minute delay during boot on Sun Blade 2500
Date: Mon, 11 Feb 2019 20:15:57 -0800 [thread overview]
Message-ID: <1549944957.2857.13.camel@HansenPartnership.com> (raw)
In-Reply-To: <AT5PR8401MB1169D3DBEBC4F88D76BD1710AB650@AT5PR8401MB1169.NAMPRD84.PROD.OUTLOOK.COM>
On Tue, 2019-02-12 at 03:37 +0000, Elliott, Robert (Persistent Memory)
wrote:
> > -----Original Message-----
> > From: linux-kernel-owner@vger.kernel.org <linux-kernel-
> > owner@vger.kernel.org> On Behalf Of Jens Axboe
> > Sent: Monday, February 11, 2019 8:50 PM
> > To: James Bottomley <James.Bottomley@HansenPartnership.com>; Mikael
> > Pettersson <mikpelinux@gmail.com>
> > Cc: Linux SPARC Kernel Mailing List <sparclinux@vger.kernel.org>;
> > linux-block@vger.kernel.org; linux-kernel@vger.kernel.org; linux-
> > scsi
> > <linux-scsi@vger.kernel.org>
> > Subject: Re: [5.0-rc5 regression] "scsi: kill off the legacy IO
> > path"
> > causes 5 minute delay during boot on Sun Blade 2500
>
> ...
>
> > > We can either fix this by setting the QUEUE_FLAG_ADD_RANDOM if
> > > there's no 0xB1 page or by setting the default as Jens proposed.
> >
> > I'd recommend just doing my patch, since that'll be the same
> > behavior that SCSI had before.
>
> When blk-mq and scsi-mq were introduced to boost SAS SSDs over
> 1 million IOPS, this was purposely kept off, because it generated
> a noticeable 3-12 us latency blip whenever the "fast_mix" code ran
> out of bits. If Jens' patch changes the default to be enabled for
> all scsi-mq users, that'll be a change for the newer legacy
> scsi-mq users (except for users that don't trust the default and
> always set the value in sysfs).
All high IOPs devices have a device characteristics page, so even if we
default this to ON, it will get turned off for these devices which
should be the desired result regardless of the default setting.
James
next prev parent reply other threads:[~2019-02-12 4:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-09 17:04 [5.0-rc5 regression] "scsi: kill off the legacy IO path" causes 5 minute delay during boot on Sun Blade 2500 Mikael Pettersson
2019-02-09 18:19 ` James Bottomley
2019-02-10 9:17 ` Mikael Pettersson
2019-02-10 15:44 ` James Bottomley
2019-02-10 16:05 ` Jens Axboe
2019-02-10 16:25 ` James Bottomley
2019-02-10 16:35 ` Jens Axboe
2019-02-11 15:25 ` James Bottomley
2019-02-11 15:28 ` Jens Axboe
2019-02-11 15:42 ` James Bottomley
2019-02-11 15:46 ` Jens Axboe
2019-02-11 16:28 ` James Bottomley
2019-02-11 16:31 ` Jens Axboe
2019-02-12 2:13 ` James Bottomley
2019-02-12 2:50 ` Jens Axboe
2019-02-12 3:37 ` Elliott, Robert (Persistent Memory)
2019-02-12 4:15 ` James Bottomley [this message]
2019-02-12 15:24 ` James Bottomley
2019-02-12 15:27 ` Jens Axboe
2019-02-14 18:35 ` Mikael Pettersson
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