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From: Jan Kara <jack@suse.cz>
To: Keith Busch <keith.busch@intel.com>
Cc: Jan Kara <jack@suse.cz>, Kanchan Joshi <joshi.k@samsung.com>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"jack@suse.com" <jack@suse.com>,
	"david@fromorbit.com" <david@fromorbit.com>,
	"tytso@mit.edu" <tytso@mit.edu>,
	"prakash.v@samsung.com" <prakash.v@samsung.com>,
	Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH v2 0/4] Write-hint for FS journal
Date: Tue, 29 Jan 2019 11:07:02 +0100
Message-ID: <20190129100702.GA29981@quack2.suse.cz> (raw)
In-Reply-To: <20190128232423.GD15302@localhost.localdomain>

On Mon 28-01-19 16:24:24, Keith Busch wrote:
> On Mon, Jan 28, 2019 at 04:47:09AM -0800, Jan Kara wrote:
> > On Fri 25-01-19 09:23:53, Keith Busch wrote:
> > > On Wed, Jan 09, 2019 at 09:00:57PM +0530, Kanchan Joshi wrote:
> > > > Towards supporing write-hints/streams for filesystem journal.                   
> > > >                                                                                 
> > > > Here is the v1 patch for background -                                           
> > > > https://marc.info/?l=linux-fsdevel&m=154444637519020&w=2                        
> > > >                                                                                 
> > > > Changes since v1:                                                               
> > > > - introduce four more hints for in-kernel use, as recommended by Dave chinner   
> > > >   & Jens axboe. This isolates kernel-mode hints from user-mode ones.            
> > > 
> > > The nvme driver disables streams if the controller doesn't support
> > > BLK_MAX_WRITE_HINT number of streams, so this series breaks the feature
> > > for controllers that only support up to 4.
> > 
> > Right. Do you know if there are such controllers? Or are you just afraid
> > that there could be?
> 
> I've asked around, and the concensus I received is all currently support
> at least 8, but they couldn't say if that would be true for potential
> lower budget products. Can we implement a reasonable fallback to use
> what's available?

OK, thanks for input. So probably we should just map kernel stream IDs to 0
if the device doesn't support them. But that probably means we need to
propagate number of available streams up from NVME into the block layer so
that this can be handled reasonably seamlessly. Jens, Kanchan?

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20190109153328epcas2p4643cbdc7a2182b47893a2bcaa0778e17@epcas2p4.samsung.com>
2019-01-09 15:30 ` Kanchan Joshi
     [not found]   ` <CGME20190109153332epcas1p187b419176a8d1d0be4982a275c0b9e86@epcas1p1.samsung.com>
2019-01-09 15:30     ` [PATCH 1/4] block: Increase count of supported write-hints Kanchan Joshi
     [not found]   ` <CGME20190109153336epcas2p29b3275b6c545e483a3f43b92268f08bf@epcas2p2.samsung.com>
2019-01-09 15:30     ` [PATCH 2/4] fs: introduce four macros for in-kernel hints Kanchan Joshi
2019-01-23 18:27       ` [PATCH 2/4] " Javier González
2019-01-24  8:35         ` Jan Kara
2019-01-24  9:23           ` Javier González
     [not found]   ` <CGME20190109153339epcas2p4691a898dde0174a7565d62fcb3be0b6d@epcas2p4.samsung.com>
2019-01-09 15:31     ` [PATCH 3/4] fs: introduce APIs to enable sending write-hint with buffer-head Kanchan Joshi
     [not found]   ` <CGME20190109153342epcas2p3208f62a4dd876f8e1765b48f8aec2432@epcas2p3.samsung.com>
2019-01-09 15:31     ` [PATCH 4/4] fs/ext4,jbd2: add support for passing write-hint with journal Kanchan Joshi
2019-01-24  8:50       ` Jan Kara
2019-01-23 18:35   ` [PATCH v2 0/4] Write-hint for FS journal Javier González
2019-01-24  8:29   ` Jan Kara
2019-01-25 14:20     ` Kanchan Joshi
2019-01-25 16:23   ` Keith Busch
2019-01-28 12:47     ` Jan Kara
2019-01-28 23:24       ` Keith Busch
2019-01-29 10:07         ` Jan Kara [this message]
2019-01-30  0:13           ` Dave Chinner
2019-01-30 13:54             ` Kanchan Joshi
2019-02-05 11:50               ` Jan Kara
2019-02-05 22:53                 ` Dave Chinner

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