From: Jens Axboe <axboe@kernel.dk>
To: "Matias Bjørling" <m@bjorling.me>, "Jens Axboe" <axboe@fb.com>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Cc: ming.l@ssi.samsung.com
Subject: Re: [PATCH 1/6] block: add support for carrying a stream ID in a bio
Date: Tue, 24 Mar 2015 11:26:54 -0600 [thread overview]
Message-ID: <55119E5E.6020405@kernel.dk> (raw)
In-Reply-To: <55119AAE.9030202@bjorling.me>
On 03/24/2015 11:11 AM, Matias Bjørling wrote:
> On 03/24/2015 04:26 PM, Jens Axboe wrote:
>> The top bits of bio->bi_flags are reserved for keeping the
>> allocation pool, set aside the next four bits for carrying
>> a stream ID. That leaves us with support for 15 streams,
>> 0 is reserved as a "stream not set" value.
>
> 15 streams seem very limited. Can this be extended? e.g. 16 bits.
>
> 15 streams is enough for 1-4 applications. More, and applications starts
> to fight over the same stream id's, leading them to place different age
> data in same flash blocks and push us back to square one.
>
> I understand that Samsung multi-stream SSD supports a limited amount of
> streams, more advance implementations should provide higher limits.
Pushing it higher is not a big deal as far as the implementation goes,
though 16 bits might be stealing a bit too much space for this. On
32-bit archs, we have 18 bits currently free that we can abuse. The
Samsung device supports 16 streams. That's honestly a lot more than I
would expect most devices to support in hardware, 16 is a lot of open
erase blocks and write append points. Obviously the open channel effort
would make that more feasible, though.
--
Jens Axboe
next prev parent reply other threads:[~2015-03-24 17:27 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-24 15:26 [PATCH RFC] Support for write stream IDs Jens Axboe
2015-03-24 15:26 ` [PATCH 1/6] block: add support for carrying a stream ID in a bio Jens Axboe
2015-03-24 17:11 ` Matias Bjørling
2015-03-24 17:26 ` Jens Axboe [this message]
2015-03-24 22:07 ` Ming Lin-SSI
2015-03-25 1:42 ` Jens Axboe
2015-03-25 8:11 ` Matias Bjørling
2015-03-25 18:36 ` Ming Lin-SSI
2015-03-25 2:30 ` Dave Chinner
2015-04-12 10:42 ` Dmitry Monakhov
2015-03-24 15:26 ` [PATCH 2/6] Add support for per-file stream ID Jens Axboe
2015-03-24 15:27 ` [PATCH 3/6] direct-io: add support for write stream IDs Jens Axboe
2015-03-25 2:43 ` Dave Chinner
2015-03-25 14:26 ` Jens Axboe
2015-04-10 23:50 ` Ming Lin
2015-04-11 0:06 ` Ming Lin
2015-04-11 11:59 ` Dave Chinner
2015-04-17 6:20 ` Ming Lin
2015-04-17 23:06 ` Dave Chinner
2015-04-17 23:11 ` Jens Axboe
2015-04-17 23:51 ` Dave Chinner
2015-04-18 2:00 ` Jens Axboe
2015-04-17 15:17 ` Jens Axboe
2015-03-24 15:27 ` [PATCH 4/6] Add stream ID support for buffered writeback Jens Axboe
2015-03-25 2:40 ` Dave Chinner
2015-03-25 14:17 ` Jens Axboe
2015-03-24 15:27 ` [PATCH 5/6] btrfs: add support for buffered writeback stream ID Jens Axboe
2015-03-24 15:27 ` [PATCH 6/6] xfs: " Jens Axboe
2015-03-25 2:41 ` Dave Chinner
2015-03-24 17:03 ` [PATCH RFC] Support for write stream IDs Jeff Moyer
2015-03-24 17:08 ` Jens Axboe
2015-03-24 21:46 ` Ming Lin-SSI
2015-03-24 21:48 ` Jens Axboe
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