From: Keith Busch <keith.busch@intel.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jens Axboe <axboe@fb.com>,
Stefan Haberland <sth@linux.vnet.ibm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-s390 <linux-s390@vger.kernel.org>,
Sebastian Ott <sebott@linux.vnet.ibm.com>
Subject: Re: [BUG] Regression introduced with "block: split bios to max possible length"
Date: Fri, 22 Jan 2016 14:56:00 +0000 [thread overview]
Message-ID: <20160122145559.GA21984@localhost.localdomain> (raw)
In-Reply-To: <CA+55aFwGRQb_2SUTj8A9MzTC4WCVC37p64t5obUfTvLNyctjKA@mail.gmail.com>
On Thu, Jan 21, 2016 at 08:15:37PM -0800, Linus Torvalds wrote:
> For the case of nvme, for example, I think the max sector number is so
> high that you'll never hit that anyway, and you'll only ever hit the
> chunk limit. No?
The device's max transfer and chunk size are not very large, both fixed
at 128KB. We can lose ~70% of potential throughput when IO isn't aligned,
and end users reported this when the block layer stopped splitting on
alignment for the NVMe drive.
So it's a big deal for this h/w, but now I feel awkward defending a
device specific feature for the generic block layer.
Anyway, the patch was developed with incorrect assumptions. I'd still
like to try again after reconciling the queue limit constraints, but
I defer to Jens for the near term.
Thanks!
next prev parent reply other threads:[~2016-01-22 14:56 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-21 14:57 [BUG] Regression introduced with "block: split bios to max possible length" Stefan Haberland
2016-01-21 21:34 ` Jens Axboe
2016-01-21 21:34 ` Jens Axboe
2016-01-21 22:51 ` Keith Busch
2016-01-22 1:12 ` Linus Torvalds
2016-01-22 3:21 ` Keith Busch
2016-01-22 4:15 ` Linus Torvalds
2016-01-22 14:56 ` Keith Busch [this message]
2016-01-22 17:15 ` Jens Axboe
2016-01-22 15:06 ` Ming Lei
2016-01-22 17:03 ` Linus Torvalds
2016-01-22 17:48 ` Ming Lei
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