From: NeilBrown <neilb@suse.de>
To: Alasdair G Kergon <agk@redhat.com>
Cc: Ming Lin <mlin@kernel.org>, Mike Snitzer <snitzer@redhat.com>,
lkml <linux-kernel@vger.kernel.org>,
Christoph Hellwig <hch@lst.de>,
Kent Overstreet <kent.overstreet@gmail.com>,
Jens Axboe <axboe@kernel.dk>, Dongsu Park <dpark@posteo.net>,
Christoph Hellwig <hch@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Ming Lei <ming.lei@canonical.com>,
dm-devel@redhat.com, Lars Ellenberg <drbd-dev@lists.linbit.com>,
drbd-user@lists.linbit.com, Jiri Kosina <jkosina@suse.cz>,
Geoff Levand <geoff@infradead.org>, Jim Paris <jim@jtan.com>,
Joshua Morris <josh.h.morris@us.ibm.com>,
Philip Kelleher <pjk1939@linux.vnet.ibm.com>,
Minchan Kim <minchan@kernel.org>, Nitin Gupta <ngupta@vflare.org>,
Oleg Drokin <oleg.drokin@intel.com>,
Andreas Dilger <andreas.dilger@intel.com>,
Dave Chinner <dchinner@redhat.com>
Subject: Re: [PATCH v4 01/11] block: make generic_make_request handle arbitrarily sized bios
Date: Wed, 27 May 2015 09:06:40 +1000 [thread overview]
Message-ID: <20150527090640.44c346e2@notabene.brown> (raw)
In-Reply-To: <20150526153414.GA31182@agk-dp.fab.redhat.com>
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On Tue, 26 May 2015 16:34:14 +0100 Alasdair G Kergon <agk@redhat.com> wrote:
> On Tue, May 26, 2015 at 08:02:08AM -0700, Ming Lin wrote:
> > Now bio_add_page() can build lager bios.
> > And blk_queue_split() can split the bios in ->make_request() if needed.
>
> But why not try to make the bio the right size in the first place so you
> don't have to incur the performance impact of splitting?
Because we don't know what the "right" size is. And the "right" size can
change when array reconfiguration happens.
Splitting has to happen somewhere, if only in bio_addpage where it decides to
create a new bio rather than add another page to the current one. So moving
the split to a different level of the stack shouldn't necessarily change the
performance profile.
Obviously testing is important to confirm that.
NeilBrown
>
> What performance testing have you yet done to demonstrate the *actual* impact
> of this patchset in situations where merge_bvec_fn is currently a net benefit?
>
> Alasdair
>
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next prev parent reply other threads:[~2015-05-26 23:08 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-22 18:18 [PATCH v4 00/11] simplify block layer based on immutable biovecs Ming Lin
2015-05-22 18:18 ` [PATCH v4 01/11] block: make generic_make_request handle arbitrarily sized bios Ming Lin
2015-05-25 5:46 ` NeilBrown
2015-05-26 14:36 ` Mike Snitzer
2015-05-26 15:02 ` Ming Lin
2015-05-26 15:34 ` Alasdair G Kergon
2015-05-26 23:06 ` NeilBrown [this message]
2015-05-27 0:40 ` [dm-devel] " Alasdair G Kergon
2015-05-27 8:20 ` Christoph Hellwig
2015-05-26 16:04 ` Mike Snitzer
2015-05-26 17:17 ` Ming Lin
2015-05-27 23:42 ` Ming Lin
2015-05-28 0:36 ` Alasdair G Kergon
2015-05-28 5:54 ` Ming Lin
2015-05-29 7:05 ` Ming Lin
2015-05-29 15:15 ` Mike Snitzer
2015-06-01 6:02 ` Ming Lin
2015-06-02 20:59 ` Ming Lin
2015-06-04 21:06 ` Mike Snitzer
2015-06-04 22:21 ` Ming Lin
2015-06-05 0:06 ` Mike Snitzer
2015-06-05 5:21 ` Ming Lin
2015-06-09 6:09 ` Ming Lin
2015-06-10 21:20 ` Ming Lin
2015-06-10 21:46 ` Mike Snitzer
2015-06-10 22:06 ` Ming Lin
2015-06-12 5:49 ` Ming Lin
2015-06-18 5:27 ` Ming Lin
2015-05-22 18:18 ` [PATCH v4 02/11] block: simplify bio_add_page() Ming Lin
2015-05-22 18:18 ` [PATCH v4 03/11] bcache: remove driver private bio splitting code Ming Lin
2015-05-22 18:18 ` [PATCH v4 04/11] btrfs: remove bio splitting and merge_bvec_fn() calls Ming Lin
2015-05-22 18:18 ` [PATCH v4 05/11] block: remove split code in blkdev_issue_discard Ming Lin
2015-05-22 18:18 ` [PATCH v4 06/11] md/raid5: get rid of bio_fits_rdev() Ming Lin
2015-05-25 5:48 ` NeilBrown
2015-05-25 7:03 ` Ming Lin
2015-05-25 7:54 ` NeilBrown
2015-05-25 14:17 ` Christoph Hellwig
2015-05-26 14:33 ` Ming Lin
2015-05-26 22:32 ` Ming Lin
2015-05-26 23:03 ` NeilBrown
2015-05-26 23:42 ` Ming Lin
2015-05-27 0:38 ` NeilBrown
2015-05-27 8:15 ` Christoph Hellwig
2015-05-22 18:18 ` [PATCH v4 07/11] md/raid5: split bio for chunk_aligned_read Ming Lin
2015-05-22 18:18 ` [PATCH v4 08/11] block: kill merge_bvec_fn() completely Ming Lin
2015-05-25 5:49 ` NeilBrown
2015-05-25 14:04 ` Christoph Hellwig
2015-05-25 15:02 ` Ilya Dryomov
2015-05-25 15:08 ` Christoph Hellwig
2015-05-25 15:19 ` Ilya Dryomov
2015-05-25 15:35 ` Alex Elder
2015-05-22 18:18 ` [PATCH v4 09/11] fs: use helper bio_add_page() instead of open coding on bi_io_vec Ming Lin
2015-05-22 18:18 ` [PATCH v4 10/11] block: remove bio_get_nr_vecs() Ming Lin
2015-05-22 18:18 ` [PATCH v4 11/11] Documentation: update notes in biovecs about arbitrarily sized bios Ming Lin
2015-05-23 14:15 ` [PATCH v4 00/11] simplify block layer based on immutable biovecs Christoph Hellwig
2015-05-24 7:37 ` Ming Lin
2015-05-25 13:51 ` Christoph Hellwig
2015-05-29 6:39 ` Ming Lin
2015-06-01 6:15 ` Ming Lin
2015-06-03 6:57 ` Christoph Hellwig
2015-06-03 13:28 ` Jeff Moyer
2015-06-03 17:06 ` Ming Lin
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