From: Shaohua Li <shli@kernel.org>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Jens Axboe <axboe@fb.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:SOFTWARE RAID (Multiple Disks) SUPPORT"
<linux-raid@vger.kernel.org>,
linux-block <linux-block@vger.kernel.org>,
Christoph Hellwig <hch@infradead.org>, NeilBrown <neilb@suse.com>
Subject: Re: [PATCH 00/17] md: cleanup on direct access to bvec table
Date: Thu, 16 Feb 2017 20:16:35 -0800 [thread overview]
Message-ID: <20170217041635.4hxnlqf7mh2wwtok@kernel.org> (raw)
In-Reply-To: <CACVXFVPRuikOn=zJ5fboGMyQs3rMxaUK4f-Lk0s-+HpPy+ov8w@mail.gmail.com>
On Fri, Feb 17, 2017 at 09:25:27AM +0800, Ming Lei wrote:
> Hi Shaohua,
>
> On Fri, Feb 17, 2017 at 6:16 AM, Shaohua Li <shli@kernel.org> wrote:
> > On Thu, Feb 16, 2017 at 07:45:30PM +0800, Ming Lei wrote:
> >> In MD's resync I/O path, there are lots of direct access to bio's
> >> bvec table. This patchset kills most of them, and the conversion
> >> is quite straightforward.
> >
> > I don't like this approach. The MD uses a hacky way to manage pages allocated,
> > this is the root of the problem. The patches add another hack way to do the
>
> Yes, I agree, and bio_iov_iter_get_pages() uses this kind of hacky way too
> actually.
>
> > management. I'd like to see explict management of the pages, for example, add
> > data structure in r1bio to manage the pages, then we can use existing API for
> > all the stuffes we need.
>
> Yeah, that is definitely clean, but we have to pay the following cost:
>
> - allocate at least N * (128 + 4) bytes per each r1_bio/r10_bio
> - N is pool_info.raid_disks for raid1, and conf->copies for raid10
>
> If we are happy to introduce the cost, I can take this way in V1.
It's not a big deal. The inflight bio shouldn't be big, so the r1_bio count
isn't big. We don't waste much.
Thanks,
Shaohua
prev parent reply other threads:[~2017-02-17 4:16 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-16 11:45 [PATCH 00/17] md: cleanup on direct access to bvec table Ming Lei
2017-02-16 11:45 ` [PATCH 01/17] block: introduce bio_segments_all() Ming Lei
2017-02-16 11:45 ` [PATCH 02/17] block: introduce bio_remove_last_page() Ming Lei
2017-02-16 12:08 ` Johannes Thumshirn
2017-02-16 13:30 ` Ming Lei
2017-02-16 13:40 ` Johannes Thumshirn
2017-02-16 13:59 ` Ming Lei
2017-02-16 14:10 ` Johannes Thumshirn
2017-02-16 11:45 ` [PATCH 03/17] md: raid1/raid10: use bio_remove_last_page() Ming Lei
2017-02-16 11:45 ` [PATCH 04/17] md: introduce helpers for dealing with fetch/store preallocated pages in bio Ming Lei
2017-02-16 11:45 ` [PATCH 05/17] md: raid1/raid10: use the introduced helpers Ming Lei
2017-02-16 11:45 ` [PATCH 06/17] md: raid1/raid10: borrow .bi_error as pre-allocated page index Ming Lei
2017-02-16 11:45 ` [PATCH 07/17] md: raid1/raid10: don't use .bi_vcnt to check if all pages are added Ming Lei
2017-02-16 11:45 ` [PATCH 08/17] md: raid1: simplify r1buf_pool_free() Ming Lei
2017-02-16 11:45 ` [PATCH 09/17] md: raid1/raid10: use bio helper in *_pool_free Ming Lei
2017-02-16 11:45 ` [PATCH 10/17] md: raid1: remove direct access to bvec table in fix_sync_read_error Ming Lei
2017-02-16 11:45 ` [PATCH 11/17] md: raid1: use bio helper in process_checks() Ming Lei
2017-02-16 11:45 ` [PATCH 12/17] md: raid1: avoid direct access to bvec table " Ming Lei
2017-02-17 8:33 ` kbuild test robot
2017-02-16 11:45 ` [PATCH 13/17] md: raid1: use bio_segments_all() Ming Lei
2017-02-16 12:35 ` Johannes Thumshirn
2017-02-16 13:32 ` Ming Lei
2017-02-16 13:34 ` Johannes Thumshirn
2017-02-16 13:38 ` Ming Lei
2017-02-16 11:45 ` [PATCH 14/17] md: raid10: avoid direct access to bvec table in sync_request_write() Ming Lei
2017-02-16 11:45 ` [PATCH 15/17] md: raid10: avoid direct access to bvec table in fix_recovery_read_error Ming Lei
2017-02-16 11:45 ` [PATCH 16/17] md: raid10: avoid direct access to bvec table in reshape_request Ming Lei
2017-02-16 11:45 ` [PATCH 17/17] md: raid10: avoid direct access to bvec table in handle_reshape_read_error Ming Lei
2017-02-16 22:16 ` [PATCH 00/17] md: cleanup on direct access to bvec table Shaohua Li
2017-02-17 1:25 ` Ming Lei
2017-02-17 4:16 ` Shaohua Li [this message]
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