From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Theodore Ts'o <tytso@mit.edu>,
Omar Sandoval <osandov@fb.com>, Sagi Grimberg <sagi@grimberg.me>,
Dave Chinner <dchinner@redhat.com>,
Kent Overstreet <kent.overstreet@gmail.com>,
Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Shaohua Li <shli@kernel.org>,
linux-raid@vger.kernel.org, David Sterba <dsterba@suse.com>,
linux-btrfs@vger.kernel.org,
"Darrick J . Wong" <darrick.wong@oracle.com>,
linux-xfs@vger.kernel.org, Gao Xiang <gaoxiang25@huawei.com>,
linux-ext4@vger.kernel.org, Coly Li <colyli@suse.de>,
linux-bcache@vger.kernel.org, Boaz Harrosh <oo>
Subject: Re: [PATCH V11 14/19] block: handle non-cluster bio out of blk_bio_segment_split
Date: Thu, 22 Nov 2018 11:04:28 +0100 [thread overview]
Message-ID: <20181122100427.GA28871@lst.de> (raw)
In-Reply-To: <20181122093259.GA27007@ming.t460p>
On Thu, Nov 22, 2018 at 05:33:00PM +0800, Ming Lei wrote:
> However, using virt boundary limit on non-cluster seems over-kill,
> because the bio will be over-split(each small bvec may be split as one bio)
> if it includes lots of small segment.
The combination of the virt boundary of PAGE_SIZE - 1 and a
max_segment_size of PAGE_SIZE will only split if the to me merged
segment is in a different page than the previous one, which is exactly
what we need here. Multiple small bvec inside the same page (e.g.
512 byte buffer_heads) will still be merged.
> What we want to do is just to avoid to merge bvecs to segment, which
> should have been done by NO_SG_MERGE simply. However, after multi-page
> is enabled, two adjacent bvecs won't be merged any more, I just forget
> to remove the bvec merge code in V11.
>
> So seems we can simply avoid to use virt boundary limit for non-cluster
> after multipage bvec is enabled?
No, we can't just remove it. As explained in the patch there is one very
visible difference of setting the flag amd that is no segment will span a
page boundary, and at least the iSCSI code seems to rely on that.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Theodore Ts'o <tytso@mit.edu>,
Omar Sandoval <osandov@fb.com>, Sagi Grimberg <sagi@grimberg.me>,
Dave Chinner <dchinner@redhat.com>,
Kent Overstreet <kent.overstreet@gmail.com>,
Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Shaohua Li <shli@kernel.org>,
linux-raid@vger.kernel.org, David Sterba <dsterba@suse.com>,
linux-btrfs@vger.kernel.org,
"Darrick J . Wong" <darrick.wong@oracle.com>,
linux-xfs@vger.kernel.org, Gao Xiang <gaoxiang25@huawei.com>,
linux-ext4@vger.kernel.org, Coly Li <colyli@suse.de>,
linux-bcache@vger.kernel.org, Boaz Harrosh <ooo@electrozaur.com>,
Bob Peterson <rpeterso@redhat.com>,
cluster-devel@redhat.com
Subject: Re: [PATCH V11 14/19] block: handle non-cluster bio out of blk_bio_segment_split
Date: Thu, 22 Nov 2018 11:04:28 +0100 [thread overview]
Message-ID: <20181122100427.GA28871@lst.de> (raw)
In-Reply-To: <20181122093259.GA27007@ming.t460p>
On Thu, Nov 22, 2018 at 05:33:00PM +0800, Ming Lei wrote:
> However, using virt boundary limit on non-cluster seems over-kill,
> because the bio will be over-split(each small bvec may be split as one bio)
> if it includes lots of small segment.
The combination of the virt boundary of PAGE_SIZE - 1 and a
max_segment_size of PAGE_SIZE will only split if the to me merged
segment is in a different page than the previous one, which is exactly
what we need here. Multiple small bvec inside the same page (e.g.
512 byte buffer_heads) will still be merged.
> What we want to do is just to avoid to merge bvecs to segment, which
> should have been done by NO_SG_MERGE simply. However, after multi-page
> is enabled, two adjacent bvecs won't be merged any more, I just forget
> to remove the bvec merge code in V11.
>
> So seems we can simply avoid to use virt boundary limit for non-cluster
> after multipage bvec is enabled?
No, we can't just remove it. As explained in the patch there is one very
visible difference of setting the flag amd that is no segment will span a
page boundary, and at least the iSCSI code seems to rely on that.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: cluster-devel.redhat.com
Subject: [Cluster-devel] [PATCH V11 14/19] block: handle non-cluster bio out of blk_bio_segment_split
Date: Thu, 22 Nov 2018 11:04:28 +0100 [thread overview]
Message-ID: <20181122100427.GA28871@lst.de> (raw)
In-Reply-To: <20181122093259.GA27007@ming.t460p>
On Thu, Nov 22, 2018 at 05:33:00PM +0800, Ming Lei wrote:
> However, using virt boundary limit on non-cluster seems over-kill,
> because the bio will be over-split(each small bvec may be split as one bio)
> if it includes lots of small segment.
The combination of the virt boundary of PAGE_SIZE - 1 and a
max_segment_size of PAGE_SIZE will only split if the to me merged
segment is in a different page than the previous one, which is exactly
what we need here. Multiple small bvec inside the same page (e.g.
512 byte buffer_heads) will still be merged.
> What we want to do is just to avoid to merge bvecs to segment, which
> should have been done by NO_SG_MERGE simply. However, after multi-page
> is enabled, two adjacent bvecs won't be merged any more, I just forget
> to remove the bvec merge code in V11.
>
> So seems we can simply avoid to use virt boundary limit for non-cluster
> after multipage bvec is enabled?
No, we can't just remove it. As explained in the patch there is one very
visible difference of setting the flag amd that is no segment will span a
page boundary, and at least the iSCSI code seems to rely on that.
next prev parent reply other threads:[~2018-11-22 10:04 UTC|newest]
Thread overview: 177+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-21 3:23 [PATCH V11 00/19] block: support multi-page bvec Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 01/19] block: don't use bio->bi_vcnt to figure out segment number Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 02/19] block: introduce multi-page bvec helpers Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 13:19 ` Christoph Hellwig
2018-11-21 13:19 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 13:19 ` Christoph Hellwig
2018-11-21 15:06 ` Ming Lei
2018-11-21 15:06 ` [Cluster-devel] " Ming Lei
2018-11-21 15:06 ` Ming Lei
2018-11-21 16:08 ` Christoph Hellwig
2018-11-21 16:08 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 16:08 ` Christoph Hellwig
2018-11-22 1:09 ` Ming Lei
2018-11-22 1:09 ` [Cluster-devel] " Ming Lei
2018-11-22 1:09 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 03/19] block: introduce bio_for_each_bvec() Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 13:32 ` Christoph Hellwig
2018-11-21 13:32 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 13:32 ` Christoph Hellwig
2018-11-21 15:31 ` Ming Lei
2018-11-21 15:31 ` [Cluster-devel] " Ming Lei
2018-11-21 15:31 ` Ming Lei
2018-11-21 16:10 ` Christoph Hellwig
2018-11-21 16:10 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 16:10 ` Christoph Hellwig
2018-11-21 17:12 ` Christoph Hellwig
2018-11-21 17:12 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 17:12 ` Christoph Hellwig
2018-11-22 10:15 ` Ming Lei
2018-11-22 10:15 ` [Cluster-devel] " Ming Lei
2018-11-22 10:15 ` Ming Lei
2018-11-22 10:23 ` Christoph Hellwig
2018-11-22 10:23 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:23 ` Christoph Hellwig
2018-11-22 10:30 ` Christoph Hellwig
2018-11-22 10:30 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:30 ` Christoph Hellwig
2018-11-22 14:57 ` Ming Lei
2018-11-22 14:57 ` [Cluster-devel] " Ming Lei
2018-11-22 14:57 ` Ming Lei
2018-11-22 1:17 ` Ming Lei
2018-11-22 1:17 ` [Cluster-devel] " Ming Lei
2018-11-22 1:17 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 04/19] block: use bio_for_each_bvec() to compute multi-page bvec count Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 05/19] block: use bio_for_each_bvec() to map sg Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 06/19] block: introduce bvec_last_segment() Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 07/19] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-22 10:58 ` Christoph Hellwig
2018-11-22 10:58 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:58 ` Christoph Hellwig
2018-11-23 1:48 ` Ming Lei
2018-11-23 1:48 ` [Cluster-devel] " Ming Lei
2018-11-23 1:48 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 08/19] btrfs: use bvec_last_segment to get bio's last page Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 09/19] btrfs: move bio_pages_all() to btrfs Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 10/19] block: loop: pass multi-page bvec to iov_iter Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 14:00 ` Christoph Hellwig
2018-11-21 14:00 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 14:00 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 11/19] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 14:01 ` Christoph Hellwig
2018-11-21 14:01 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 14:01 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 12/19] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 14:02 ` Christoph Hellwig
2018-11-21 14:02 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 14:02 ` Christoph Hellwig
2018-11-22 11:03 ` Christoph Hellwig
2018-11-22 11:03 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 11:03 ` Christoph Hellwig
2018-11-23 2:19 ` Ming Lei
2018-11-23 2:19 ` [Cluster-devel] " Ming Lei
2018-11-23 2:19 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 13/19] block: move bounce_clone_bio into bio.c Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 14/19] block: handle non-cluster bio out of blk_bio_segment_split Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 14:33 ` Christoph Hellwig
2018-11-21 14:33 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 14:33 ` Christoph Hellwig
2018-11-21 15:37 ` Ming Lei
2018-11-21 15:37 ` [Cluster-devel] " Ming Lei
2018-11-21 15:37 ` Ming Lei
2018-11-21 16:11 ` Christoph Hellwig
2018-11-21 16:11 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 16:11 ` Christoph Hellwig
2018-11-21 17:46 ` Christoph Hellwig
2018-11-21 17:46 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 17:46 ` Christoph Hellwig
2018-11-21 17:46 ` Christoph Hellwig
2018-11-21 17:46 ` Christoph Hellwig
2018-11-22 9:33 ` Ming Lei
2018-11-22 9:33 ` [Cluster-devel] " Ming Lei
2018-11-22 9:33 ` Ming Lei
2018-11-22 10:04 ` Christoph Hellwig [this message]
2018-11-22 10:04 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:04 ` Christoph Hellwig
2018-11-22 10:26 ` Ming Lei
2018-11-22 10:26 ` [Cluster-devel] " Ming Lei
2018-11-22 10:26 ` Ming Lei
2018-11-22 10:40 ` Christoph Hellwig
2018-11-22 10:40 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:40 ` Christoph Hellwig
2018-11-22 10:32 ` Ming Lei
2018-11-22 10:32 ` [Cluster-devel] " Ming Lei
2018-11-22 10:32 ` Ming Lei
2018-11-22 10:41 ` Christoph Hellwig
2018-11-22 10:41 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:41 ` Christoph Hellwig
2018-11-22 10:46 ` Ming Lei
2018-11-22 10:46 ` [Cluster-devel] " Ming Lei
2018-11-22 10:46 ` Ming Lei
2018-11-22 10:47 ` Christoph Hellwig
2018-11-22 10:47 ` [Cluster-devel] " Christoph Hellwig
2018-11-22 10:47 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 15/19] block: enable multipage bvecs Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 14:55 ` Christoph Hellwig
2018-11-21 14:55 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 14:55 ` Christoph Hellwig
2018-11-21 15:48 ` Ming Lei
2018-11-21 15:48 ` [Cluster-devel] " Ming Lei
2018-11-21 15:48 ` Ming Lei
2018-11-21 16:12 ` Christoph Hellwig
2018-11-21 16:12 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 16:12 ` Christoph Hellwig
2018-11-23 10:50 ` Ming Lei
2018-11-23 10:50 ` [Cluster-devel] " Ming Lei
2018-11-23 10:50 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 16/19] block: always define BIO_MAX_PAGES as 256 Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 17/19] block: document usage of bio iterator helpers Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 7:45 ` Nikolay Borisov
2018-11-21 7:45 ` [Cluster-devel] " Nikolay Borisov
2018-11-21 7:45 ` Nikolay Borisov
2018-11-21 7:45 ` Nikolay Borisov
2018-11-21 14:34 ` Christoph Hellwig
2018-11-21 14:34 ` [Cluster-devel] " Christoph Hellwig
2018-11-21 14:34 ` Christoph Hellwig
2018-11-21 3:23 ` [PATCH V11 18/19] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
2018-11-21 3:23 ` [PATCH V11 19/19] block: kill BLK_MQ_F_SG_MERGE Ming Lei
2018-11-21 3:23 ` [Cluster-devel] " Ming Lei
2018-11-21 3:23 ` Ming Lei
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