From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [RFC PATCH 2/2] block: split bio if the only bvec's length is > SZ_4K
Date: Mon, 11 Nov 2019 11:21:59 +0100 [thread overview]
Message-ID: <20191111102159.GA12709@lst.de> (raw)
In-Reply-To: <20191108101528.31735-3-ming.lei@redhat.com>
On Fri, Nov 08, 2019 at 06:15:28PM +0800, Ming Lei wrote:
> 64K PAGE_SIZE is popular on ARM64 or other ARCHs, and 64K has been big
> enough to break some devices probably, so change the logic to split bio
> if the only bvec's length is > SZ_4K instead of PAGE_SIZE.
I don't think this makes sense as-is given that blk_queue_max_hw_sectors,
blk_queue_max_segment_size and co all check for a minimum of PAGE_SIZE
and warn otherwise, and blk_bio_segment_split uses PAGE_SIZE for
its short cut as well. So I don't think this has been a problem in
practice, and if it was this patch is not enough.
So either we leave things as is, or we need to do a real audit for
code using PAGE_SIZE as the minimum I/O granularity and replace it
everywhere a well as updating the documentation. Which might be a good
thing given that variable sized limits are weird.
next prev parent reply other threads:[~2019-11-11 10:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-08 10:15 [PATCH 0/2] block: two fixes on avoiding bio splitting Ming Lei
2019-11-08 10:15 ` [PATCH 1/2] block: still try to split bio if the bvec crosses pages Ming Lei
2019-11-08 10:15 ` [RFC PATCH 2/2] block: split bio if the only bvec's length is > SZ_4K Ming Lei
2019-11-11 10:21 ` Christoph Hellwig [this message]
2019-11-08 14:00 ` [PATCH 0/2] block: two fixes on avoiding bio splitting Jens Axboe
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