From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
"Martin K . Petersen" <martin.petersen@oracle.com>,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/2] block: integrity: enable multi-page bvec for bio integrity
Date: Wed, 24 Apr 2019 09:14:36 -0400 [thread overview]
Message-ID: <yq1ftq78s03.fsf@oracle.com> (raw)
In-Reply-To: <20190423071550.20806-2-ming.lei@redhat.com> (Ming Lei's message of "Tue, 23 Apr 2019 15:15:49 +0800")
Ming,
I'm traveling today and probably won't be able to take a closer look
until tomorrow. But from a quick glance this looks OK.
> The integrity buffer can't be very big, for example, the max sectors
> for one bio is 2560, one sector may take at most 8bytes for integrity
> info, so the max size of integrity buffer is just 20k(<=5 pages).
Just a comment on your rationale about 5 pages.
buffer_head submissions have traditionally been small, and depending on
your choice of allocator, new allocations would grow backwards in
memory. So there were several common I/O patterns that produced a
single, non-mergeable 8 byte integrity metadata allocation for every 512
bytes of data in the I/O. It's a pathological corner case. Just make
sure it's something you handle when you muck with this. ext[23] and dd
to the block device used to be able to reproduce this scenario easily.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2019-04-24 13:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-23 7:15 [PATCH 0/2] block: enable multi-page bvec for bio integrity Ming Lei
2019-04-23 7:15 ` [PATCH 1/2] block: integrity: " Ming Lei
2019-04-24 5:40 ` Christoph Hellwig
2019-04-24 13:14 ` Martin K. Petersen [this message]
2019-04-24 13:18 ` Ming Lei
2019-04-23 7:15 ` [PATCH 2/2] block: integrity: simplify bio_integrity_prep Ming Lei
2019-04-24 5:42 ` Christoph Hellwig
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