From: Al Viro <viro@zeniv.linux.org.uk>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org, torvalds@linux-foundation.org,
brauner@kernel.org
Subject: Re: [PATCH 3/3] iov_iter: import single vector iovecs as ITER_UBUF
Date: Tue, 28 Mar 2023 01:08:11 +0100 [thread overview]
Message-ID: <20230328000811.GJ3390869@ZenIV> (raw)
In-Reply-To: <20230327232713.313974-4-axboe@kernel.dk>
On Mon, Mar 27, 2023 at 05:27:13PM -0600, Jens Axboe wrote:
> Add a special case to __import_iovec(), which imports a single segment
> iovec as an ITER_UBUF rather than an ITER_IOVEC. ITER_UBUF is cheaper
> to iterate than ITER_IOVEC, and for a single segment iovec, there's no
> point in using a segmented iterator.
Won't that enforce the "single-segment readv() is always identical to
read()"? We'd been through that before - some of infinibarf drvivers
have two different command sets, one reached via read(), another - via
readv(). It's a userland ABI. Misdesigned one, but that's infinibarf
for you.
Does anyone really need this particular microoptimization?
next prev parent reply other threads:[~2023-03-28 0:08 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-27 23:27 [PATCHSET v3 0/4] Turn single segment imports into ITER_UBUF Jens Axboe
2023-03-27 23:27 ` [PATCH 1/3] iov_iter: teach iov_iter_iovec() to deal with ITER_UBUF Jens Axboe
2023-03-27 23:27 ` [PATCH 2/3] iov_iter: convert import_single_range() to ITER_UBUF Jens Axboe
2023-03-27 23:27 ` [PATCH 3/3] iov_iter: import single vector iovecs as ITER_UBUF Jens Axboe
2023-03-28 0:08 ` Al Viro [this message]
2023-03-28 0:25 ` Al Viro
2023-03-28 1:20 ` Jens Axboe
2023-03-28 13:20 ` Jens Axboe
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