From: "brian m. carlson" <sandals@crustytoothpaste•net>
To: Jeff King <peff@peff•net>
Cc: Junio C Hamano <gitster@pobox•com>,
Patrick Steinhardt <ps@pks•im>,
git@vger•kernel.org, Matt Smiley <msmiley@gitlab•com>
Subject: Re: [PATCH v2 05/10] compat/posix: introduce writev(3p) wrapper
Date: Thu, 5 Mar 2026 02:16:05 +0000 [thread overview]
Message-ID: <aajnZZI5yqL9CYeR@fruit.crustytoothpaste.net> (raw)
In-Reply-To: <20260305003745.GA4943@coredump.intra.peff.net>
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On 2026-03-05 at 00:37:45, Jeff King wrote:
> I like that writev() can work as a drop-in replacement for write() at
> the lowest level. But given that our main use is likely to be pkt-lines,
> I do kind of wonder if we should just try to be more clever in forming
> our buffers. That makes all of the portability and compat questions go
> away (and gives the benefit to platforms that don't even have writev).
This does work and it is clever, but I think the writev is clearer and
more explicit. In addition, this is literally the kind of use case that
it's designed for and the kernel will have a highly optimized
implementation handling it. I could also see myself making use of
writev in my future work as well, although I don't have any concrete
code depending on it at the moment (but I could probably add it in the
interop code).
There is a Windows equivalent as well (according to the Rust
documentation[0]) which doesn't have to be added at this point, but
could in the future as a quality-of-implementation issue. And almost
all Unix systems will support this, with the possible exception of
NonStop, since it's part of XSI and effectively everyone implements
those C functions. (Also, writev was in 4.2BSD, released in 1983, so
you'd have to be really behind the times to not support it.)
[0] Rust defines the `std::io::IoSlice` type which is documented as
follows:
A buffer type used with `Write::write_vectored`.
It is semantically a wrapper around a `&[u8]`, but is guaranteed to
be ABI compatible with the `iovec` type on Unix platforms and
`WSABUF` on Windows.
--
brian m. carlson (they/them)
Toronto, Ontario, CA
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next prev parent reply other threads:[~2026-03-05 2:16 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-27 11:22 [PATCH 0/2] upload-pack: reduce lock contention when writing packfile data Patrick Steinhardt
2026-02-27 11:23 ` [PATCH 1/2] upload-pack: fix debug statement when flushing " Patrick Steinhardt
2026-02-27 11:23 ` [PATCH 2/2] upload-pack: reduce lock contention when writing " Patrick Steinhardt
2026-02-27 13:04 ` brian m. carlson
2026-02-27 18:14 ` Patrick Steinhardt
2026-02-27 17:29 ` Junio C Hamano
2026-02-27 19:37 ` Jeff King
2026-03-02 12:12 ` Patrick Steinhardt
2026-03-02 18:20 ` Jeff King
2026-03-03 9:31 ` Patrick Steinhardt
2026-03-03 13:35 ` Jeff King
2026-03-03 13:47 ` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 00/10] " Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 01/10] upload-pack: fix debug statement when flushing " Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 02/10] upload-pack: adapt keepalives based on buffering Patrick Steinhardt
2026-03-05 0:56 ` Jeff King
2026-03-10 12:08 ` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 03/10] upload-pack: reduce lock contention when writing packfile data Patrick Steinhardt
2026-03-05 1:16 ` Jeff King
2026-03-10 12:14 ` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 04/10] git-compat-util: introduce `cast_size_t_to_ssize_t()` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 05/10] compat/posix: introduce writev(3p) wrapper Patrick Steinhardt
2026-03-04 22:01 ` Junio C Hamano
2026-03-05 0:37 ` Jeff King
2026-03-05 2:16 ` brian m. carlson [this message]
2026-03-05 6:39 ` Johannes Sixt
2026-03-05 22:22 ` brian m. carlson
2026-03-10 12:09 ` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 06/10] wrapper: introduce writev(3p) wrappers Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 07/10] sideband: use writev(3p) to send pktlines Patrick Steinhardt
2026-03-04 22:05 ` Junio C Hamano
2026-03-03 15:00 ` [PATCH v2 08/10] csum-file: introduce `hashfd_ext()` Patrick Steinhardt
2026-03-04 22:11 ` Junio C Hamano
2026-03-10 12:09 ` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 09/10] csum-file: drop `hashfd_throughput()` Patrick Steinhardt
2026-03-03 15:00 ` [PATCH v2 10/10] builtin/pack-objects: reduce lock contention when writing packfile data Patrick Steinhardt
2026-03-10 13:24 ` [PATCH v3 00/10] upload-pack: " Patrick Steinhardt
2026-03-10 13:24 ` [PATCH v3 01/10] upload-pack: fix debug statement when flushing " Patrick Steinhardt
2026-03-10 13:24 ` [PATCH v3 02/10] upload-pack: adapt keepalives based on buffering Patrick Steinhardt
2026-03-10 13:24 ` [PATCH v3 03/10] upload-pack: prefer flushing data over sending keepalive Patrick Steinhardt
2026-03-10 17:09 ` Junio C Hamano
2026-03-10 17:43 ` Patrick Steinhardt
2026-03-10 13:25 ` [PATCH v3 04/10] upload-pack: reduce lock contention when writing packfile data Patrick Steinhardt
2026-03-10 13:25 ` [PATCH v3 05/10] compat/posix: introduce writev(3p) wrapper Patrick Steinhardt
2026-03-10 16:59 ` Junio C Hamano
2026-03-10 13:25 ` [PATCH v3 06/10] wrapper: introduce writev(3p) wrappers Patrick Steinhardt
2026-03-10 13:25 ` [PATCH v3 07/10] sideband: use writev(3p) to send pktlines Patrick Steinhardt
2026-03-10 13:25 ` [PATCH v3 08/10] csum-file: introduce `hashfd_ext()` Patrick Steinhardt
2026-03-10 13:25 ` [PATCH v3 09/10] csum-file: drop `hashfd_throughput()` Patrick Steinhardt
2026-03-10 13:25 ` [PATCH v3 10/10] builtin/pack-objects: reduce lock contention when writing packfile data Patrick Steinhardt
2026-03-10 17:11 ` [PATCH v3 00/10] upload-pack: " Junio C Hamano
2026-03-10 20:56 ` Johannes Sixt
2026-03-11 6:27 ` Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 " Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 01/10] upload-pack: fix debug statement when flushing " Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 02/10] upload-pack: adapt keepalives based on buffering Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 03/10] upload-pack: prefer flushing data over sending keepalive Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 04/10] upload-pack: reduce lock contention when writing packfile data Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 05/10] compat/posix: introduce writev(3p) wrapper Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 06/10] wrapper: introduce writev(3p) wrappers Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 07/10] sideband: use writev(3p) to send pktlines Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 08/10] csum-file: introduce `hashfd_ext()` Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 09/10] csum-file: drop `hashfd_throughput()` Patrick Steinhardt
2026-03-13 6:45 ` [PATCH v4 10/10] builtin/pack-objects: reduce lock contention when writing packfile data Patrick Steinhardt
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