From: Jeff King <peff@peff.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: Jiang Xin <worldhello.net@gmail.com>,
Taylor Blau <me@ttaylorr.com>, Git List <git@vger.kernel.org>,
Kyle Zhao <kylezhao@tencent.com>,
Jiang Xin <zhiyou.jx@alibaba-inc.com>
Subject: Re: [PATCH] t5516: fail to run in verbose mode
Date: Mon, 28 Nov 2022 00:13:52 -0500 [thread overview]
Message-ID: <Y4RDkGZE3cZFS25d@coredump.intra.peff.net> (raw)
In-Reply-To: <xmqqzgcfeik0.fsf@gitster.g>
On Fri, Nov 25, 2022 at 01:58:55PM +0900, Junio C Hamano wrote:
> Jeff King <peff@peff.net> writes:
>
> > One thing I'd worry about is buffering. One of the nice things about
> > "-v" is that there is nothing between you and the running programs, so
> > you are much less likely to be fooled about the order of events in the
> > output. Or wondering why nothing is happening because real-time output
> > seems to have stalled. But piping through "cat" may end up with weird
> > pauses while it fills up a 4k buffer. Using stdbuf could help, but
> > that's far from portable.
>
> We could pipe to "dd bs=1 conv=fsync" (tongue-in-cheek---I think
> conv=fsync is a GNU thing).
We don't need the fsync; we are just worried about in-process buffering,
not kernel-level flushing. So bs=1 is sufficient, in that it would
use syscalls to read/write single bytes. It would just be horribly
inefficient.
We really just want immediate partial read()/write() but with sensible
buffer sizes. It would be easy to write a 5-line C program that did this
if we really wanted to. I'm not entirely convinced it's worth worrying
too much about, though.
-Peff
prev parent reply other threads:[~2022-11-28 5:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-21 13:40 [PATCH] t5516: fail to run in verbose mode Jiang Xin
2022-11-22 2:22 ` [Internet][PATCH] " kylezhao(赵柯宇)
2022-11-22 4:19 ` [PATCH] " Junio C Hamano
2022-11-22 19:08 ` Jeff King
2022-11-23 1:17 ` Junio C Hamano
2022-11-24 1:16 ` Jeff King
2022-11-25 4:58 ` Junio C Hamano
2022-11-28 5:13 ` Jeff King [this message]
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