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From: Eric Sunshine <sunshine@sunshineco.com>
To: Alexandr Miloslavskiy via GitGitGadget <gitgitgadget@gmail.com>
Cc: Git List <git@vger.kernel.org>,
	Paul-Sebastian Ungureanu <ungureanupaulsebastian@gmail.com>,
	Erik Faye-Lund <kusmabite@gmail.com>,
	Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Subject: Re: [PATCH] mingw: workaround for hangs when sending STDIN
Date: Thu, 13 Feb 2020 13:56:37 -0500	[thread overview]
Message-ID: <CAPig+cQrxKuE=a99zPF7EGUSbye_s5ATEvUkz+EqsTZAfy_CbQ@mail.gmail.com> (raw)
In-Reply-To: <pull.553.git.1581619239467.gitgitgadget@gmail.com>

On Thu, Feb 13, 2020 at 1:40 PM Alexandr Miloslavskiy via GitGitGadget
<gitgitgadget@gmail.com> wrote:
> 3) Make `poll()` always reply "writable" for write end of the pipe
>    Afterall it seems that cygwin (accidentally?) does that for years.
>    Also, it should be noted that `pump_io_round()` writes 8MB blocks,
>    completely ignoring the fact that pipe's buffer size is only 8KB,
>    which means that pipe gets clogged many times during that single
>    write. This may invite a deadlock, if child's STDERR/STDOUT gets
>    clogged while it's trying to deal with 8MB of STDIN. Such deadlocks
>    could  be defeated with writing less then pipe's buffer size per

s/then/than/

>    round, and always reading everything from STDOUT/STDERR before
>    starting next round. Therefore, making `poll()` always reply
>    "writable" shouldn't cause any new issues or block any future
>    solutions.
> 4) Increase the size of the pipe's buffer
>    The difference between `BytesInQueue` and `QuotaUsed` is the size
>    of pending reads. Therefore, if buffer is bigger then size of reads,

s/then/than/

>    `poll()` won't hang so easily. However, I found that for example
>    `strbuf_read()` will get more and more hungry as it reads large inputs,
>    eventually surpassing any reasonable pipe buffer size.
> diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
> +test_expect_success 'stash handles large files' '
> +       printf "%1023s\n%.0s" "x" {1..16384} >large_file.txt &&
> +       git stash push --include-untracked -- large_file.txt
> +'

Use of {1..16384} is not portable across shells. You should be able to
achieve something similar by assigning a really large value to a shell
variable and then echoing that value to "large_file.txt". Something
like:

    x=0123456789
    x=$x$x$x$x$x$x$x$x$x$x
    x=$x$x$x$x$x$x$x$x$x$x
    ...and so on...
    echo $x >large_file.txt &&

or any other similar construct.

  parent reply	other threads:[~2020-02-13 18:56 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13 18:40 [PATCH] mingw: workaround for hangs when sending STDIN Alexandr Miloslavskiy via GitGitGadget
2020-02-13 18:41 ` Test program used to prove quota's behavior Alexandr Miloslavskiy
2020-02-13 18:56 ` Eric Sunshine [this message]
2020-02-13 19:22   ` [PATCH] mingw: workaround for hangs when sending STDIN Alexandr Miloslavskiy
2020-02-17 16:25 ` [PATCH v2] " Alexandr Miloslavskiy via GitGitGadget
2020-02-17 17:24   ` Eric Sunshine
2020-02-17 17:56     ` Junio C Hamano
2020-02-17 18:01     ` Alexandr Miloslavskiy
2020-02-17 18:01   ` [PATCH v3] " Alexandr Miloslavskiy via GitGitGadget
2020-02-18 16:39     ` Junio C Hamano
2020-02-27 21:15       ` Johannes Schindelin
2020-02-27 22:59         ` Junio C Hamano

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