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Date: Tue, 28 Nov 2017 18:12:02 +0100
From: Houder <houder@xs4all.nl>
To: cygwin@cygwin.com
Cc: djndnbvg@gmail.com
Subject: Re: sort utility goes berzerk (x86_64)
In-Reply-To: <CAJ1FpuMVeneyhKmv0d8J_EPXjfrJ09FpVt=ojMEeJPRLyKes=A@mail.gmail.com>
References: <177e9f9fe723eadd4a8e41e5e032d56d@smtp-cloud9.xs4all.net> <eeee637eb6e6b01641d33930e178cbae@xs4all.nl> <20171128090329.GN547@calimero.vinschen.de> <09fc4a030cc7abb5cabf07672e683d70@xs4all.nl> <CAJ1FpuMVeneyhKmv0d8J_EPXjfrJ09FpVt=ojMEeJPRLyKes=A@mail.gmail.com>
Message-ID: <944c377d08d67cda987edfcf4389ee89@xs4all.nl>
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On 2017-11-28 14:37, Doug Henderson wrote:

>>>> On 2017-11-25 14:23, Houder wrote:
>>>> > Hi,
>>>> >
>>>> > Anyone seeing this as well? sort goes berzerk on my system when piped
>>>> > into
>>>> > head (or less) when it is fed with a 'specially prepared' input file.
>>>> >
>>>> >  - only happens on x86_64
>>>> >  - does not happen for 'LC_COLLATE=C sort tt | head'
>>>> >
>>>> > 'specially prepared' input file? (see bottom of post).
>>>> 
>>>> Anyone ** NOT ** seeing this?

> Q4. After you kill a hung sort, are there files left over in /tmp? I
> am wondering if the problem files are too big to do an in-core sort,
> and something goes wrong when it switches to a temp file sort, but not
> for smaller or larger input files where it correctly predicts which
> type of sort it needs to do. Possibly using the "--buffer-size=N"
> option will change the behavior, making smaller input files fail and
> failing ones work.

Preliminary result:

# tt = 8150 lines
sort -S 1024 tt | head # 1024 * 1024 = 1M
sort -S 1152 tt | head # + 128
sort -S 1280 tt | head # + 256 <==== fail (1226?)

# ttt = 5050 lines
sort -S 512 ttt | head # 512 * 1024 = .5M
sort -S 640 ttt | head # + 128
sort -S 768 ttt | head # + 256 <==== fail (760?)

These numbers are correct for --parallel=8 (the eight "cores" that are
in my machine)

Specifying a smaller number of cores, also make the above numbers grow
smaller.

All of the above is about tuning the performance of sort; however it is
not an explanation for the way in which sort fails.

sort should not fail in the way it does; it does not on "Cygwin/x86" on
my machine; it does not on Linux (Fedora 24) (same machine).


Henri

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