linux-kernel - RE: [patch 0/3] no MAX_ARG

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Message-ID: <617E1C2C70743745A92448908E030B2A01AF860A@scsmsx411.amr.corp.intel.com>
Date:	Wed, 13 Jun 2007 16:36:13 -0700
From:	"Luck, Tony" <tony.luck@...el.com>
To:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	<linux-kernel@...r.kernel.org>,
	<parisc-linux@...ts.parisc-linux.org>, <linux-mm@...ck.org>,
	<linux-arch@...r.kernel.org>
Cc:	"Ollie Wild" <aaw@...gle.com>, "Andrew Morton" <akpm@...l.org>,
	"Ingo Molnar" <mingo@...e.hu>, "Andi Kleen" <ak@...e.de>
Subject: RE: [patch 0/3] no MAX_ARG_PAGES -v2

> This patch-set aims at removing the current limit on argv+env space aka.
> MAX_ARG_PAGES.

Running with this patch shows that /bin/bash has some unpleasant
O(n^2) performance issues with long argument lists.  I made a
1Mbyte file full of pathnames, then timed the execution of:

$ /bin/echo `cat megabyte` | wc
$ /bin/echo `cat megabyte megabyte` | wc
   etc. ...

System time was pretty much linear as the arglist grew
(and only got up to 0.144 seconds at 5Mbytes).

But user time ~= real time (in seconds) looks like:

1 5.318
2 18.871
3 40.620
4 70.819
5 108.911

Above 5Mbytes, I started seeing problems.  The line/word/char
counts from "wc" started being "0 0 0".  Not sure if this is
a problem in "wc" dealing with a single line >5MBytes, or some
other problem (possibly I was exceeding the per-process stack
limit which is only 8MB on that machine).

-Tony
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