Date: Tue, 25 Nov 2003 01:17:34 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: peterjeremy@optushome.com.au Cc: gallatin@cs.duke.edu Subject: Re: 40% slowdown with dynamic /bin/sh Message-ID: <20031125.011734.118629079.imp@bsdimp.com> In-Reply-To: <20031125080155.GC76478@server.vk2pj.dyndns.org> References: <200311242125.13786.sam@errno.com> <20031124.231607.128865107.imp@bsdimp.com> <20031125080155.GC76478@server.vk2pj.dyndns.org>
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Peter Jeremy <peterjeremy@optushome.com.au> writes:
: On Mon, Nov 24, 2003 at 11:16:07PM -0700, M. Warner Losh wrote:
: >Hmmmm, It looks like the hit is less than 10% in the fork intensive
: >test I just wrote:
: >
: >#!/bin/sh
: >for i in 0 1 2 3 4 5 6 7 8 9; do
: > for j in 0 1 2 3 4 5 6 7 8 9; do
: > for k in 0 1 2 3 4 5 6 7 8 9; do
: > for l in 0 1 2 3 4 5 6 7 8 9; do
: > for m in 0 1 2 3 4 5 6 7 8 9; do
: > for n in 0 1 2 3 4 5 6 7 8 9; do
: > true;
: >done; done; done; done; done; done;
:
: Unless you've done something wierd to your /bin/sh, "true" is a
: builtin. This test just to measures the ongoing runtime overhead
: of a dynamic executable (ie PIC code). Drew's test was measuring
: the startup overhead.
True. However, I get very similar numbers of I change it to
/usr/bin/true (12% slower). /bin/sh usually fork+exec things other
/bin/sh.
: >Clearly dynamic is slower, but it is more like 11% slower (10.67%) on
: >the average than 40% slower. I think this would be a more typical
: >usage pattern.
:
: You have measured different things. Drew's test shows that a dynamic
: /bin/sh tahes about 40% longer to start. Your test shows that once
: started, it runs about 11% slower. And the 11% slower is _very_
: worrying since it is probably more widely applicable than just /bin/sh.
Dynamically linked prorgrams tend to be a few percent slower than
their static counterparts due to PIC code typically being slower than
non-PIC code. There's nothing new here.
Clearly there are problems to look into, but it isn't the end of the
world.
Warner
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