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Date:      Mon, 18 Dec 2000 12:22:43 -0700
From:      Warner Losh <imp@village.org>
To:        Matt Dillon <dillon@earth.backplane.com>
Cc:        "Jacques A. Vidrine" <n@nectar.com>, hackers@FreeBSD.ORG
Subject:   Re: Why not another style thread? (was Re: cvs commit: src/lib/libc/gen getgrent.c) 
Message-ID:  <200012181922.MAA93045@harmony.village.org>
In-Reply-To: Your message of "Mon, 18 Dec 2000 10:59:12 PST." <200012181859.eBIIxCS46046@earth.backplane.com> 
References:  <200012181859.eBIIxCS46046@earth.backplane.com>  <20001218123108.A65143@hamlet.nectar.com> <20001217170316.A63227@hamlet.nectar.com> <200012172110.eBHLAfU46563@freefall.freebsd.org> <20001217151509.A63051@hamlet.nectar.com> <20001217151735.D54486@holly.calldei.com> <20001217153129.B63080@hamlet.nectar.com> <20001217153656.F54486@holly.calldei.com> <20001217155648.C63080@hamlet.nectar.com> <20001217160442.H54486@holly.calldei.com> <20001217170316.A63227@hamlet.nectar.com> <200012180501.WAA87838@harmony.village.org> <200012181840.LAA92561@harmony.village.org> 

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In message <200012181859.eBIIxCS46046@earth.backplane.com> Matt Dillon writes:
:     Optimizations have two sides to them.  On the one hand they can make
:     code go faster.  On the otherhand they can turn once-readable code into
:     a tangle.  The rule of thumb is:  If the optimization has no measureable
:     effect on the programs you expect to run in a system, don't do it.

Agreed.  It is like teaching a pig to sing.  It only annoys you and
frustrates the pig :-).  Engineering effort is better spend on those
parts of the system that take up the most amount of time in your
profiles.  Otherwise no one will notice.

:     Case in point: the TCP stack.  Just *try* reading it!

Agreed.  Except back in the dim, dark past the tcp stack did show a
rather substantial improvement with the optimizations done to it.  I
think it was called "fast path" coding where the most common case was
made a special case at the top of the loop.

Warner


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