Date: Sun, 10 Mar 2002 14:51:58 +0200 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: "Simon 'corecode' Schubert" <corecode@corecode.ath.cx> Cc: freebsd-hackers@freebsd.org Subject: Re: Swapping performance Message-ID: <20020310125158.GA798@hades.hell.gr> In-Reply-To: <20020307164500.5dd21d16.corecode@corecode.ath.cx> References: <20020307090707.GC26621@elvis.mu.org> <Pine.BSF.4.21.0203070359110.41354-100000@InterJet.elischer.org> <20020307142759.0d95d467.mitko@rila.bg> <20020307080906.367be8df.gclarkii@vsservices.com> <20020307164724.D377@straylight.oblivion.bg> <20020307153615.GB1942@student.uu.se> <20020307164500.5dd21d16.corecode@corecode.ath.cx>
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On 2002-03-07 16:45, Simon 'corecode' Schubert wrote:
> to everybody who doesn't believe that: it really generates bad code.
> i've been having severe problems with my tcp and udp stack lately (on a
> i586/mmx machine). guess what, -O2 resulted in code which >>sometimes<<
> generated bad tcp and/or udp checksums (depending on ip). i didn't
> investigate any further, but believe me: not being able to access some
> dns servers is a pain in the ass.
I've seen this too. When I built both my kernel and userland with -O3,
problems accessing the Internet started. When I tried to use tcpdump to
find out what went wrong, I saw that it reported *all* outgoing packets for
*some* hosts as invalid [0xffff].
The funny thing was that depending on which source/destination I used, it
would either work or fail. For destinations that it failed once, it failed
all the time. Since I could not verify both the userland and kernel
binaries, I chose to disable most optimizations and stick with -O :-)
Giorgos Keramidas FreeBSD Documentation Project
keramida@{freebsd.org,ceid.upatras.gr} http://www.FreeBSD.org/docproj/
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