Date: Sun, 10 Nov 2002 16:53:17 -0500 From: Don Bowman <don@sandvine.com> To: "'freebsd-hackers@freebsd.org'" <freebsd-hackers@freebsd.org> Subject: stack alignment, XEON / P4 Message-ID: <FE045D4D9F7AED4CBFF1B3B813C8533701022EC7@mail.sandvine.com>
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In sys/conf/kern.mk, there is a comment about not aligning
the (x86) stack to 16-byte boundaries, and it overrides the
preferred-stack-boundary to 2.
.if ${MACHINE_ARCH} == "i386"
CFLAGS+= -mno-align-long-strings -mpreferred-stack-boundary=2
.endif
This seems to be contradicted by intel's optimisation guide
for the P4/XEON family.
It seems that the performance is best by making it 4, even for
older chips.
Is there any hidden pitfall to changing this value? I compiled
a kernel, and all seems to run ok.
--don (don@sandvine.com www.sandvine.com)
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