Date: Wed, 28 Nov 2007 23:24:07 +0000 (UTC) From: Colin Percival <cperciva@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/amd64/amd64 mp_machdep.c src/sys/i386/i386 mp_machdep.c Message-ID: <200711282324.lASNO75D058717@repoman.freebsd.org>
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cperciva 2007-11-28 23:24:07 UTC
FreeBSD src repository
Modified files: (Branch: RELENG_7)
sys/amd64/amd64 mp_machdep.c
sys/i386/i386 mp_machdep.c
Log:
Back out previous commit; i.e., turn hyperthreading back on by default.
Newer Intel processors have better hyperthreading implementations than
the original ones, and FreeBSD's SMP and scheduler code has greatly
improved between 6.x and 7.x; so hyperthreading now provides a
non-trivial performance win.
Note that security issues involving shared caches and other
microarchitectural features (e.g., dynamic branch prediction tables)
still exist; consequently, it is recommended that hyperthreading be
turned off on systems with untrusted local users. This can be
performed by setting machdep.hyperthreading_allowed=0 in
/boot/loader.conf.
Hyperthreading will continue to be disabled by default on FreeBSD 6.x.
Requested by: core
Approved by: re (kensmith)
Security: See FreeBSD-SA-05:09.htt for background information.
Revision Changes Path
1.287.2.2 +1 -1 src/sys/amd64/amd64/mp_machdep.c
1.281.2.2 +1 -1 src/sys/i386/i386/mp_machdep.c
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