From 153934091c2c6f3e12ebbb7f242808407ee7eaf2 Mon Sep 17 00:00:00 2001 From: Gabor Pali Date: Sat, 14 Jun 2008 09:54:50 +0000 Subject: [PATCH] Update Question 4.2.2: - Rewrite from scratch by the aid of Release Notes Reviewed by: trhodes, danger, remko Approved by: gabor (mentor) --- en_US.ISO8859-1/books/faq/book.sgml | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/en_US.ISO8859-1/books/faq/book.sgml b/en_US.ISO8859-1/books/faq/book.sgml index eebbbd0f1b..81c6a7fd1d 100644 --- a/en_US.ISO8859-1/books/faq/book.sgml +++ b/en_US.ISO8859-1/books/faq/book.sgml @@ -2138,14 +2138,26 @@ - Yes. SMP was enabled by default in the - GENERIC kernel as of &os; 5.2. + Symmetric multi-processor (SMP) systems are generally + supported by &os;, although in some cases, BIOS or + motherboard bugs may generate some problems. Persuing + the &a.smp; may yield some clues. - The intention was also to enable it by default for - the &os; 5.3 release, but problems running the SMP kernel - on certain UP machines led to the decision to disable it - until those problems can be addressed. This is a priority - for &os; 5.4. + &os; will take advantage of HyperThreading (HTT) support + on Intel CPUs that support this feature. A kernel with the + options SMP feature enabled will + automatically detect the additional logical processors. The + default &os; scheduler treats the logical processors the + same as additional physical processors; in other words, no + attempt is made to optimize scheduling decisions given the + shared resources between logical processors within the same + CPU. Because this naive scheduling can result in suboptimal + performance, under certain circumstances it may be useful to + disable the logical processors with the + machdep.hlt_logical_cpus sysctl variable. + It is also possible to halt any CPU in the idle loop with + the machdep.hlt_cpus sysctl variable. + The &man.smp.4; manual page has more details.