Messages in this thread | | | Date | Sat, 4 Jan 2003 19:35:17 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [BENCHMARK] Lmbench 2.5.54-mm2 (impressive improvements) |
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On Sat, 4 Jan 2003, Andrew Morton wrote: > > Looks like you're right. The indications are that this change > has slowed context switches by ~5% on a PIII. The backout patch > against 2.5.54 is below. Testing on a P4 would be useful.
Hmm.. The backup patch doesn't handle single-stepping correctly: the eflags cleanup singlestep patch later in the sysenter sequence _depends_ on the stack (and thus thread) being right on the very first in-kernel instruction.
That (along with benchmarking of system call numbers - the stack switch at system call run-time ends up being quite expensive on a P4) was what made me decide to do the traditional "write MSR in schedule" approach, even though I agree that it would be much nicer to not have to rewrite that stupid MSR all the time.
It doesn't show up on lmbench (insufficient precision), but your AIM9 numbers are quite interesting. Are they stable?
Linus
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