Messages in this thread |  | | Date | Mon, 10 Mar 2003 12:06:35 +0100 | From | Andi Kleen <> | Subject | Re: [Bug 350] New: i386 context switch very slow compared to 2.4 due to wrmsr (performance) |
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On Mon, Mar 10, 2003 at 04:07:36AM +0100, Linus Torvalds wrote: > since you've been interested in the past, I thought I'd ask you to test > the current context switch stuff. Andi cleaned up some FPU reload stuff > (and I fixed a bug in it, tssk tssk Andi - you'd obviously not actually > timed your cleanups), and I just committed and pushed out my "cache the
You mean the TIF->_TIF thing? Yes that was wrong in the first patch, but fixed in the patches later. Unfortunately the patch still has the problem pointed out by Manfred Spraul: if you're unlucky it could destroy the _TIF_SIGPENDING set by another CPU with the non atomic access. Really thread_info should have two flag words: one that is truly local and can be accessed without LOCK and one that can be changed at will by external users too.
After some discussion with him I think the right fix for now is to move it it back to PF_USEDFPU into task_struct->flags.
Will submit a patch for that later after I was able to test it.
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