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Date: Wed, 06 Sep 2006 07:19:19 -0700 From: Daniel Walker <dwalker@...sta.com> To: Ingo Molnar <mingo@...e.hu> Cc: Hua Zhong <hzhong@...il.com>, 'Heiko Carstens' <heiko.carstens@...ibm.com>, 'Andrew Morton' <akpm@...l.org>, linux-kernel@...r.kernel.org, 'Arjan van de Ven' <arjan@...radead.org> Subject: Re: lockdep oddity On Wed, 2006-09-06 at 10:40 +0200, Ingo Molnar wrote: > * Hua Zhong <hzhong@...il.com> wrote: > > > We are just trading accuracy for speed here. > > no, we are trading _both_ accuracy and speed here! a global 'likeliness' > pointer for commonly executed codepaths is causing global cacheline > ping-pongs - which is as bad as it gets. Up stream or no, would be better for it to again be light weight. > the right approach, which incidentally would also be perfectly accurate, > is to store an alloc_percpu()-ed pointer at the call site, not the > counter itself. I don't think it could be done via the macro. If it were called during run time it would have to be special alloc_percpu() that didn't call back into the profiling code (which almost everything does do). > the current code needs more work before it can go upstream i think. It was never really planned to go upstream. It's ultimately a debugging feature that's really only needed in -mm .. Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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