Re: Direct io on block device has performance regression on 2.6.x kernel

From: Jesse Barnes
Date: Wed Mar 09 2005 - 23:40:20 EST

On Wednesday, March 9, 2005 3:23 pm, Andi Kleen wrote:
> "Chen, Kenneth W" <kenneth.w.chen@xxxxxxxxx> writes:
> > Just to clarify here, these data need to be taken at grain of salt. A
> > high count in _spin_unlock_* functions do not automatically points to
> > lock contention. It's one of the blind spot syndrome with timer based
> > profile on ia64. There are some lock contentions in 2.6 kernel that
> > we are staring at. Please do not misinterpret the number here.
> Why don't you use oprofileÂ>? It uses NMIs and can profile "inside"
> interrupt disabled sections.

Oh, and there are other ways of doing interrupt off profiling by using the
PMU. q-tools can do this I think.

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