Messages in this thread | | | Subject | Re: [PATCH 1/2] x86-64 TIF flags for debug regs and io bitmap in ctxsw | From | Arjan van de Ven <> | Date | Tue, 04 Jul 2006 10:22:16 +0200 |
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On Tue, 2006-07-04 at 10:09 +0200, Andi Kleen wrote: > On Tuesday 04 July 2006 09:51, Arjan van de Ven wrote: > > > - } > > > - } > > > + if (unlikely((task_thread_info(next_p)->flags & _TIF_WORK_CTXSW)) > > > + || test_tsk_thread_flag(prev_p, TIF_IO_BITMAP)) > > > + __switch_to_xtra(prev_p, next_p, tss); > > > > well isn't this replacing an if() (which isn't cheap but also not > > expensive, due to unlikely()) with an atomic operation (which *is* > > expensive) ? > > Where do you see an atomic operation?
test_tsk_thread_flag() ends up doing an atomic op afaics
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