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Date: Fri, 29 Aug 2008 09:20:18 -0700 (PDT) From: Linus Torvalds <torvalds@...ux-foundation.org> To: Arjan van de Ven <arjan@...radead.org> cc: linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...x.de Subject: Re: [PATCH 4/5] select: make select() use schedule_hrtimeout() On Fri, 29 Aug 2008, Arjan van de Ven wrote: > > now that we have schedule_hrtimeout(), make select() use it. > But only for short delays; really long delays are assumed to not > need the highres level of accuracy but rather want the regular > timer behavior for now. This is _really_ ugly. Can't you just do this relaxation in "schedule_hrtimeout()" instead, and just document the fact that the "high resolution" of hrtimeout is relative to the length of the timeout. It's not that select() doesn't care, it's that *NOBODY* cares. If somebody asks for a timeout of one second and 2 microseconds, the two microseconds simply don't matter. Ever. But if somebody asks for a timeout of 12 microseconds, individual microseconds probably _do_ matter. So if you want high-resolution select/poll, then get rid of the "use_hr" logic entirely, and just do it unconditionally. Then, relax the scheduler timeouts in the scheduler. (But, that's probably _generally_ true. Even now, when people do "schedule_timeout()", there's a big difference between asking for two ticks and asking for two seconds. The latter should probably try to round to a nice timer tick basis for power reasons). Linus -- 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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