Date: Mon, 18 Feb 2002 13:34:33 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Julian Elischer <julian@elischer.org> Cc: current@FreeBSD.ORG Subject: Re: Patch to improve mutex collision performance Message-ID: <200202182134.g1ILYXi42633@apollo.backplane.com> References: <Pine.BSF.4.21.0202181310500.52663-100000@InterJet.elischer.org>
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:> :> :can you detail in more clarity the flip-flopping you were seeing? :> :> Basically what is happening is that switch/wakeup overhead is being :> imposed unnecessarily. There is no need to switch if there is nothing :> to switch to, and this also causes the other process to not have to :> wakeup anyone when it releases Giant because process #1 is spinning :> on it instead of sleeping on it. So you immediate remove four context :> switches from the critical path. : :true, though the original code would halt the processor to reduce power :consumption on laptops etc. procrunnable doesn't include the idle :process. (a side-effect). That would still work, the spin only occurs when multiple cpus are vying for a sleep lock. But it's moot now, something isn't working as expected. It's as though procrunnable() is broken. -Matt Matthew Dillon <dillon@backplane.com> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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