Date: Tue, 31 Oct 2000 16:27:04 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: Bosko Milekic <bmilekic@dsuper.net> Cc: Terry Lambert <tlambert@primenet.com>, freebsd-arch@FreeBSD.ORG Subject: Re: MP: per-CPU mbuf allocation lists Message-ID: <20001031162704.H22110@fw.wintelcom.net> In-Reply-To: <Pine.BSF.4.21.0010311854240.37200-100000@jehovah.technokratis.com>; from bmilekic@dsuper.net on Tue, Oct 31, 2000 at 06:57:50PM -0500 References: <200010312344.QAA18978@usr09.primenet.com> <Pine.BSF.4.21.0010311854240.37200-100000@jehovah.technokratis.com>
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* Bosko Milekic <bmilekic@dsuper.net> [001031 15:53] wrote: > > On Tue, 31 Oct 2000, Terry Lambert wrote: > > > On the other hand, we know that significant concurrency can > > be achieved, even with a single Big Giant Lock, by removing > > resources from the conflict domain, rather than moving them > > to private conflict domains. Per CPU resources simply do not > > need locking or mutexes or atomic_t or similar protection: > > they are inherently MP-safe. > > Is this 100% accurate? Don't we still need to protect even the > per-CPU lists with a lock just in case we get an interrupt and get > rescheduled because of a higher priority thread that wants execution? Is > this possible? > If it isn't the case, then ignore the question, but if it is, I agree > that it still makes sense to have per-CPU resources available, just > because it the lock contention is minimized. The possiblity of using spinlocks which will turn off interrupts on the CPU that has aquired the spinlock may be used for leaf locks held for a very short time. But that's getting way ahead of ourselves. -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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