Date: Sun, 28 Nov 1999 16:38:38 -0600 From: "Richard Seaman, Jr." <dick@tar.com> To: Julian Elischer <julian@whistle.com> Cc: "Richard Seaman, Jr." <dick@tar.com>, arch@freebsd.org Subject: Re: syscall overhead. Message-ID: <19991128163838.A29767@tar.com> In-Reply-To: <Pine.BSF.4.10.9911281428460.544-100000@current1.whistle.com> References: <19991128111949.O1408@tar.com> <Pine.BSF.4.10.9911281428460.544-100000@current1.whistle.com>
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On Sun, Nov 28, 1999 at 02:32:50PM -0800, Julian Elischer wrote: > > I don't have any threaded apps that come close to this, but perhaps > > they exist. And, unless you can fix the "user thread" scheduler so > > it doesn't make any syscalls, its hard to see much of an advantage > > for user thread context switches over kernel thread context switches, > > from a performance standpoint. (The current user thread scheduler > > can actually be slower at context switches that kernel threads, > > because of the nubmer of syscalls it makes). > > > > yes but have we catalogued those calls? Not me, but it's not hard. > I am guessing that we can probably get rid of a lot of them by appropriate > kernel support. For sure. Its interesting, but I think good "user threads" needs a lot more kernel support than pure "kernel threads". The real question, which might really make a difference, is can you get rid of *all* syscalls for at least some subset of the UTS context switches. I don't think you can get rid of at least one syscall in at least some cases. > For example threads blocking and unblocking signals for various reasons.. > I'm certain we could do the same lazy blocking that the kernel > presently does So that blocking a signal would be simply a case of > setting a bit. Or, as another example, is there a way to implement shared scheduling information between the kernel and the UTS without a syscall for every bit of shared information. -- Richard Seaman, Jr. email: dick@tar.com 5182 N. Maple Lane phone: 262-367-5450 Chenequa WI 53058 fax: 262-367-5852 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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