Date: Mon, 3 Mar 2008 21:37:07 -1000 (HST) From: Jeff Roberson <jroberson@chesapeake.net> To: David Xu <davidxu@FreeBSD.org> Cc: cvs-src@FreeBSD.org, Jeff Roberson <jeff@FreeBSD.org>, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern init_sysent.c syscalls.c systrace_args.c src/sys/sys syscall.h syscall.mk sysproto.h Message-ID: <20080303213630.D920@desktop> In-Reply-To: <47CCBD78.5040708@freebsd.org> References: <200803020741.m227fAoJ039644@repoman.freebsd.org> <47CB6FB0.9040602@freebsd.org> <20080302183513.P920@desktop> <47CCAF49.20903@freebsd.org> <20080303164227.S920@desktop> <47CCBD78.5040708@freebsd.org>
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On Tue, 4 Mar 2008, David Xu wrote: > Jeff Roberson wrote: >> >> On Tue, 4 Mar 2008, David Xu wrote: >> >>> Jeff Roberson wrote: >>> >>>>> One question is how I can determine the size of cpuset the kernel is >>>>> using ? >>>> >>>> I wrote it to tolerate user masks that were much larger than the kernel >>>> mask. I set the default CPU_SETSIZE in userspace to 128 and in kernel >>>> it's MAXCPU. So in practice an application shouldn't have to redefine >>>> CPU_SETSIZE. If your set is too small the kernel will return ERANGE >>>> however. Unfortunately, if your set is larger than the kernel's >>>> CPU_MAXSIZE it'll also return ERANGE. Maybe I should use different >>>> errnos for those cases. >>>> >>> >>> From my point, userland has to write some urgly code to guess what >>> kernel code wants, it is rather frustrate. >> >> You can use sysctl kern.smp.maxcpus to get the precise size. >> > > if kern.smp.maxcpus is a stable ABI, I may use it, can it be guaranteed? > I saw following code in kern_cpuset.c, obviously, maxcpus is not > respected. > > if (uap->cpusetsize < CPU_SETSIZE || uap->cpusetsize > CPU_MAXSIZE) > return (ERANGE); > > CPU_SETSIZE in the kernel is defined to MAXCPU. We can consider kern.smp.maxcpus a stable abi. I can make a note next to it and put it in the cpuset man page.
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