Date: Wed, 27 Oct 2010 12:18:38 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: David Xu <davidxu@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Garrett Cooper <gcooper@freebsd.org> Subject: Re: svn commit: r214409 - head/sys/kern Message-ID: <alpine.BSF.2.00.1010271216160.32645@fledge.watson.org> In-Reply-To: <4CC80ABA.3080404@freebsd.org> References: <201010270232.o9R2Wsu3084553@svn.freebsd.org> <AANLkTi=2dTVmB8Goj%2BNXq4F6SmZBNS3bxn8gLjmQ%2BdfV@mail.gmail.com> <4CC803A8.3040602@freebsd.org> <AANLkTimddEnxCLNWd%2BtWVANXCzu8ZkNHQumXCU8a_8yT@mail.gmail.com> <4CC80ABA.3080404@freebsd.org>
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On Wed, 27 Oct 2010, David Xu wrote: >>> I really hate to see such a problem that userland can not figure out what >>> kernel is using, I try hardly to guess, but still can not find what it is >>> using. yes, I think the doc may need to be fixed or another syscall is >>> needed. >> >> Well... Jeff's code in cpuset(1) does some trivial sizeof(mask) 's, but >> it just passes in cpuset_t for mask. I've seen different calling >> conventions at the kernel level when I tried to get my brain in sync with >> that for a bug I was looking at a few weeks ago (and sadly, failed to some >> degree). >> These syscalls are a bit confusing though, and apart from cpuset(1) >> there aren't any really good examples in the sourcebase on how to use them >> (at least not the last time I checked)... Thanks, -Garrett >> > The problem is that the size of cpuset is not fixed, it is tunable by the > recompiling kernel with different parameter, so if you have a program which > you want to adapt it to use any size of cpuset, it should be able to get the > size the kernel is using, if you don't have source code of the program, you > can not compile it with new parameter, then there is trouble. Yay, it's fd_set all over again :-). It sounds like we might just need to add a sysctl and a few wrapper functions in userspace along the lines of (hand-wave): cpuset_t *cpuset_alloc(); void cpuset_free(); And perhaps some sort of API that abstracts manipulation of the set (or doesn't but allows the user to easily query its bounds). Robert
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