Date: Mon, 9 Aug 2010 14:05:05 +0200 From: Attilio Rao <attilio@freebsd.org> To: "Jayachandran C." <c.jayachandran@gmail.com> Cc: src-committers@freebsd.org, John Baldwin <jhb@freebsd.org>, "Jayachandran C." <jchandra@freebsd.org>, svn-src-all@freebsd.org, Joe Landers <jlanders@vmware.com>, Randall Stewart <rrs@freebsd.org>, sbruno@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r208165 - in head/sys: kern mips/conf mips/include mips/mips mips/rmi mips/rmi/dev/xlr Message-ID: <AANLkTim_pTQgquRRuz4G=jC5G0Amc%2ByF6VeDcg-cpTCX@mail.gmail.com> In-Reply-To: <AANLkTi=jkUiXStPV3Gq206GgmctM9%2B1ofbNWuh5CSeWw@mail.gmail.com> References: <201005161943.o4GJhnTo096839@svn.freebsd.org> <AANLkTikAarFgbxgGu-8XG7gh6VidPoVGwva54NN4rcRF@mail.gmail.com> <AANLkTi=jkUiXStPV3Gq206GgmctM9%2B1ofbNWuh5CSeWw@mail.gmail.com>
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2010/8/9 Jayachandran C. <c.jayachandran@gmail.com>: > On Mon, Aug 9, 2010 at 5:31 AM, Attilio Rao <attilio@freebsd.org> wrote: >> 2010/5/16 Randall Stewart <rrs@freebsd.org>: >>> Author: rrs >>> Date: Sun May 16 19:43:48 2010 >>> New Revision: 208165 >>> URL: http://svn.freebsd.org/changeset/base/208165 >>> >>> Log: >>> This pushes all of JC's patches that I have in place. I >>> am now able to run 32 cores ok.. but I still will hang >>> on buildworld with a NFS problem. I suspect I am missing >>> a patch for the netlogic rge driver. >>> >>> JC check and see if I am missing anything except your >>> core-mask changes >> >> >>> Modified: head/sys/kern/subr_smp.c >>> ============================================================================== >>> --- head/sys/kern/subr_smp.c Sun May 16 19:25:56 2010 (r208164) >>> +++ head/sys/kern/subr_smp.c Sun May 16 19:43:48 2010 (r208165) >>> @@ -503,7 +503,10 @@ smp_topo_none(void) >>> top = &group[0]; >>> top->cg_parent = NULL; >>> top->cg_child = NULL; >>> - top->cg_mask = (1 << mp_ncpus) - 1; >>> + if (mp_ncpus == sizeof(top->cg_mask) * 8) >>> + top->cg_mask = -1; >>> + else >>> + top->cg_mask = (1 << mp_ncpus) - 1; >>> top->cg_count = mp_ncpus; >>> top->cg_children = 0; >>> top->cg_level = CG_SHARE_NONE; >>> >> >> ... and this is why I particulary hate big commits with complete lack >> of technical details. >> >> This particulary chunk was supposed to fix a nasty and completely MI >> bug that some users have already met (kern/148698). The complete lack >> of details didn't help in identify the issue neither that it was a >> valuable fix. >> >> The fix is, however, improper (there is no clear relationship between >> the multiplication and why that happens) thus I would rather use what >> Joe has reported in the PR. > > > I was not aware of the PR when I sent this changes to rrs@, and this > went as a part of MIPS SMP support for XLR which has 32 CPUs > > But I'm not sure that the current change is correct, cg_mask is of > type cpumask_t and I don't think it is guaranteed to be 32 bit (as it > is a machine dependent type). Actually the 32 bits limit is well aware and acknowledged in cpumask_t. While it is true that it should be an 'opaque' type, in reality it is not. The maximum limit of 32 CPUs is a reality due to cpumask_t on all our architectures. That is why we are going to use cpuset_t for dealing with CPUs numbers (which is really opaque, at same extent, and is not bound to any size). Attilio -- Peace can only be achieved by understanding - A. Einstein
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