Date: Thu, 1 Sep 2011 19:22:47 +0200 From: Attilio Rao <attilio@freebsd.org> To: Ivan Voras <ivoras@freebsd.org> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, Sean Bruno <seanbru@yahoo-inc.com> Subject: Re: Large machine test ideas Message-ID: <CAJ-FndDsZ86ra_GaWqGoQ8QLD=AFuaaFWhedGnSGEcAAtbKFLQ@mail.gmail.com> In-Reply-To: <CAF-QHFUCYJL28GxQu_=QjGgiBOVumNK56tO2rnmmTo4%2B%2Bjf0yw@mail.gmail.com> References: <j38lj5$s9a$1@dough.gmane.org> <CAMBSHm_Sv_KZUs4h-tDGAZCq8s2qo_bMmfZxLbVkcH1=_Wu0OQ@mail.gmail.com> <CAF-QHFW=aU3=iKE9WMg6%2BD6eP9OXth=c0AidBc140ykmAPD2zg@mail.gmail.com> <201108291415.32605.jhb@freebsd.org> <j3ju8s$kuo$2@dough.gmane.org> <1314818323.2610.6.camel@hitfishpass-lx.corp.yahoo.com> <CAJ-FndCbXs0btQUc8_L3F4kcsdu5WN-75HY%2BhdKY%2B5OGhase2Q@mail.gmail.com> <CAF-QHFUCYJL28GxQu_=QjGgiBOVumNK56tO2rnmmTo4%2B%2Bjf0yw@mail.gmail.com>
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2011/9/1 Ivan Voras <ivoras@freebsd.org>: > On 1 September 2011 16:11, Attilio Rao <attilio@freebsd.org> wrote: > >>> I mean, if we have 2 cpus in a machine, but MAXCPU is set to 256, there >>> is a bunch of "lost" memory and higher levels of lock contention? >>> >>> I thought that attilio was taking a stab at enhancing this, but at the >>> current time anything more than a value of 64 for MAXCPU is kind of a >>> "caveat emptor" area of FreeBSD. >> >> With newest current you can redefine MAXCPU in your kernel config, so >> you don't need to bump the default value. >> I think 64 as default value is good enough. >> >> Removing MAXCPU dependency from the KBI is an important project >> someone should adopt and bring to conclusion. > > That's certainly one half of it and thanks for the work, but the real > question in this thread is what Sean asked: what are the negative > side-effects of simply bumping MAXCPU to 256 by default? AFAIK, there > are not that many structures which are statically sized by MAXCMPU and > most use the runtime-detected smp_cpus? > Well, there are quite a few statically allocated, but as I said, making the kernel MAXCPU-agnostic (or sort of agnostic) is a goal and a good project. Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein
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