Date: Thu, 25 Oct 2012 09:50:57 -0400 From: John Baldwin <jhb@freebsd.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, Alfred Perlstein <alfred@freebsd.org>, src-committers@freebsd.org Subject: Re: svn commit: r242029 - head/sys/kern Message-ID: <201210250950.57161.jhb@freebsd.org> In-Reply-To: <20121025080551.GG35915@deviant.kiev.zoral.com.ua> References: <201210250146.q9P1kLi8043704@svn.freebsd.org> <20121025080551.GG35915@deviant.kiev.zoral.com.ua>
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On Thursday, October 25, 2012 4:05:51 am Konstantin Belousov wrote: > On Thu, Oct 25, 2012 at 01:46:21AM +0000, Alfred Perlstein wrote: > > Author: alfred > > Date: Thu Oct 25 01:46:20 2012 > > New Revision: 242029 > > URL: http://svn.freebsd.org/changeset/base/242029 > > > > Log: > > Allow autotune maxusers > 384 on 64 bit machines > > > > A default install on large memory machines with multiple 10gigE interfaces > > were not being given enough mbufs to do full bandwidth TCP or NFS traffic. > > > > To keep the value somewhat reasonable, we scale back the number of > > maxuers by 1/6 past the 384 point. This gives us enough mbufs for most > > of our pretty basic 10gigE line-speed tests to complete. > > > > Modified: > > head/sys/kern/subr_param.c > > > > Modified: head/sys/kern/subr_param.c > > ============================================================================== > > --- head/sys/kern/subr_param.c Thu Oct 25 01:27:01 2012 (r242028) > > +++ head/sys/kern/subr_param.c Thu Oct 25 01:46:20 2012 (r242029) > > @@ -278,8 +278,16 @@ init_param2(long physpages) > > maxusers = physpages / (2 * 1024 * 1024 / PAGE_SIZE); > > if (maxusers < 32) > > maxusers = 32; > > - if (maxusers > 384) > > - maxusers = 384; > > + /* > > + * Clips maxusers to 384 on machines with <= 4GB RAM or 32bit. > > + * Scales it down 6x for large memory machines. > > + */ > > + if (maxusers > 384) { > > + if (sizeof(void *) <= 4) > > + maxusers = 384; > > + else > > + maxusers = 384 + ((maxusers - 384) / 6); > > + } > This is unbelievably weird way to express the '64bit'. The > #ifdef _LP64 is enough there instead of the runtime check. > > Also, are you sure that all our 64bit arches do not have KVA limitations ? There is an active thread on current@ with a different patch that uses a KVA constant to derive 384 instead. When we have updated tuning in the past (e.g. adjusting the cap on maxvnodes), there was a bit of discussion rather than a random drive by commit. I think we should probably hold off on making changes here and figure out what the right way to fix this is in the thread on current@ instead. Andre has already suggested divorcing mbuf tuning from maxusers entirely for example. -- John Baldwin
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