Date: Tue, 11 Feb 2014 15:30:04 -0800 From: Adrian Chadd <adrian@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: FreeBSD Net <freebsd-net@freebsd.org>, Garrett Wollman <wollman@freebsd.org>, Navdeep Parhar <np@freebsd.org>, "net@freebsd.org" <net@freebsd.org> Subject: Re: Use of contiguous physical memory in cxgbe driver Message-ID: <CAJ-VmonCdNQPUCQwm0OhqQ3Kt_7x6-g-JwGVZQfzWTgrDYfmqw@mail.gmail.com> In-Reply-To: <201402111348.52135.jhb@freebsd.org> References: <21216.22944.314697.179039@hergotha.csail.mit.edu> <21216.36928.132606.318491@hergotha.csail.mit.edu> <CAJ-VmokL2nXX-cAOsXmW3YjiHmU86JfTco7P=Gcx2SFHNrGwSQ@mail.gmail.com> <201402111348.52135.jhb@freebsd.org>
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On 11 February 2014 10:48, John Baldwin <jhb@freebsd.org> wrote: > On Thursday, January 23, 2014 2:32:51 am Adrian Chadd wrote: >> It's about time we taught the physmem allocator to be more conducive >> to physically contiguous allocations. >> >> A server with gigabytes of memory should be able to keep a couple tens >> of megabytes of 64k sized allocation chunks around for exactly this. > > Alan Cox already taught the physmem allocator to do this for superpages. > However, this change was part of the superpages changes, so you can't count > experiences from machines older than about 7.2 when evaluating the > effectiveness of the new allocator. the problem is that we don't have pressure to _not_ fragment the physical memory from the allocator, so all of the memory ends up getting very fragmented versy quickly. the physmem superpage stuff stops being viable after a short while of say, "pound lots of packets around from vm objects" workload, because suddenly we end up chewing through all of physical memory with pages extremely quickly. -a
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