Date: Fri, 01 Feb 2013 20:58:50 +0100 From: Andre Oppermann <andre@freebsd.org> To: Alan Cox <alc@rice.edu> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r246204 - head/sys/arm/include Message-ID: <510C1E7A.2090509@freebsd.org> In-Reply-To: <510C00CB.8000409@rice.edu> References: <201302011026.r11AQVL9068427@svn.freebsd.org> <510C00CB.8000409@rice.edu>
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On 01.02.2013 18:52, Alan Cox wrote: > On 02/01/2013 04:26, Andre Oppermann wrote: >> Author: andre >> Date: Fri Feb 1 10:26:31 2013 >> New Revision: 246204 >> URL: http://svnweb.freebsd.org/changeset/base/246204 >> >> Log: >> Add VM_KMEM_SIZE_SCALE parameter set to 2 (50%) for all ARM platforms. >> >> VM_KMEM_SIZE_SCALE specifies which fraction of the available physical >> memory, after deduction of the kernel itself and other early statically >> allocated memory, can be used for the kmem_map. The kmem_map provides >> for all UMA/malloc allocations in KVM space. >> > > Not always. Off the top of my head, two things immediately come to > mind: 9KB and 16KB jumbo frames come from the kernel map, because we > allocate physically contiguous memory for them, and some swap metadata > also comes from the kernel map. I'd love to remove jumbo clusters that are larger than PAGE_SIZE. The hard need of s/g challenged network cards is gone. All contemporary networks can deliver a jumbo frame into a PAGE_SIZE'd mbuf cluster chains. Some can even split off the headers into a separate mbuf. A quick search for kernel_map allocations didn't show many other direct users of the kernel_map. The XEN net and blk backends do make use of it. Other users have their own submaps: exec_map, pipe_map, buffer_map and pager_map. > Yes, all "ordinary" heap allocations come from the kmem map, but a > number of things that are special for one reason or another don't. -- Andre
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