Date: Sun, 20 May 2012 22:22:18 +0200 (CEST) From: User Wojtek <wojtek@wojtek.tensor.gdynia.pl> To: Marko Zec <zec@fer.hr> Cc: alc@freebsd.org, freebsd-hackers@freebsd.org, freebsd-amd64@freebsd.org Subject: Re: superpages and kmem on amd64 Message-ID: <alpine.BSF.2.00.1205202219460.50838@wojtek.tensor.gdynia.pl> In-Reply-To: <201205201643.01194.zec@fer.hr> References: <201205200901.32613.zec@fer.hr> <CAJUyCcOWRKw5=NH_WrkKVcOMqGy2f3HroBX=pGbcbS3UbUZkxg@mail.gmail.com> <201205201643.01194.zec@fer.hr>
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>>> vm.pmap.pde.demotions: 31 >> >> No, your conclusion is incorrect. These counts show that 543 superpage >> mappings were created by promotion. > > OK, that sounds promising. Does "created by promotion" count reflect > historic / cumulative stats, or is vm.pmap.pde.promotions the actual number > of superpages active? Or should we subtract vm.pmap.pde.demotions from it to > get the current value? correction to my last answer. something is just wrong IMHO on my 2GB laptop: [root@wojtek ~]# sysctl -ad vm.pmap.pde vm.pmap.pde: 2MB page mapping counters vm.pmap.pde.promotions: 2MB page promotions vm.pmap.pde.p_failures: 2MB page promotion failures vm.pmap.pde.mappings: 2MB page mappings vm.pmap.pde.demotions: 2MB page demotions [root@wojtek ~]# sysctl -a vm.pmap.pde vm.pmap.pde.promotions: 61196 vm.pmap.pde.p_failures: 4796 vm.pmap.pde.mappings: 3051 vm.pmap.pde.demotions: 2306 from description seems like mappings could be current amount , but both it's value as well as promotions-demotions gives nonsense. with 2GB RAM there can not be 3051 or more 2MB pages mapped! and i - at present - doesn't run many large programs actually only some xterms and one compiling task.
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