Date: Mon, 1 Jun 2015 12:11:12 +0200 From: Luigi Rizzo <rizzo@iet.unipi.it> To: Marko Zec <zec@fer.hr> Cc: FreeBSD Current <current@freebsd.org>, Giuseppe Lettieri <g.lettieri@iet.unipi.it>, Stefano Garzarella <stefanogarzarella@gmail.com>, Vincenzo Maffione <v.maffione@gmail.com>, Luigi Rizzo <rizzo@iet.unipi.it> Subject: Re: superpages in FreeBSD (netmap related) ? Message-ID: <CA%2BhQ2%2BhkWth=obecWzuXdfESeRXhGdzng7_Mj0g3HkMo=oyWNQ@mail.gmail.com> In-Reply-To: <20150601115411.1f95bd00@x23> References: <CA%2BhQ2%2BiWq4rO-V0M9VZTHMcVORSJ_Qgn6u0JmSiZjTy-L2MAsQ@mail.gmail.com> <CA%2BhQ2%2Bh7LZp2cLUpOrqLvWwFmSSWSw4GKT1DJCc_AuH7-t042g@mail.gmail.com> <20150601115411.1f95bd00@x23>
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On Monday, June 1, 2015, Marko Zec <zec@fer.hr> wrote: > On Mon, 1 Jun 2015 11:34:00 +0200 > Luigi Rizzo <rizzo@iet.unipi.it <javascript:;>> wrote: > > > Hi, > > i was wondering how we can improve the netmap memory allocator > > to make use of 2M pages (through the page promotion trick). > > > > in netmap, when we allocate packet buffers, > > we issue requests for 4k blocks to contigmalloc(), > > and i have no idea if there is a way to improve the > > chance that the memory is mapped to 2M pages ? > > In my (previous life) experience, when requested large enough blocks, > malloc() did a good job at automatically promoting those to superpages, > and in my applications this behavior was 100% consistent, at least on > amd64. After the block is allocated one can check whether it is > superpage-mapped: > > pmap_t pmap = vmspace_pmap(curthread->td_proc->p_vmspace); > > if (pmap_mincore(pmap, (vm_offset_t) addr) & MINCORE_SUPER) > /* you're good */ > else > /* bad luck */ Thanks. Do you know if there is any way to run some equivalente test from user space ? Cheers Luigi > OTOH I'm not aware of any mechanisms for forcing superpage allocations > at malloc() time. > > Marko > -- -----------------------------------------+------------------------------- Prof. Luigi RIZZO, rizzo@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL +39-050-2217533 . via Diotisalvi 2 Mobile +39-338-6809875 . 56122 PISA (Italy) -----------------------------------------+-------------------------------
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