Date: Mon, 1 Jun 2015 11:54:11 +0200 From: Marko Zec <zec@fer.hr> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: FreeBSD Current <current@freebsd.org> Subject: Re: superpages in FreeBSD (netmap related) ? Message-ID: <20150601115411.1f95bd00@x23> In-Reply-To: <CA%2BhQ2%2Bh7LZp2cLUpOrqLvWwFmSSWSw4GKT1DJCc_AuH7-t042g@mail.gmail.com> References: <CA%2BhQ2%2BiWq4rO-V0M9VZTHMcVORSJ_Qgn6u0JmSiZjTy-L2MAsQ@mail.gmail.com> <CA%2BhQ2%2Bh7LZp2cLUpOrqLvWwFmSSWSw4GKT1DJCc_AuH7-t042g@mail.gmail.com>
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On Mon, 1 Jun 2015 11:34:00 +0200 Luigi Rizzo <rizzo@iet.unipi.it> 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 */ OTOH I'm not aware of any mechanisms for forcing superpage allocations at malloc() time. Marko
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