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Date: Tue, 20 Jan 2015 10:08:16 +0100 From: Vlastimil Babka <vbabka@...e.cz> To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, Andrew Morton <akpm@...ux-foundation.org> CC: "Kirill A. Shutemov" <kirill@...temov.name>, David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH V3] mm/thp: Allocate transparent hugepages on local node On 01/20/2015 06:52 AM, Aneesh Kumar K.V wrote: > Vlastimil Babka <vbabka@...e.cz> writes: > >> On 01/17/2015 01:02 AM, Andrew Morton wrote: >>> On Fri, 16 Jan 2015 12:56:36 +0530 "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> wrote: >>> >>>> This make sure that we try to allocate hugepages from local node if >>>> allowed by mempolicy. If we can't, we fallback to small page allocation >>>> based on mempolicy. This is based on the observation that allocating pages >>>> on local node is more beneficial than allocating hugepages on remote node. >>> >>> The changelog is a bit incomplete. It doesn't describe the current >>> behaviour, nor what is wrong with it. What are the before-and-after >>> effects of this change? >>> >>> And what might be the user-visible effects? >>> >>>> --- a/mm/mempolicy.c >>>> +++ b/mm/mempolicy.c >>>> @@ -2030,6 +2030,46 @@ retry_cpuset: >>>> return page; >>>> } >>>> >>>> +struct page *alloc_hugepage_vma(gfp_t gfp, struct vm_area_struct *vma, >>>> + unsigned long addr, int order) >>> >>> alloc_pages_vma() is nicely documented. alloc_hugepage_vma() is not >>> documented at all. This makes it a bit had for readers to work out the >>> difference! >>> >>> Is it possible to scrunch them both into the same function? Probably >>> too messy? >> >> Hm that could work, alloc_pages_vma already has an if (MPOL_INTERLEAVE) part, so >> just put the THP specialities into an "else if (huge_page)" part there? >> >> You could probably test for GFP_TRANSHUGE the same way as __alloc_pages_slowpath >> does. There might be false positives theoretically, but is there anything else >> that would use these flags and not be a THP? >> > > is that check correct ? ie, > > if ((gfp & GFP_TRANSHUGE) == GFP_TRANSHUGE) > > may not always indicate transparent hugepage if defrag = 0 . With defrag > cleared, we remove __GFP_WAIT from GFP_TRANSHUGE. Yep, that looks wrong. Sigh. I guess we can't spare an extra GFP flag to indicate TRANSHUGE? > static inline gfp_t alloc_hugepage_gfpmask(int defrag, gfp_t extra_gfp) > { > return (GFP_TRANSHUGE & ~(defrag ? 0 : __GFP_WAIT)) | extra_gfp; > } > > -aneesh > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@...ck.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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