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Date: Wed, 27 Sep 2017 13:51:09 +0800 From: Xishi Qiu <qiuxishi@...wei.com> To: Michal Hocko <mhocko@...nel.org> CC: Vlastimil Babka <vbabka@...e.cz>, Joonsoo Kim <iamjoonsoo.kim@....com>, Mel Gorman <mgorman@...hsingularity.net>, Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, zhong jiang <zhongjiang@...wei.com>, yeyunfeng <yeyunfeng@...wei.com>, <wanghaitao12@...wei.com>, "Zhoukang (A)" <zhoukang7@...wei.com> Subject: Re: [RFC] a question about mlockall() and mprotect() On 2017/9/26 19:00, Michal Hocko wrote: > On Tue 26-09-17 11:45:16, Vlastimil Babka wrote: >> On 09/26/2017 11:22 AM, Xishi Qiu wrote: >>> On 2017/9/26 17:13, Xishi Qiu wrote: >>>>> This is still very fuzzy. What are you actually trying to achieve? >>>> >>>> I don't expect page fault any more after mlock. >>>> >>> >>> Our apps is some thing like RT, and page-fault maybe cause a lot of time, >>> e.g. lock, mem reclaim ..., so I use mlock and don't want page fault >>> any more. >> >> Why does your app then have restricted mprotect when calling mlockall() >> and only later adjusts the mprotect? > > Ahh, OK I see what is goging on. So you have PROT_NONE vma at the time > mlockall and then later mprotect it something else and want to fault all > that memory at the mprotect time? > > So basically to do > --- > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 6d3e2f082290..b665b5d1c544 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -369,7 +369,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev, > * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major > * fault on access. > */ > - if ((oldflags & (VM_WRITE | VM_SHARED | VM_LOCKED)) == VM_LOCKED && > + if ((oldflags & (VM_WRITE | VM_LOCKED)) == VM_LOCKED && > (newflags & VM_WRITE)) { > populate_vma_page_range(vma, start, end, NULL); > } > Hi Michal, My kernel is v3.10, and I missed this code, thank you reminding me. Thanks, Xishi Qiu
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