Messages in this thread | | | From | Alexei Fedotov <> | Date | Wed, 16 Jul 2014 10:23:22 +0400 | Subject | Re: Where in the code mmap + MAP_ANONYMOUS clears returned pages? |
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Thanks, Michal! -- With best regards / с наилучшими пожеланиями, Alexei Fedotov / Алексей Федотов, http://dataved.ru/ +7 916 562 8095
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On Tue, Jul 15, 2014 at 11:14 PM, Michal Hocko <mhocko@suse.cz> wrote: > On Tue 15-07-14 21:55:03, Alexei Fedotov wrote: >> Guys, >> >> I look into mmap.c code [1] and try to understand where anonymous >> memory mapping (mmap + MAP_ANONYMOUS) sets memory to zero. My best >> guess is I should dig that somewhere in mmap_region. >> >> Could you please help me locating the code which makes returned memory >> pages clean? Thank you in advance. > > mmap doesn't allocate pages which back the mapping directly unless it is > told to by MAP_POPULATE. So the clean pages are either allocated during > the page fault path when the memory is accessed (see do_anonymous_page > for private 4k pages fault, do_huge_pmd_anonymous_page for THP page and > MAP_SHARED is left as an excercise for the reader ;)) or in mmap path > directly when MAP_POPULATE is specified (see vm_mmap_pgoff which calls > mm_populate) > >> >> [1] http://code.ohloh.net/file?fid=RPa2fuiQ5j_IwR1nymptYBBC3X4&cid=w6qrXNDsMqk >> >> -- >> With best regards / с наилучшими пожеланиями, >> Alexei Fedotov / Алексей Федотов, >> http://dataved.ru/ >> +7 916 562 8095 >> >> [1] Start using Apache Openmeetings today, http://openmeetings.apache.org/ >> [2] Join Alexei Fedotov @linkedin, http://ru.linkedin.com/in/dataved/ >> [3] Join Alexei Fedotov @facebook, http://www.facebook.com/openmeetings >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ > > -- > Michal Hocko > SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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