linux-kernel - Re: [PATCH RFC] mm/madvise: introduce MADV

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Message-ID: <50f73055950ff7382f2194134ef0f439@sf-tec.de>
Date:   Thu, 18 Feb 2021 12:07:26 +0100
From:   Rolf Eike Beer <eike-kernel@...tec.de>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        Matthew Wilcox <willy@...radead.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Minchan Kim <minchan@...nel.org>, Jann Horn <jannh@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dave Hansen <dave.hansen@...el.com>,
        Hugh Dickins <hughd@...gle.com>,
        Rik van Riel <riel@...riel.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>, linux-alpha@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, linux-arch@...r.kernel.org,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to
 prefault/prealloc memory

>> Let's introduce MADV_POPULATE with the following semantics
>> 1. MADV_POPULATED does not work on PROT_NONE and special VMAs. It 
>> works
>>    on everything else.
>> 2. Errors during MADV_POPULATED (especially OOM) are reported. If we 
>> hit
>>    hardware errors on pages, ignore them - nothing we really can or
>>    should do.
>> 3. On errors during MADV_POPULATED, some memory might have been
>>    populated. Callers have to clean up if they care.
>> 4. Concurrent changes to the virtual memory layour are tolerated - we
                                                     ^t
>>    process each and every PFN only once, though.
>> 5. If MADV_POPULATE succeeds, all memory in the range can be accessed
>>    without SIGBUS. (of course, not if user space changed mappings in 
>> the
>>    meantime or KSM kicked in on anonymous memory).

You are talking both about MADV_POPULATE and MADV_POPULATED here.

Eike