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Date:   Thu, 18 Feb 2021 12:07:26 +0100
From:   Rolf Eike Beer <eike-kernel@sf-tec.de>
To:     Vlastimil Babka <vbabka@suse.cz>
Cc:     David Hildenbrand <david@redhat.com>, linux-kernel@vger.kernel.org,
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        Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH RFC] mm/madvise: introduce MADV_POPULATE to
 prefault/prealloc memory
In-Reply-To: <7859a7a0-96e2-72ff-be92-c0af5d642564@suse.cz>
References: <20210217154844.12392-1-david@redhat.com>
 <7859a7a0-96e2-72ff-be92-c0af5d642564@suse.cz>
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>> 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