lkml.org 
[lkml]   [2015]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT
From
Date
On 08/24/2015 12:17 PM, Konstantin Khlebnikov wrote:
>>
>> I am in the middle of implementing lock on fault this way, but I cannot
>> see how we will hanlde mremap of a lock on fault region. Say we have
>> the following:
>>
>> addr = mmap(len, MAP_ANONYMOUS, ...);
>> mlock(addr, len, MLOCK_ONFAULT);
>> ...
>> mremap(addr, len, 2 * len, ...)
>>
>> There is no way for mremap to know that the area being remapped was lock
>> on fault so it will be locked and prefaulted by remap. How can we avoid
>> this without tracking per vma if it was locked with lock or lock on
>> fault?
>
> remap can count filled ptes and prefault only completely populated areas.

Does (and should) mremap really prefault non-present pages? Shouldn't it
just prepare the page tables and that's it?

> There might be a problem after failed populate: remap will handle them
> as lock on fault. In this case we can fill ptes with swap-like non-present
> entries to remember that fact and count them as should-be-locked pages.

I don't think we should strive to have mremap try to fix the inherent
unreliability of mmap (MAP_POPULATE)?


\
 
 \ /
  Last update: 2015-08-24 15:41    [W:0.131 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site