Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT

From	Vlastimil Babka <vbabka@suse.cz>
Newsgroups	linux.kernel
Subject	Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT
Date	2015-08-24 15:40 +0200
Message-ID	<q108G-Hc-23@gated-at.bofh.it> (permalink)
References	(4 earlier) <pZsVr-70t-5@gated-at.bofh.it> <pZBvJ-2L0-23@gated-at.bofh.it> <pZOVZ-5dT-21@gated-at.bofh.it> <pZZom-3ny-5@gated-at.bofh.it> <q0X18-4Km-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

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)?
--
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/

Thread

Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-19 23:40 +0200
  Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Michal Hocko <mhocko@kernel.org> - 2015-08-20 10:00 +0200
    Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-20 19:10 +0200
      Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Michal Hocko <mhocko@kernel.org> - 2015-08-21 09:30 +0200
        Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-21 20:40 +0200
          Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Konstantin Khlebnikov <koct9i@gmail.com> - 2015-08-24 12:20 +0200
            Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Vlastimil Babka <vbabka@suse.cz> - 2015-08-24 15:40 +0200
              Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Konstantin Khlebnikov <koct9i@gmail.com> - 2015-08-24 16:00 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Vlastimil Babka <vbabka@suse.cz> - 2015-08-24 16:30 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-24 17:10 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Konstantin Khlebnikov <koct9i@gmail.com> - 2015-08-24 17:50 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-24 18:00 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Konstantin Khlebnikov <koct9i@gmail.com> - 2015-08-24 18:30 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-24 19:10 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Konstantin Khlebnikov <koct9i@gmail.com> - 2015-08-24 21:00 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-24 22:30 +0200
          Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Michal Hocko <mhocko@kernel.org> - 2015-08-25 15:50 +0200
            Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Vlastimil Babka <vbabka@suse.cz> - 2015-08-25 16:00 +0200
              Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Michal Hocko <mhocko@kernel.org> - 2015-08-25 16:30 +0200
            Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Konstantin Khlebnikov <koct9i@gmail.com> - 2015-08-25 16:00 +0200
            Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-25 16:30 +0200
              Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Michal Hocko <mhocko@kernel.org> - 2015-08-25 21:00 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Eric B Munson <emunson@akamai.com> - 2015-08-25 21:10 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Michal Hocko <mhocko@kernel.org> - 2015-08-26 09:30 +0200
                Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Vlastimil Babka <vbabka@suse.cz> - 2015-08-26 17:40 +0200
  Re: [PATCH v7 3/6] mm: Introduce VM_LOCKONFAULT Vlastimil Babka <vbabka@suse.cz> - 2015-08-20 10:00 +0200

csiph-web