lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Thu, 25 Jan 2024 21:03:12 +0800
From: Lance Yang <ioworker0@...il.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org
Subject: Re: [Issue] mprotect+madvise may be better than mmap for permission
 changes and page zeroing

Thanks!

On Thu, Jan 25, 2024 at 8:44 PM David Hildenbrand <david@...hat.com> wrote:
>
> On 25.01.24 13:28, Lance Yang wrote:
> > Hello Everyone,
> >
> > I've noticed that using mprotect(PROT_NONE) with
> > madvise(MADV_DONTNEED) is much faster than
> > mmap(PROT_NONE, MAP_FIXED) alone for changing
> > permissions and zeroing pages.
> >
> > I have maintained a chunk-allocator internally at the
> > company. It allocates a chunk using
> > mmap(PROT_READ|PROT_WRITE, MAP_ANON|MAP_PRIVATE, -1, 0),
> > releases a chunk using mmap(PROT_NONE, MAP_ANON|MAP_FIXED|MAP_PRIVATE, -1, 0),
> > and reuses a chunk using mprotect(PROT_READ|PROT_WRITE).
> > Recently, I replaced mmap(PROT_NONE, MAP_FIXED) with
> > mprotect(PROT_NONE) + madvise(MADV_DONTNEED) to
> > reduce the latency of releasing chunks.
> >
> > Test code:
> > https://github.com/ioworker0/mmapvsmprotect/blob/main/test2.c
> >
> > Here are the test results on my machine:
> > CPU: AMD EPYC 7R13 Processor
> > Kernel: 6.2.0
> > Elapsed Time for mprotect+madvise: 3670 nanoseconds
> > Elapsed Time for mmap: 5520 nanoseconds
>
> mprotect+madvise won't free page tables, mmap will. That's the biggest
> difference.
>
> --
> Cheers,
>
> David / dhildenb
>

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ