Re: [[RFC][PATCH] v1 0/2] malloc/realloc with transparent huge page support

["H.J. Lu" <hjl.tools@gmail.com>]

On Sun, May 3, 2020 at 3:09 PM Norbert Manthey
<nmanthey@conp-solutions.com> wrote:
>
> Dear all,
>
> I have been looking for a way to enable huge pages in a user land process
> without privileges, and without modifying the source of the process.
>
> Huge pages had to be used explicitly via linking against special libraries.
> An alternative are transparent huge pages, which are easier to obtain, but there
> are no guarantees of success. Using transparent huge pages can also result in
> slowdowns. Many Linux based distributions enable transparent huge pages via
> madvise, so that user land processes. With the madvise system call, a process
> can control whether allocated memory should be mapped with huge pages. However,
> the process typically only sees the allocations returned via a single malloc or
> realloc invocation, most of them being rather small.
>
> For a larger impact, I modified the way allocations are done behind the scenes.
> For the allocated memory, I changed the properties to (1) align to 2M instead
> of 4K, and (2) to call the madvise system call after the brk system call, to
> signal that the used memory area should be mapped with huge pages.
>
> The default behavior is not modified. The modification can currently be enabled,
> by specifying the environment variable GLIBC_THP_ALWAYS.
>

Please use GLIBC_TUNABLES framework.

-- 
H.J.