Re: [PATCH v2 0/2] powerpc: Add support for system call vectored

["Lucas A. M. Magalhaes" <lamm@linux.ibm.com>]

Hi Matheus,
Worked on top of Adhemerval's brk patch. But it fails if applied
directly on master.

Tested on a POWER9 with and without scv support.

Tested-by: Lucas A. M. Magalhães <lamm@linux.ibm.com>

Quoting Matheus Castanho via Libc-alpha (2020-12-03 14:15:26)
> This patchset enables the usage of system call vectored (scv) instruction by
> system calls for improved performance on POWER9 and later processors.
> 
> This new version dropped the patch to move brk to a C-based implementation, in
> favor of Adhemerval's patch [0]. So it should be applied on top of that.
> 
> Also, it modified the scv check mechanism to remove the thread pointer check as
> suggested by Florian. Now the dynamic loader always uses sc, static code still
> checks the thread pointer before accessing the TCB, and shared code (outside the
> dl) accesses the TCB directly.
> 
> Please check each patch for more details, specially 1/2 which explains the
> rationale and details of the runtime mechanism to choose between the old
> behavior (sc) and the new one (scv 0).
> 
> Tested on powerpc, powerpc64, and powerpc64le (with and without scv)
> 
> [0] https://sourceware.org/pipermail/libc-alpha/2020-November/119770.html
> 
> ---
> 
> v2:
>   - Fix typos and comments to match GNU style
>   - Remove the check for the thread pointer on shared code, and always use sc
>     when inside the dynamic loader
>   - Drop the patch implementing brk in C
> 
> Matheus Castanho (2):
>   powerpc: Runtime selection between sc and scv for syscalls
>   powerpc: Use scv instruction on clone when available
> 
>  sysdeps/powerpc/powerpc32/sysdep.h            |  15 ++-
>  sysdeps/powerpc/powerpc64/sysdep.h            | 120 +++++++++++++++++-
>  .../unix/sysv/linux/powerpc/powerpc64/clone.S |  36 +++++-
>  .../unix/sysv/linux/powerpc/powerpc64/vfork.S |   6 +-
>  sysdeps/unix/sysv/linux/powerpc/syscall.S     |  11 +-
>  sysdeps/unix/sysv/linux/powerpc/sysdep.h      |  93 ++++++++++----
>  6 files changed, 241 insertions(+), 40 deletions(-)
> 
> --
> 2.26.2