powerpc/64s: Avoid cpabort in context switch when possible

Browse source

The ISA v3.0B copy-paste facility only requires cpabort when switching
to a process that has foreign real addresses mapped (direct access to
accelerators), to clear a potential copy buffer filled by a previous
thread. There is no accelerator driver implemented yet, so cpabort can
be removed. It can be be re-added when a driver is implemented.

POWER9 DD1 requires the copy buffer to always be cleared on context
switch, but if accelerators are not in use, then an unpaired copy from
a dummy region is sufficient to clear data out of the copy buffer.

This increases context switch performance by about 5% on POWER9.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

...

This commit is contained in:

Nicholas Piggin 2017-06-09 01:36:09 +10:00 • committed by Michael Ellerman

parent 9145effd62

commit 07d2a628bc

3 changed files with 30 additions and 14 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

8

arch/powerpc/include/asm/ppc-opcode.h

View file

9

arch/powerpc/kernel/entry_64.S

View file

27

arch/powerpc/kernel/process.c

View file