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powerpc/mm: Only call store_updates_sp() on stores in do_page_fault()

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Function store_updates_sp() checks whether the faulting
instruction is a store updating r1. Therefore we can limit its calls
to store exceptions.

This patch is an improvement of commit a7a9dcd882 ("powerpc: Avoid
taking a data miss on every userspace instruction miss")

With the same microbenchmark app, run with 500 as argument, on an
MPC885 we get:

Before this patch: 152000 DTLB misses
After this patch:  147000 DTLB misses

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2017-04-19 14:56:24 +02:00 committed by Michael Ellerman
parent 9affa9e228
commit e8de85ca32
1 changed files with 1 additions and 1 deletions
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2
arch/powerpc/mm/fault.c
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@ -287,7 +287,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
* can result in fault, which will cause a deadlock when called with
* mmap_sem held
*/
if (!is_exec && user_mode(regs))
if (is_write && user_mode(regs))
store_update_sp = store_updates_sp(regs);
if (user_mode(regs))