diff options
author | Anton Blanchard <anton@samba.org> | 2017-04-03 16:41:02 +1000 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-03-22 09:23:23 +0100 |
commit | 597609c8602285b94d520506a4ee6f7cba582d51 (patch) | |
tree | 473442277bea82b399cd231742dfa5620a746cbd | |
parent | a4898ddf7e18b090d2d31ca9c9d51522d3fad1c2 (diff) |
powerpc: Avoid taking a data miss on every userspace instruction miss
[ Upstream commit a7a9dcd882a67b68568868b988289fce5ffd8419 ]
Early on in do_page_fault() we call store_updates_sp(), regardless of
the type of exception. For an instruction miss this doesn't make
sense, because we only use this information to detect if a data miss
is the result of a stack expansion instruction or not.
Worse still, it results in a data miss within every userspace
instruction miss handler, because we try and load the very instruction
we are about to install a pte for!
A simple exec microbenchmark runs 6% faster on POWER8 with this fix:
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
unsigned long left = atol(argv[1]);
char leftstr[16];
if (left-- == 0)
return 0;
sprintf(leftstr, "%ld", left);
execlp(argv[0], argv[0], leftstr, NULL);
perror("exec failed\n");
return 0;
}
Pass the number of iterations on the command line (eg 10000) and time
how long it takes to execute.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | arch/powerpc/mm/fault.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index a67c6d781c52..d154e333f76b 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c @@ -294,7 +294,7 @@ int __kprobes 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 (user_mode(regs)) + if (!is_exec && user_mode(regs)) store_update_sp = store_updates_sp(regs); if (user_mode(regs)) |