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0e36b0d125
Commit a7a9dcd882 ("powerpc: Avoid taking a data miss on every
userspace instruction miss") has shown that limiting the read of
faulting instruction to likely cases improves performance.
This patch goes further into this direction by limiting the read
of the faulting instruction to the only cases where it is likely
needed.
On an MPC885, with the same benchmark app as in the commit referred
above, we see a reduction of about 3900 dTLB misses (approx 3%):
Before the patch:
Performance counter stats for './fault 500' (10 runs):
683033312 cpu-cycles ( +- 0.03% )
134538 dTLB-load-misses ( +- 0.03% )
46099 iTLB-load-misses ( +- 0.02% )
19681 faults ( +- 0.02% )
5.389747878 seconds time elapsed ( +- 0.06% )
With the patch:
Performance counter stats for './fault 500' (10 runs):
682112862 cpu-cycles ( +- 0.03% )
130619 dTLB-load-misses ( +- 0.03% )
46073 iTLB-load-misses ( +- 0.05% )
19681 faults ( +- 0.01% )
5.381342641 seconds time elapsed ( +- 0.07% )
The proper work of the huge stack expansion was tested with the
following app:
int main(int argc, char **argv)
{
char buf[1024 * 1025];
sprintf(buf, "Hello world !\n");
printf(buf);
exit(0);
}
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
[mpe: Add include of pagemap.h to fix build errors]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.