user/sven/linux.git/arch/powerpc/lib/string_64.S, branch v4.4.27

powerpc: Exported functions __clear_user and copy_page use r2 so need _GLOBAL_TOC()

2014-06-05T03:20:41Z

__clear_user and copy_page load from the TOC and are also exported to modules. This means we have to use _GLOBAL_TOC() so that we create the global entry point that sets up the TOC. Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt

powerpc: Optimise the 64bit optimised __clear_user

2012-07-03T04:14:48Z

I blame Mikey for this. He elevated my slightly dubious testcase: to benchmark status. And naturally we need to be number 1 at creating zeros. So lets improve __clear_user some more. As Paul suggests we can use dcbz for large lengths. This patch gets the destination cacheline aligned then uses dcbz on whole cachelines. Before: 10485760000 bytes (10 GB) copied, 0.414744 s, 25.3 GB/s After: 10485760000 bytes (10 GB) copied, 0.268597 s, 39.0 GB/s 39 GB/s, a new record. Signed-off-by: Anton Blanchard Tested-by: Olof Johansson Acked-by: Olof Johansson Signed-off-by: Benjamin Herrenschmidt

powerpc: 64bit optimised __clear_user

2012-07-03T04:14:41Z

I noticed __clear_user high up in a profile of one of my RAID stress tests. The testcase was doing a dd from /dev/zero which ends up calling __clear_user. __clear_user is basically a loop with a single 4 byte store which is horribly slow. We can do much better by aligning the desination and doing 32 bytes of 8 byte stores in a loop. The following testcase was used to verify the patch: http://ozlabs.org/~anton/junkcode/stress_clear_user.c To show the improvement in performance I ran a dd from /dev/zero to /dev/null on a POWER7 box: Before: # dd if=/dev/zero of=/dev/null bs=1M count=10000 10485760000 bytes (10 GB) copied, 3.72379 s, 2.8 GB/s After: # time dd if=/dev/zero of=/dev/null bs=1M count=10000 10485760000 bytes (10 GB) copied, 0.728318 s, 14.4 GB/s Over 5x faster. Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt