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powerpc: Improve 64bit copy_tofrom_user
Here is a patch from Paul Mackerras that improves the ppc64 copy_tofrom_user. The loop now does 32 bytes at a time and as well as pairing loads and stores. A quick test case that reads 8kB over and over shows the improvement: POWER6: 53% faster POWER7: 51% faster #define _XOPEN_SOURCE 500 #include <stdlib.h> #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <sys/types.h> #include <sys/stat.h> #define BUFSIZE (8 * 1024) #define ITERATIONS 10000000 int main() { char tmpfile[] = "/tmp/copy_to_user_testXXXXXX"; int fd; char *buf[BUFSIZE]; unsigned long i; fd = mkstemp(tmpfile); if (fd < 0) { perror("open"); exit(1); } if (write(fd, buf, BUFSIZE) != BUFSIZE) { perror("open"); exit(1); } for (i = 0; i < 10000000; i++) { if (pread(fd, buf, BUFSIZE, 0) != BUFSIZE) { perror("pread"); exit(1); } } unlink(tmpfile); return 0; } Signed-off-by: Anton Blanchard <anton@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Anton Blanchard
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Benjamin Herrenschmidt
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Feb 17, 2010
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