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The average string that is copied from user space to kernel space is rather short. E.g. booting a system involves about 50.000 strncpy_from_user() calls where the NULL terminated string has an average size of 27 bytes. By default our s390 specific strncpy_from_user() implementation however copies up to 4096 bytes, which is a waste of cpu cycles and cache lines. Therefore reduce the default length to L1_CACHE_BYTES (256 bytes), which also reduces the average execution time of strncpy_from_user() by 30-40%. Alternatively we could have switched to the generic strncpy_from_user() implementation, however it turned out that that variant would be slower than the now optimized s390 variant. Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> |
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| .. | ||
| delay.c | ||
| find.c | ||
| Makefile | ||
| mem.S | ||
| probes.c | ||
| spinlock.c | ||
| string.c | ||
| uaccess.c | ||
| xor.c | ||