On Sun, Aug 07, 2011 at 06:30:38PM +0900, Akinobu Mita wrote: > The check_bytes() function is used by slub debugging. It returns a pointer > to the first unmatching byte for a character in the given memory area. > > If the character for matching byte is greater than 0x80, check_bytes() > doesn't work. Becuase 64-bit pattern is generated as below. > > value64 = value | value << 8 | value << 16 | value << 24; > value64 = value64 | value64 << 32; > > The integer promotions are performed and sign-extended as the type of value > is u8. The upper 32 bits of value64 is 0xffffffff in the first line, and > the second line has no effect. > > This fixes the 64-bit pattern generation. Thank you. I'm a bit ashamed about this bug... I introduced this bug, so: Reviewed-by: Marcin Slusarz <marcin.slusarz@xxxxxxxxx> I tested your patch to check if performance improvements of commit c4089f98e943ff445665dea49c190657b34ccffe come from this bug or not. And forunately they aren't - performance is exactly the same. How did you find it? Marcin -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>