On Sun, 13 Mar 2011, George Spelvin wrote: > Cache aligning the secret[] buffer makes copying from it infinitesimally > more efficient. > --- > drivers/char/random.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/char/random.c b/drivers/char/random.c > index 72a4fcb..4bcc4f2 100644 > --- a/drivers/char/random.c > +++ b/drivers/char/random.c > @@ -1417,8 +1417,8 @@ static __u32 twothirdsMD4Transform(__u32 const buf[4], __u32 const in[12]) > #define HASH_MASK ((1 << HASH_BITS) - 1) > > static struct keydata { > - __u32 count; /* already shifted to the final position */ > __u32 secret[12]; > + __u32 count; /* already shifted to the final position */ > } ____cacheline_aligned ip_keydata[2]; > > static unsigned int ip_cnt; I'm intrigued: please educate me. On what architectures does cache- aligning a 48-byte buffer (previously offset by 4 bytes) speed up copying from it, and why? Does the copying involve 8-byte or 16-byte instructions that benefit from that alignment, rather than cacheline alignment? Thanks, Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>