| Message ID | 5020E610.1040808@parallels.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Tue, 2012-08-07 at 13:55 +0400, Pavel Emelyanov wrote: > OK. I was under impression, that hash_ptr was balanced from the fast/effective > perspective, but I can't argue with you in that area :) So, please, consider > the below patch instead of #1 and #2 (the rest ones remain unchanged). > > Thanks, > Pavel > > > From: Pavel Emelyanov <xemul@parallels.com> > Subject: [PATCH 1/5] net: Dont use ifindices in hash fns > > Eric noticed, that when there will be devices with equal indices, some > hash functions that use them will become less effective as they could. > Fix this in advance by mixing the net_device address into the hash value > instead of the device index. > > This is true for arp and ndisc hash fns. The netlabel, can and llc ones > are also ifindex-based, but that three are init_net-only, thus will not > be affected. > > Many thanks to David and Eric for the hash32_ptr implementation! > > Signed-off-by: Pavel Emelyanov <xemul@parallels.com> > --- > include/linux/hash.h | 10 ++++++++++ > include/net/arp.h | 3 ++- > include/net/ndisc.h | 3 ++- > 3 files changed, 14 insertions(+), 2 deletions(-) Signed-off-by: Eric Dumazet <edumazet@google.com> You should resend other patches, since they are no more on http://patchwork.ozlabs.org/project/netdev/list/ -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/hash.h b/include/linux/hash.h index b80506b..24df9e7 100644 --- a/include/linux/hash.h +++ b/include/linux/hash.h @@ -67,4 +67,14 @@ static inline unsigned long hash_ptr(const void *ptr, unsigned int bits) { return hash_long((unsigned long)ptr, bits); } + +static inline u32 hash32_ptr(const void *ptr) +{ + unsigned long val = (unsigned long)ptr; + +#if BITS_PER_LONG == 64 + val ^= (val >> 32); +#endif + return (u32)val; +} #endif /* _LINUX_HASH_H */ diff --git a/include/net/arp.h b/include/net/arp.h index 7f7df93..b630dae 100644 --- a/include/net/arp.h +++ b/include/net/arp.h @@ -3,6 +3,7 @@ #define _ARP_H #include <linux/if_arp.h> +#include <linux/hash.h> #include <net/neighbour.h> @@ -10,7 +11,7 @@ extern struct neigh_table arp_tbl; static inline u32 arp_hashfn(u32 key, const struct net_device *dev, u32 hash_rnd) { - u32 val = key ^ dev->ifindex; + u32 val = key ^ hash32_ptr(dev); return val * hash_rnd; } diff --git a/include/net/ndisc.h b/include/net/ndisc.h index 96a3b5c..980d263 100644 --- a/include/net/ndisc.h +++ b/include/net/ndisc.h @@ -49,6 +49,7 @@ enum { #include <linux/types.h> #include <linux/if_arp.h> #include <linux/netdevice.h> +#include <linux/hash.h> #include <net/neighbour.h> @@ -134,7 +135,7 @@ static inline u32 ndisc_hashfn(const void *pkey, const struct net_device *dev, _ { const u32 *p32 = pkey; - return (((p32[0] ^ dev->ifindex) * hash_rnd[0]) + + return (((p32[0] ^ hash32_ptr(dev)) * hash_rnd[0]) + (p32[1] * hash_rnd[1]) + (p32[2] * hash_rnd[2]) + (p32[3] * hash_rnd[3]));