| Message ID | 4B2933FC.7070306@ixiacom.com |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
Le 16/12/2009 20:24, Lucian Adrian Grijincu a écrit : > > On SMP, when ports are not allocated randomly, using the same starting > port on all processors will lead to bad performance as all processors > will try to get the same hashbucket spinlock: only one will succeed, > the rest will spin madly. > > We solve this problem by making each processor start searching from a > different port. To not skip possibly valid port ranges we renormalize > the hint value too. > > Signed-off-by: Lucian Adrian Grijincu <lgrijincu@ixiacom.com> > --- > net/ipv4/udp.c | 12 +++++++++--- > 1 files changed, 9 insertions(+), 3 deletions(-) > > This makes no sense. You correct a bad performance issue bringed by your previous patch ? Please submit one patch, with no performance regression. I suggest you use a per_cpu hint if you really want to be fast... Thanks -- 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/net/ipv4/udp.c b/net/ipv4/udp.c index f437d9d..5d17c71 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -219,7 +219,9 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum, first = (((u64)rand * remaining) >> 32) + low; } else { rand = 1; - first = hint; + first = hint + smp_processor_id(); + if (first > high) + first = low + (first - low) % remaining; } /* * force rand to be an odd multiple of UDP_HTABLE_SIZE @@ -243,8 +245,12 @@ int udp_lib_get_port(struct sock *sk, unsigned short snum, do { if (low <= snum && snum <= high && !test_bit(snum >> udptable->log, bitmap)) { - if (unlikely(!sysctl_udp_port_randomization)) - hint = snum; + if (unlikely(!sysctl_udp_port_randomization)) { + int cur_hint = snum - smp_processor_id(); + if (cur_hint < low) + cur_hint = high - (low - cur_hint) % remaining; + hint = cur_hint; + } goto found; } snum += rand;
On SMP, when ports are not allocated randomly, using the same starting port on all processors will lead to bad performance as all processors will try to get the same hashbucket spinlock: only one will succeed, the rest will spin madly. We solve this problem by making each processor start searching from a different port. To not skip possibly valid port ranges we renormalize the hint value too. Signed-off-by: Lucian Adrian Grijincu <lgrijincu@ixiacom.com> --- net/ipv4/udp.c | 12 +++++++++--- 1 files changed, 9 insertions(+), 3 deletions(-)