| Message ID | 1275601036.2533.63.camel@edumazet-laptop |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, 03 Jun 2010 23:37:16 +0200 Eric Dumazet <eric.dumazet@gmail.com> wrote: > Le jeudi 03 juin 2010 __ 23:13 +0200, Eric Dumazet a __crit : > > > MTU=9000 on a system with 4K pages... Oh well... > > > > maybe net/ipv6/mcast.c should cap dev->mtu to PAGE_SIZE-128 or > > something, so that order-0 allocations are done. > > > > > > Something like this patch (completely untested) : > > [PATCH] ipv6: avoid high order allocations > > With mtu=9000, mld_newpack() use order-2 GFP_ATOMIC allocations, that > are very unreliable, on machines where PAGE_SIZE=4K > > Limit allocated skbs to be at most one page. (order-0 allocations) > Maybe - I wouldn't know how desirable that is from the imapct-on-efficiency POV. But I think most failures I've seen are for regular old tcpipv4. Often with e1000, which does larger-than-needed allocations for (iirc) weird alignment requirements. > --- > net/ipv6/mcast.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c > index 59f1881..3484794 100644 > --- a/net/ipv6/mcast.c > +++ b/net/ipv6/mcast.c > @@ -1356,7 +1356,10 @@ static struct sk_buff *mld_newpack(struct net_device *dev, int size) > IPV6_TLV_PADN, 0 }; > > /* we assume size > sizeof(ra) here */ > - skb = sock_alloc_send_skb(sk, size + LL_ALLOCATED_SPACE(dev), 1, &err); > + size += LL_ALLOCATED_SPACE(dev); > + /* limit our allocations to order-0 page */ > + size = min(size, SKB_MAX_ORDER(0, 0)); > + skb = sock_alloc_send_skb(sk, size, 1, &err); > > if (!skb) > return NULL; An alternative which retains any performance benefit from the order-2 allocation would be: p = alloc_pages(__GFP_NOWARN|..., 2); if (!p) p = alloc_pages(..., 0); if you see what I mean. This would also fix any retry/timeout-related stalls which people might experience when the order-2 allocation fails, so it might make things better in general. -- 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
From: Eric Dumazet <eric.dumazet@gmail.com> Date: Thu, 03 Jun 2010 23:37:16 +0200 > [PATCH] ipv6: avoid high order allocations > > With mtu=9000, mld_newpack() use order-2 GFP_ATOMIC allocations, that > are very unreliable, on machines where PAGE_SIZE=4K > > Limit allocated skbs to be at most one page. (order-0 allocations) > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> This looks perfectly fine to me, except I had to change min(...) to min_t(int, ...) to avoid a compile warning. Thanks Eric! -- 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/ipv6/mcast.c b/net/ipv6/mcast.c index 59f1881..3484794 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -1356,7 +1356,10 @@ static struct sk_buff *mld_newpack(struct net_device *dev, int size) IPV6_TLV_PADN, 0 }; /* we assume size > sizeof(ra) here */ - skb = sock_alloc_send_skb(sk, size + LL_ALLOCATED_SPACE(dev), 1, &err); + size += LL_ALLOCATED_SPACE(dev); + /* limit our allocations to order-0 page */ + size = min(size, SKB_MAX_ORDER(0, 0)); + skb = sock_alloc_send_skb(sk, size, 1, &err); if (!skb) return NULL;