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Date: Fri, 21 Sep 2012 19:11:05 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: David Miller <davem@...emloft.net> Cc: rick.jones2@...com, subramanian.vijay@...il.com, netdev@...r.kernel.org Subject: Re: [RFC] tcp: use order-3 pages in tcp_sendmsg() On Fri, 2012-09-21 at 13:04 -0400, David Miller wrote: > It's a silly limitation, in net/core/dev.c: > > /* Turn on no cache copy if HW is doing checksum */ > if (!(dev->flags & IFF_LOOPBACK)) { > dev->hw_features |= NETIF_F_NOCACHE_COPY; > if (dev->features & NETIF_F_ALL_CSUM) { > dev->wanted_features |= NETIF_F_NOCACHE_COPY; > dev->features |= NETIF_F_NOCACHE_COPY; > } > } > > Maybe this is probably better done as: > > /* Turn on no cache copy if HW is doing checksum */ > dev->hw_features |= NETIF_F_NOCACHE_COPY; > if (!(dev->flags & IFF_LOOPBACK)) { > if (dev->features & NETIF_F_ALL_CSUM) { > dev->wanted_features |= NETIF_F_NOCACHE_COPY; > dev->features |= NETIF_F_NOCACHE_COPY; > } > } > > And then the code matches more closely the comment. :-) I did a test, and for various combinations (producer/consumer on same core or not, same cpu or not...) and performance is divided by 2 So I guess we can leave the code as is -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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