lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 21 Apr 2014 07:23:04 -0700 (PDT) From: Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com> To: netdev@...r.kernel.org Cc: davem@...emloft.net, linux-kernel@...r.kernel.org, Rama Nichanamatlu <rama.nichanamatlu@...cle.com>, Sergey Linetskiy <sergey.linetskiy@...cle.com>, Vadim Makhervaks <vadim.makhervaks@...cle.com>, Guangyu Sun <guangyu.sun@...cle.com> Subject: Performance problem with bond interface We see a performance problem when the slaves of the bond don't support checksum offload features. What we see is tcp_sendmsg's skb_add_data_nocache ending up not using the csum_and_copy_from_user which would have computed the checksum while copying from user buffer to kernel buffer. Instead it computes later in dev_hard_start_xmit when it figures out the slave doesn't support checksum offload and ends up expensive . The bonding interface's "features" has NETIF_F_HW_CSUM (or NETIF_F_NO_CSUM in 2.6.39) set which makes the stack think checksum need not be computed in software. /* * Check whether we can use HW checksum. */ if (sk->sk_route_caps & NETIF_F_ALL_CSUM) skb->ip_summed = CHECKSUM_PARTIAL; But later in dev_hard_start_xmit it finds out the slave does not support checksumming and decides to compute in software. /* If packet is not checksummed and device does not * support checksumming for this protocol, complete * checksumming here. */ if (skb->ip_summed == CHECKSUM_PARTIAL) { skb_set_transport_header(skb, skb_checksum_start_offset(skb)); if (!(features & NETIF_F_ALL_CSUM) && skb_checksum_help(skb)) goto out_kfree_skb; } We see this problem after this commit: commit 1742f183fc218798dab6fcf0ded25b6608fc0a48 Author: MichaÅ<82> MirosÅ<82>aw <mirq-linux@...e.qmqm.pl> Date: Fri Apr 22 06:31:16 2011 +0000 net: fix netdev_increment_features() Simplify and fix netdev_increment_features() to conform to what is stated in netdevice.h comments about NETIF_F_ONE_FOR_ALL. Include FCoE segmentation and VLAN-challedged flags in computation. Signed-off-by: MichaÅ<82> MirosÅ<82>aw <mirq-linux@...e.qmqm.pl> Signed-off-by: David S. Miller <davem@...emloft.net> Prior to that the below code in netdev_increment_features was helping in turning off NETIF_F_NO_CSUM on bond when the slaves don't support it: /* If device needs checksumming, downgrade to it. */ if (all & NETIF_F_NO_CSUM && !(one & NETIF_F_NO_CSUM)) all ^= NETIF_F_NO_CSUM | (one & NETIF_F_ALL_CSUM); The slaves are Mellanox IB adapters. This is on x86_64 platform. Please let us know if you need any additional information. Thanks. Venkat -- 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
Powered by blists - more mailing lists