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: Wed, 20 Feb 2013 09:39:46 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: Johannes Berg <johannes@...solutions.net> Cc: Marc MERLIN <marc@...lins.org>, David Miller <davem@...emloft.net>, Larry.Finger@...inger.net, bhutchings@...arflare.com, linux-wireless@...r.kernel.org, netdev@...r.kernel.org Subject: Re: 3.7.8/amd64 full interrupt hangs due to iwlwifi under big nfs copies out On Wed, 2013-02-20 at 17:59 +0100, Johannes Berg wrote: > Yeah, I don't follow netdev much any more... > Short answer : tcp stack has autotuning sk_rcvbuf, tracking _memory_ use of a socket. If network layer provides 8k fat skbs (holding 1500 bytes), the advertised TCP receive window will be much smaller than if network layer provides 2k skbs. Its quite visible in a tcpdump in the beginning of a tcp session. You'll see how linux grows the receive window, before and after my patch. You'll see how the sender can send its data faster. Providing nice skbs is a way to speedup Internet browsing, as most http traffic happen exactly while tcp receiver didnt yet advertised a big window. (Especially visible with large RTT) > > > > /* If frame is small enough to fit in skb->head, pull it completely. > > * If not, only pull ieee80211_hdr so that splice() or TCP coalesce > > * are more efficient. > > */ > > Oh, right, though I guess the comment is now wrong since practically > every packet will be copied either here or in mac80211 (A-MSDUs are > split up there) Comment is not 'wrong', it describes what happens here. If there is enough room in skb->head to avoid attaching a page fragment to the skb, lets copy the frame so that the page fragment can be reused by the NIC driver immediately. -- 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