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: Tue, 20 Jul 2010 08:57:38 -0400 From: Brian Bloniarz <bmb@...enacr.com> To: Tom Herbert <therbert@...gle.com> CC: Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org Subject: Re: Very low latency TCP for clusters Tom Herbert wrote: > On Mon, Jul 19, 2010 at 3:03 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: >> Le lundi 19 juillet 2010 à 11:44 -0700, Tom Herbert a écrit : >> >>> I see about 7 usecs as best number on loopback, so I believe this is >>> in the ballpark. As I mentioned above, this about "best case" latency >>> of a single thread, so we assume any amount of pinning or other >>> customized configuration to that purpose. >> Well, given I get 29 us on a ping between two machines (Gb link, no >> process involved on receiver, only softirq), I really doubt we can reach >> 5 us on a tcp test involving a user process on both side ;) >> > That's pretty pokey ;-) I see numbers around 25 usecs between to > machines, this is with TCP_NBRR. With TCP_RR it's more like 35 usecs, > so eliminating the scheduler is already a big reduction. That leaves > 18 usecs in device time, interrupt processing, network, and cache > misses; 7 usecs in TCP processing, user space. While 5 usecs is an > aggressive goal, I am not ready to concede that there's an > architectural limit in either NICs, TCP, or sockets that can't be > overcome. Have you toyed with the NIC's interrupt coalescing yet? I'm wondering if any part of the 25usecs is that. -- 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