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: Thu, 12 Apr 2018 08:03:49 -0700 From: Richard Cochran <richardcochran@...il.com> To: Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com> Cc: Thomas Gleixner <tglx@...utronix.de>, netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us, vinicius.gomes@...el.com, anna-maria@...utronix.de, henrik@...tad.us, John Stultz <john.stultz@...aro.org>, levi.pearson@...man.com, edumazet@...gle.com, willemb@...gle.com, mlichvar@...hat.com Subject: Re: [RFC v3 net-next 13/18] net/sched: Introduce the TBS Qdisc On Wed, Apr 11, 2018 at 04:38:44PM -0700, Jesus Sanchez-Palencia wrote: > Just breaking this down a bit, yes, TAI is the network time base, and the NICs > PTP clock use that because PTP is (commonly) based on TAI. After the PHCs have > been synchronized over the network (e.g. with ptp4l), my understanding is that > if applications want to use the clockid_t CLOCK_TAI as a network clock reference > it's required that something (i.e. phc2sys) is synchronizing the PHCs and the > system clock, and also that something calls adjtime to apply the TAI vs UTC > offset to CLOCK_TAI. Yes. I haven't seen any distro that sets the TAI-UTC offset after boot, nor are there any user space tools for this. The kernel is ready, though. > I was thinking about the full offload use-cases, thus when no scheduling is > happening inside the qdiscs. Applications could just read the time from the PHC > clocks directly without having to rely on any of the above. On this case, > userspace would use DYNAMIC_CLOCK just to flag that this is the case, but I must > admit it's not clear to me how common of a use-case that is, or even if it makes > sense. 1588 allows only two timescales, TAI and ARB-itrary. Although it doesn't make too much sense to use ARB, still people will do strange things. Probably some people use UTC. I am not advocating supporting alternate timescales, just pointing out the possibility. Thanks, Richard
Powered by blists - more mailing lists