KY Srinivasan <kys@xxxxxxxxxxxxx> writes: >> -----Original Message----- >> From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] >> Sent: Thursday, January 19, 2017 6:17 AM >> To: devel@xxxxxxxxxxxxxxxxxxxxxx >> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; >> Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; KY Srinivasan >> <kys@xxxxxxxxxxxxx>; John Stultz <john.stultz@xxxxxxxxxx>; Alex Ng (LIS) >> <alexng@xxxxxxxxxxxxx>; Stephen Hemminger >> <stephen@xxxxxxxxxxxxxxxxxx>; Olaf Hering <olaf@xxxxxxxxx>; Richard >> Cochran <richardcochran@xxxxxxxxx>; Radim Krcmar >> <rkrcmar@xxxxxxxxxx> >> Subject: [PATCH v4 2/2] hv_utils: implement Hyper-V PTP source >> >> With TimeSync version 4 protocol support we started updating system time >> continuously through the whole lifetime of Hyper-V guests. Every 5 seconds >> there is a time sample from the host which triggers do_settimeofday[64](). >> While the time from the host is very accurate such adjustments may cause >> issues: >> - Time is jumping forward and backward, some applications may misbehave. >> - In case an NTP server runs in parallel and uses something else for time >> sync (network, PTP,...) system time will never converge. >> - Systemd starts annoying you by printing "Time has been changed" every 5 >> seconds to the system log. >> >> Instead of doing in-kernel time adjustments offload the work to an >> NTP client by exposing TimeSync messages as a PTP device. Users may now >> decide what they want to use as a source. >> >> I tested the solution with chrony, the config was: >> >> refclock PHC /dev/ptp0 poll 3 precision 1e-9 >> >> The result I'm seeing is accurate enough, the time delta between the guest >> and the host is almost always within [-10us, +10us], the in-kernel solution >> was giving us comparable results. >> >> I also tried implementing PPS device instead of PTP by using not currently >> used Hyper-V synthetic timers (we use only one of four for clockevent) but >> with PPS source only chrony wasn't able to give me the required accuracy, >> the delta often more that 100us. >> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > > Vitaly, > > This patch does not apply. Please rebase and send. > Sure, I'm currently testing v5 which includes the .getcrosststamp() callback support. Will be sending it out shortly. -- Vitaly _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
