Re: kern/45626: System time does not advance correctly when noatime is specified for /var

[Donald Allen <donaldcallen%gmail.com@localhost>]

The following reply was made to PR kern/45626; it has been noted by GNATS.

From: Donald Allen <donaldcallen%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: kern/45626: System time does not advance correctly when noatime
 is specified for /var
Date: Fri, 18 Nov 2011 08:23:16 -0500

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 On Thu, Nov 17, 2011 at 3:25 PM, <gnats-admin%netbsd.org@localhost> wrote:
 
 > Thank you very much for your problem report.
 > It has the internal identification `kern/45626'.
 > The individual assigned to look at your
 > report is: kern-bug-people.
 >
 > >Category:       kern
 > >Responsible:    kern-bug-people
 > >Synopsis:       System time does not advance correctly when noatime is
 > specified for /var
 > >Arrival-Date:   Thu Nov 17 20:25:00 +0000 2011
 >
 
 It turns out that my attributing the cause of this problem to the use of
 noatime in mounting /var is not correct. I tried booting the system several
 times with and without the noatime option for /var and got perfect
 correlation with the timer behaving incorrectly and not. But with /var
 mounted without noatime, I began using the system and after it had been up
 for hours, I noticed last night that the clock had gone catatonic, was
 exhibiting the same advancing-at-a-snail's-pace behavior that prompted this
 report.
 
 I had an exchange of emails with Christos Zoulas about this. Christos
 suggested running
 
 sysctl -a | grep kern.timecounter
 
 which I did:
 
 kern.timecounter.choice = TSC(q=3000, f=67750617510 Hz) clockinterrupt(q=0,
 f=100 Hz) ichlpcib0(q=1000, f=3579545 Hz) hpet0(q=2000, f=14318179 Hz)
 ACPI-Fast(q=1000, f=3579545 Hz) lapic(q=-100, f=266097187 Hz) i8254(q=100,
 f=1193182 Hz) dummy(q=-1000000, f=1000000 Hz)
 kern.timecounter.hardware = TSC
 kern.timecounter.timestepwarnings = 0
 
 He also suggested trying
 
 sysctl -w kern.timecounter.hardware=hpet0
 >
 > and see if that fixes it.
 >
 
 It does:
 
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:36 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:36 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:36 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:36 EST 2011
 root@salome:/home/dca$ sysctl -w kern.timecounter.hardware=hpet0
 kern.timecounter.hardware: TSC -> hpet0
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:40 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:41 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:42 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:43 EST 2011
 root@salome:/home/dca$ date
 Thu Nov 17 17:53:44 EST 2011
 root@salome:/home/dca$
 
 However, after doing this, the system behaved in odd ways. I had trouble
 shutting X down, the system seemed not to be hearing the (USB) keyboard (I
 couldn't log in after doing ctrl-alt-f2). I finally got it shut down and
 rebooted, ending this experiment.
 
 I then decided to try a newer kernel, and installed the kernel from the
 11/17 snapshot. Upon booting the system this morning (with all the file
 systems, including /var, mounted async,noatime), I quickly observed the
 clock problem.
 
 I cannot use this system because of this problem, but I will leave NetBSD
 installed, so if any further information is needed (would you like dmesg
 output?), or further experimentation, it will be available and I will
 provide whatever help I can.
 
 /Don
 
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 Content-Type: text/html; charset=ISO-8859-1
 Content-Transfer-Encoding: quoted-printable
 
 <br><br><div class=3D"gmail_quote">On Thu, Nov 17, 2011 at 3:25 PM,  <span =
 dir=3D"ltr">&lt;<a href=3D"mailto:gnats-admin%netbsd.org@localhost"; 
target=3D"_blank"=
 >gnats-admin%netbsd.org@localhost</a>&gt;</span> wrote:<br><blockquote 
 >class=3D"gmail=
 _quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:=
 1ex">
 
 Thank you very much for your problem report.<br>
 It has the internal identification `kern/45626&#39;.<br>
 The individual assigned to look at your<br>
 report is: kern-bug-people.<br>
 <br>
 &gt;Category: =A0 =A0 =A0 kern<br>
 &gt;Responsible: =A0 =A0kern-bug-people<br>
 &gt;Synopsis: =A0 =A0 =A0 System time does not advance correctly when noati=
 me is specified for /var<br>
 &gt;Arrival-Date: =A0 Thu Nov 17 20:25:00 +0000 2011<br></blockquote><div><=
 br></div><div>It turns out that my attributing the cause of this problem to=
  the use of noatime in mounting /var is not correct. I tried booting the sy=
 stem several times with and without the noatime option for /var and got per=
 fect correlation with the timer behaving incorrectly and not. But with /var=
  mounted without noatime, I began using the system and after it had been up=
  for hours, I noticed last night that the clock had gone catatonic, was exh=
 ibiting the same advancing-at-a-snail&#39;s-pace behavior that prompted thi=
 s report.</div>
 
 <div><br></div><div>I had an exchange of emails with Christos Zoulas about =
 this. Christos suggested running</div><div><br></div><div><meta http-equiv=
 =3D"content-type" content=3D"text/html; charset=3Dutf-8"><span class=3D"App=
 le-style-span" style=3D"border-collapse: collapse; color: rgb(51, 51, 51); =
 font-family: arial, sans-serif; font-size: 13px; ">sysctl -a | grep kern.ti=
 mecounter</span></div>
 <div><span class=3D"Apple-style-span" style=3D"border-collapse: collapse; c=
 olor: rgb(51, 51, 51); font-family: arial, sans-serif; font-size: 13px; "><=
 br></span></div><div><span class=3D"Apple-style-span" style=3D"border-colla=
 pse: collapse; color: rgb(51, 51, 51); font-family: arial, sans-serif; font=
 -size: 13px; ">which I did:</span></div>
 <div><span class=3D"Apple-style-span" style=3D"border-collapse: collapse; c=
 olor: rgb(51, 51, 51); font-family: arial, sans-serif; font-size: 13px; "><=
 br></span></div><div><span class=3D"Apple-style-span" style=3D"border-colla=
 pse: collapse; color: rgb(51, 51, 51); font-family: arial, sans-serif; font=
 -size: 13px; "><meta http-equiv=3D"content-type" content=3D"text/html; char=
 set=3Dutf-8"><span class=3D"Apple-style-span" style=3D"color: rgb(68, 68, 6=
 8); ">kern.timecounter.choice =3D TSC(q=3D3000, f=3D67750617510 Hz) clockin=
 terrupt(q=3D0, f=3D100 Hz) ichlpcib0(q=3D1000, f=3D3579545 Hz) hpet0(q=3D20=
 00, f=3D14318179 Hz) ACPI-Fast(q=3D1000, f=3D3579545 Hz) lapic(q=3D-100, f=
 =3D266097187 Hz) i8254(q=3D100, f=3D1193182 Hz) dummy(q=3D-1000000, f=3D100=
 0000 Hz)<br>
 kern.timecounter.hardware =3D TSC<br>kern.timecounter.timestepwarnings =3D =
 0</span></span></div><div><span class=3D"Apple-style-span" style=3D"border-=
 collapse: collapse; color: rgb(51, 51, 51); font-family: arial, sans-serif;=
  font-size: 13px; "><span class=3D"Apple-style-span" style=3D"color: rgb(68=
 , 68, 68); "><br>
 </span></span></div><div><span class=3D"Apple-style-span" style=3D"border-c=
 ollapse: collapse; color: rgb(51, 51, 51); font-family: arial, sans-serif; =
 font-size: 13px; "><span class=3D"Apple-style-span" style=3D"color: rgb(68,=
  68, 68); ">He also suggested trying=A0</span></span></div>
 <div><span class=3D"Apple-style-span" style=3D"border-collapse: collapse; c=
 olor: rgb(51, 51, 51); font-family: arial, sans-serif; font-size: 13px; "><=
 span class=3D"Apple-style-span" style=3D"color: rgb(68, 68, 68); "><br></sp=
 an></span></div>
 <div><span class=3D"Apple-style-span" style=3D"border-collapse: collapse; c=
 olor: rgb(51, 51, 51); font-family: arial, sans-serif; font-size: 13px; "><=
 span class=3D"Apple-style-span" style=3D"color: rgb(68, 68, 68); "><meta ht=
 tp-equiv=3D"content-type" content=3D"text/html; charset=3Dutf-8"><div class=
 =3D"im" style=3D"color: rgb(51, 51, 51); ">
 <blockquote class=3D"gmail_quote" style=3D"margin-top: 0pt; margin-right: 0=
 pt; margin-bottom: 0pt; margin-left: 0.8ex; border-left-width: 1px; border-=
 left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex=
 ; ">
 sysctl -w kern.timecounter.hardware=3Dhpet0<br><br>and see if that fixes it=
 .<br></blockquote></div><div><br>It does:<br><br>root@salome:/home/dca$ dat=
 e<br>Thu Nov 17 17:53:36 EST 2011<br>root@salome:/home/dca$ date<br>Thu Nov=
  17 17:53:36 EST 2011<br>
 root@salome:/home/dca$ date<br>Thu Nov 17 17:53:36 EST 2011<br>root@salome:=
 /home/dca$ date<br>Thu Nov 17 17:53:36 EST 2011<br>root@salome:/home/dca$ s=
 ysctl -w kern.timecounter.hardware=3Dhpet0<br>kern.timecounter.hardware: TS=
 C -&gt; hpet0<br>
 root@salome:/home/dca$ date<br>Thu Nov 17 17:53:40 EST 2011<br>root@salome:=
 /home/dca$ date<br>Thu Nov 17 17:53:41 EST 2011<br>root@salome:/home/dca$ d=
 ate<br>Thu Nov 17 17:53:42 EST 2011<br>root@salome:/home/dca$ date<br>Thu N=
 ov 17 17:53:43 EST 2011<br>
 root@salome:/home/dca$ date<br>Thu Nov 17 17:53:44 EST 2011<br>root@salome:=
 /home/dca$=A0</div><div><br></div><div>However, after doing this, the syste=
 m behaved in odd ways. I had trouble shutting X down, the system seemed not=
  to be hearing the (USB) keyboard (I couldn&#39;t log in after doing ctrl-a=
 lt-f2). I finally got it shut down and rebooted, ending this experiment.</d=
 iv>
 <div><br></div><div>I then decided to try a newer kernel, and installed the=
  kernel from the 11/17 snapshot. Upon booting the system this morning (with=
  all the file systems, including /var, mounted async,noatime), I quickly ob=
 served the clock problem.</div>
 <div><br></div><div>I cannot use this system because of this problem, but I=
  will leave NetBSD installed, so if any further information is needed (woul=
 d you like dmesg output?), or further experimentation, it will be available=
  and I will provide whatever help I can.</div>
 <div><br></div><div>/Don</div><div><br></div><div><br></div></span></span><=
 /div></div><br>
 
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