On venerdì 20 aprile 2007, Jeff Dike wrote: > On Thu, Apr 19, 2007 at 09:13:46PM -0500, Gregory Smith wrote: > > The primary problem I face with your patch is that the timer ticks are > > not interrupting at even intervals. While things /do/ work the way we > > discussed, the clock was slipping all over the place. Sleeps inside > > the VM were in sync and preserved when the VM was paused, but their > > real-time value was intrinsically unreliable. > > I saw the same thing, if I understand what you mean. I was seeing > very irregular intervals, including the host clock going backwards on > occasion.
> Although, now that I'm thinking about it, some of the irregularity > might be due to how UML handles signals. They're not actually > blocked. When signals aren't allowed, a flag is set saying that, the > signals arrive as usual, except they don't go any further, except to > set another flag that says that they happened. When signals are > enabled, this flag is checked, and the actual handling happens. > > This might make timers less regular, but it doesn't explain the host > gettimeofday going backwards. That may be partially related to timer sources contributing for sub-HZ resolution, if they are not reliable (say TSC), or to problems in old host timer code. In *2004* Ottawa Linux Symposium proceedings I read (on a paper by John Stultz) that sub-sources are used only to interpolate between jiffies ticks, which means that at each timer tick the host clock may go backwards; the fix (a rewrite of the timing subsystem) is related with HRT, and I don't know the current status not which host kernel you are using. -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ User-mode-linux-user mailing list User-mode-linux-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-user
