Date: Sun, 18 Jul 2010 09:56:57 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Marius Strobl <marius@alchemy.franken.de> Cc: freebsd-sparc64@FreeBSD.org Subject: Re: [RFC] Event timers on sparc64/sun4v Message-ID: <4C42A5B9.7080901@FreeBSD.org> In-Reply-To: <20100716213503.GT4706@alchemy.franken.de> References: <4C404018.6040405@FreeBSD.org> <20100716213503.GT4706@alchemy.franken.de>
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Marius Strobl wrote: > please don't commit this as-is: > - using the stick instead of the tick counter for machines with CPUs > and thus tick counters running at different speeds has turned out > to be suboptimal, probably due to the fact that the 12.5MHz the > stick counters typically are driven by don't provide sufficient > granularity. Thus the more desireable variant for these machines > probably is to provide the tick counter of the BSP as the only > non-per-CPU timer and forward it to the APs via IPIs. This also > leaves the stick counter of all >= US-III machines generally > available for driving statclock, which likely is also desirable. > - I'd like to keep the tick grace check as this caused problems in > the past. Probably tick_et_start() just should return an error > in this case. > - I don't like wasting CPU cycles for determining whether the > workaround for BlackBird CPUs is needed (assuming #1 above is > implemented so distinguishing stick/tick is no longer needed) > with every (s)tick interrupt which are a lot as this just won't > ever change during runtime, i.e. I'd like to keep the different > interrupt handlers which are set up as needed. > - Replacing intr_disable_all() with intr_disable() on sun4v > probably isn't a good idea as the latter doesn't disable IPIs > as it does on sparc64 and other architectures. Here is new path, updated respecting two last points: http://people.freebsd.org/~mav/timers_sparc2.patch Don't you have some spare system with stick problems, so I could play with it? And some documentation? I am curious, what is wrong there. :) -- Alexander Motin
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