On Wed, 2007-11-28 at 14:13 +0000, Luís Henriques wrote: > Hi! Just my 5 cents (or even less!)... > > I am not very familiar with PI-related code but I believe that at least your > 1st assumption is not correct, i.e., the number of boost and unboost is not > necessarily equal. If you have, for example, a task which priority is boost > several times in a row (without releasing the resource), it will only unboost > once -- when the resource is released. Thus, the boost/unboost relation is > not one-to-one but many-to-one ;) > Well of course! That makes perfect sense. Thx, -PWM > Note again that I am not very familiar with this code but I believe this is > the default behaviour of the kernel. > > Hope this helps you understand the problem... > -- > Luís Henriques > > > My expectation would be that all three counters would be more or less > > the same. Further, that we would only boost non-RT tasks in contention > > with an RT task. Is that a wrong assumption? The code seems to imply > > that we boost anyone. > > > > The samples were taken after a reboot followed by a 'make' in an already > > built kernel tree. The counts (gradually) grow in this proportion as > > time/load passes. They are currently low due to the reboot. > > > > What got me started on this path was noticing the context switch counts > > go extremely high with the addition of a single process. Here is the > > output of a silly little program I wrote that reads /proc/stat and calcs > > context-switches/second: > > > > prev: 1990167, current: 1992750, diff: 516/s > > prev: 1992755, current: 1994567, diff: 362/s > > prev: 1994569, current: 1997847, diff: 655/s > > prev: 1997849, current: 2011904, diff: 2811/s # make start > > prev: 2011913, current: 2041192, diff: 5855/s > > prev: 2041194, current: 2074749, diff: 6711/s > > prev: 2074752, current: 2107060, diff: 6461/s > > prev: 2107065, current: 2139376, diff: 6462/s > > prev: 2139378, current: 2164268, diff: 4978/s # make killed > > prev: 2164274, current: 2166674, diff: 480/s > > prev: 2166676, current: 2168187, diff: 302/s > > prev: 2168189, current: 2169576, diff: 277/s > > > > Factor of 10x for a single make (no -j) on an otherwise idle system. > > Again, this was on an already built kernel tree and taken shortly after > > the a previous make invocation (implying the caches should be warm). > > Since I'm hitting on the dcache and inode spin locks (that are now > > rt_spin_locks) and only contending with other system processes (syslog, > > etc) I'm at a loss attempting to understand why the dramatic increase in > > the context switch rate. > > > > Any insights appreciated.... > > > > Thx, > > -PWM > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" > > in the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > - > To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
