> > Why is Kyle than suggesting that I am lucky because I have no L2 cache > > (and therefore, Linux runs faster)? > > > > Why are people talking here about flushing 32MB or 64MB L2 on fork()? > > > > Or is it that you need to flush only L1 cache but the architecture forces > > flush of both caches? > > There's only a couple of flush instructions: fic and fdc ... they have > to flush all caches. We did argue the toss on this with the HP > processor people since aliasing, which is primarily where we need > flushes for control, only occurs in the L1 cache. However, they pointed > out that if they made fic and fdc L1 specific, we'd have no control over > DMA type ops which have to reach physical memory. > > > I'd still like to see if someone with PA8800 or PA8900 with L2 ran that > > shared memory experiment to actually *prove* that L2 is physically indexed > > and that the L1 equivalency modulus is 4MB. I.e. not rely on what you > > heard somewhere, but rely on what you see. > > We already did all of that years ago just trying to make the pa8x00 If it is really proved, OK. So, the CPU takes a hash of bits some bits up to 4MB and uses them to calculate an index into 4-way not-power-of-two-sized L1 cache? > chips work with linux ... they didn't for about 18 months. > > James Unfortunatelly, I still get some userspace crashes on SMP, I already found one reproducible crash (running "make install" on gcc-4.5.1). The crash happens with some probability, but the probability is high enough so that it's reproducible. Do you have some idea where cache flushing is missing so that I could try if it fixes my case? BTW. if you flush cache on kmap, I think it couldn't work in multithreaded environment at all --- i.e. the program has "int a, b;" both variables share the cacheline, one thread is accessing "a" via kmap and the other thread writes to b directly, for example "b = 5". Then, cache flushing won't help and one of the variables will be trashed. You need kmap address to be congruent with the linear address. But I think it's not reason for my crash because neither gmake nor bash (that crashes) is multithreaded. Mikulas -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
