>>> PS: atomic_add_unless() didn't exist back then >>> (at least I think so) but that might be an option >>> too ... >> I think as far as having this discussion if you can remove that race >> people will be more willing to talk about what vserver does. > > well, shouldn't be a big deal to brush that patch up > (if somebody actually _is_ interested) > >> That said anything that uses locks or atomic operations (finer grained >> locks) because of the cache line ping pong is going to have scaling >> issues on large boxes. > > right, but atomic ops have much less impact on most > architectures than locks :)
Right. But atomic_add_unless() is slower as it is essentially a loop. See my previous letter in this sub-thread. >> So in that sense anything short of per cpu variables sucks at scale. >> That said I would much rather get a simple correct version without the >> complexity of per cpu counters, before we optimize the counters that >> much. > > actually I thought about per cpu counters quite a lot, and > we (Llinux-VServer) use them for accounting, but please > tell me how you use per cpu structures for implementing > limits Did you ever look at how get_empty_filp() works? I agree, that this is not a "strict" limit, but it limits the usage wit some "precision". /* off-the-topic */ Herbert, you've lost Balbir again: In this sub-thread some letters up Eric wrote a letter with Balbir in Cc:. The next reply from you doesn't include him. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
