On Tue, Mar 13, 2007 at 06:41:05PM +0300, Pavel Emelianov wrote: > >>> 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.
fine, nobody actually uses atomic_add_unless(), or am I missing something? using two locks will be slower than using a single lock, adding a loop which counts from 0 to 100 will eat up some cpu, so what? don't do it :) > >> 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. I can happily add him to every email I reply to, but he definitely isn't removed by my mailer (as I already stated, it might be the mailing list which does this), fact is, the email arrives here without him in the cc, so a reply does not contain it either ... best, Herbert - 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/
