On Fri, 02 Mar 2007 17:34:31 -0500 Rik van Riel <[EMAIL PROTECTED]> wrote:
> >>>> The main reason they end up pounding the LRU locks is the > >>>> swappiness heuristic. They scan too much before deciding > >>>> that it would be a good idea to actually swap something > >>>> out, and with 32 CPUs doing such scanning simultaneously... > >>> What kernel version? > >> Customers are on the 2.6.9 based RHEL4 kernel, but I believe > >> we have reproduced the problem on 2.6.18 too during stress > >> tests. > > > > The prev_priority fixes were post-2.6.18 > > We tested them. They only alleviate the problem slightly in > good situations, but things still fall apart badly with less > friendly workloads. What is it with vendors finding MM problems and either not fixing them or kludging around them and not telling the upstream maintainers about *any* of it? > >> I have no reason to believe we should stick our heads in the > >> sand and pretend it no longer exists on 2.6.21. > > > > I have no reason to believe anything. All I see is handwaviness, > > speculation and grand plans to rewrite vast amounts of stuff without even a > > testcase to demonstrate that said rewrite improved anything. > > Your attitude is exactly why the VM keeps falling apart over > and over again. > > Fixing "a testcase" in the VM tends to introduce problems for > other test cases, ad infinitum. In that case it was a bad fix. The aim is to fix known problems without introducing regressions in other areas. A perfectly legitimate approach. You seem to be saying that we'd be worse off if we actually had a testcase. > There's a reason we end up > fixing the same bugs over and over again. No we don't. > I have been looking through a few hundred VM related bugzillas > and have found the same bugs persist over many different > versions of Linux, sometimes temporarily fixed, but they seem > to always come back eventually... > > > None of this is going anywhere, is is it? > > I will test my changes before I send them to you, but I cannot > promise you that you'll have the computers or software needed > to reproduce the problems. I doubt I'll have full time access > to such systems myself, either. > > 32GB is pretty much the minimum size to reproduce some of these > problems. Some workloads may need larger systems to easily trigger 32GB isn't particularly large. Somehow I don't believe that a person or organisation which is incapable of preparing even a simple testcase will be capable of fixing problems such as this without breaking things. - 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/