Arjan van de Ven <[EMAIL PROTECTED]> writes: > On Sun, 2007-07-15 at 19:17 +0200, Bodo Eggert wrote: >> Matt Mackall <[EMAIL PROTECTED]> wrote: >> > On Fri, Jul 13, 2007 at 03:20:54PM +0200, Rene Herman wrote: >> >> >> As far as I'm aware, the actual reason for 4K stacks is that after the >> >> system has been up and running for some time getting "1 physically >> >> contiguous pages" becomes significantly easier than 2 which wouldn't be >> >> arbitrary. >> > >> > If there are exactly two free pages in the system, the odds of them >> > being buddies (ie adjacent AND properly aligned) is quite small. The >> > available page pool has to grow quite a bit before the availability of >> > order-1 page pairs approaches 100%. >> >> If there are exactly two free pages in a system, the odds of starting any >> program are not very good. You'll have to swap, and if you do, you can swap >> two more pages in order to free enough RAM for the stack. > > even if you have several thousand pages the odds aren't good; or rather, > they start out reasonably ok until something starts eating very > deliberately at the 8k pages pool, for example the new app creating > about 10 threads.... > > The 4K issue is "tricky", only a few selected workload/compiler combos > seem to hit the dirt, yet distros like Fedora and RHEL use 4K stacks > since forever, and if it gave massive problems they wouldn't do that. > On the upside, especially on very-threaded workloads, it helps > reliability and the VM a lot...
I guess no Fedora users run md+lvm+xfs then. That combination has quite reliably crashed any 4k-stack kernel I've ever cared to try. -- Måns Rullgård [EMAIL PROTECTED] - 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/
