On 11/1/2010 8:35 PM, Michael Ellerman wrote: > On Wed, 2010-10-27 at 12:54 -0400, Chris Metcalf wrote: >> The tile architecture uses this framework for our serial console, >> and our users complain that the delay of up to two seconds feels like >> the machine has gone non-responsive and is disturbing. By contrast, >> a delay of up to half a second feels like just the normal sort of >> delay caused by swapping, network lag, etc. and is not noticeable. >> The overhead is obviously not much greater. > It's 4 times greater. > > We picked 2 seconds because it gave a reasonable trade off between > responsiveness and load. I'm not convinced that half a second is a > better number.
Perhaps the tradeoff should be tunable, then? I think on our architecture we're willing to pay a higher cost on the core running this task, since we have many cores; we often have a core that mostly just runs miscellaneous Linux administrative tasks anyway, so adding a bit more overhead there is not significant for us. This issue has caused multiple reports of unresponsiveness from our users, so I'd be interested in finding a way to strike a balance. We could use a config option defaulting to 2 seconds (for example), or something more dynamic (probably unnecessary). Let me know your preference, if this sounds plausible, and I'll write up a proposed patch. Thanks. -- Chris Metcalf, Tilera Corp. http://www.tilera.com _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
