* Steve Rago <sar@xxxxxxxxxxxx> wrote: > > On Fri, 2009-12-18 at 20:41 +0100, Ingo Molnar wrote: > > * Steve Rago <sar@xxxxxxxxxxxx> wrote: > > > > > > Also, I don't think this needs to have a sysctl, it should just work. > > > > > > The sysctl is a *good thing* in that it allows the eager writeback behavior > > > to be tuned and shut off if need be. I can only test the changes on a > > > finite set of systems, so better safe than sorry. > > > > This issue has been settled many years ago and that's not what we do in the > > Linux kernel. We prefer patches to core code where we are reasonably sure they > > result in good behavior - and then we fix bugs in the new behavior, if any. > > > > (Otherwise odd sysctls would mushroom quickly and the system would become > > untestable in practice.) > > > > Ingo > > I don't disagree, but "that's not what we do" hardly provides insight into > making the judgment call. [...] I gave you an example of the problems that arise, see the last sentence above. > [...] In this case, the variety of combinations of NFS server speed, NFS > client speed, transmission link speed, client memory size, and server memory > size argues for a tunable parameter, because one value probably won't work > well in all combinations. Making it change dynamically based on these > parameters is more complicated than these circumstances call for, IMHO. So having crappy tunables is the reason to introduce even more tunables? I think you just gave a good second example of why we dont want sysctls for features like this. Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
