Messages in this thread | | | Date | Sun, 20 Apr 2008 14:47:17 +0200 | From | Willy Tarreau <> | Subject | Re: x86: 4kstacks default |
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On Sun, Apr 20, 2008 at 02:27:14PM +0200, Andi Kleen wrote: > Adrian Bunk <bunk@kernel.org> writes: > > > > 6k is known to work, and there aren't many problems known with 4k. > > > > And from a QA point of view the only way of getting 4k thoroughly tested > > But you have to first ask why do you want 4k tested? Does it serve > any useful purpose in itself? I don't think so. Or you're saying > it's important to support 50k kernel threads on 32bit kernels?
Clearly if I have the choice between a kernel which can run 50k threads and a kernel which does not crash under me during an I/O error, I choose the later! I don't even imagine what purpose 50k kernel threads may serve. I certainly can understand that reducing memory footprint is useful, but if we want wider testing of 4k stacks, considering they may fail in error path in complex I/O environment, it's not likely during -rc kernels that we'll detect problems, and if we push them down the throat of users in a stable release, of course they will thank us very much for crashing their NFS servers in production during peak hours.
I have nothing against changing the default setting to 4k provided that it is easy to get back to the save setting (ie changing a config option, or better, a cmdline parameter). I just don't agree with the idea of forcing users to swim in the sh*t, it only brings bad reputation to Linux.
What would really help would be to have 8k stacks with the lower page causing a fault and print a stack trace upon first access. That way, the safe setting would still report us useful information without putting users into trouble.
Willy
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