Re: Default zone_reclaim_mode = 1 on NUMA kernel is bad forfile/email/web servers

[Robert Mueller]

> > I don't think this is any fault of how the software works. It's a
> > *very* standard "pre-fork child processes, allocate incoming
> > connections to a child process, open and mmap one or more files to
> > read data from them". That's not exactly a weird programming model,
> > and it's bad that the kernel is handling that case very badly with
> > everything default.
>
> maybe you incoming connection always happen on one CPU and you do the
> page allocation in that cpu, so some nodes use out of memory but
> others have a lot free. Try bind the child process to different nodes
> might help.

There's are 5000+ child processes (it's a cyrus IMAP server). Neither
the parent of any of the children are bound to any particular CPU. It
uses a standard fcntl lock to make sure only one spare child at a time
calls accept(). I don't think that's the problem.

Rob
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