Re: [PATCH 0/9] namespaces: Introduction

From: Eric W. Biederman
Date: Fri May 19 2006 - 05:03:36 EST

"Serge E. Hallyn" <serue@xxxxxxxxxx> writes:

> This patchset introduces a per-process utsname namespace. These can
> be used by openvz, vserver, and application migration to virtualize and
> isolate utsname info (i.e. hostname). More resources will follow, until
> hopefully most or all vserver and openvz functionality can be implemented
> by controlling resource namespaces from userspace.
> Previous utsname submissions placed a pointer to the utsname namespace
> straight in the task_struct. This patchset (and the last one) moves
> it and the filesystem namespace pointer into struct nsproxy, which is
> shared by processes sharing all namespaces. The intent is to keep
> the taskstruct smaller as the number of namespaces grows.

Previously you mentioned:
> BTW - a first set of comparison results showed nsproxy to have better
> dbench and tbench throughput, and worse kernbench performance. Which
> may make sense given that nsproxy results in lower memory usage but
> likely increased cache misses due to extra pointer dereference.

Is this still true? Or did our final reference counting tweak fix
the kernbench numbers?

I just want to be certain that we don't add an optimization,
that reduces performance.

> Changes:
> - the reference count on fs namespace and uts namespace now
> refers to the number of nsproxies pointing to it
> - some consolidation of namespace cloning and exit code to
> clean up kernel/{fork,exit}.c
> - passed ltp and ltpstress on smp power, x86, and x86-64
> boxes.



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