[Devel] Re: [PATCH 0/9] namespaces: Introduction

[Serge E. Hallyn]

Quoting Eric W. Biederman (ebiederm at xmission.com):
> "Serge E. Hallyn" <serue at us.ibm.com> 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.

Here are the numbers with the basic patchsets.  But I guess I should
do another round with adding 7 more void*'s to represent additional
namespaces.

(intervals are for 95% CI, tests were each run 15 times)

           |  with nsproxy  |   without nsproxy |
kernbench  | 68.90 +/- 0.21 |   69.06 +/- 0.22  |
dbench     | 386.0 +/- 26.6 |   388.4 +/- 21.0  |
tbench     | 391.6 +/- 8.00 |   389.4 +/- 10.95 |

reaim with nsproxy
1 115600.000000 5512.441557
3 246985.712000 9375.780582
5 272309.092000 8029.833742
7 290020.000000 7288.367116
9 298591.580000 5557.531915
11 nan nan
13 nan nan
15 nan nan

reaim without nsproxy
1 110160.000000 5728.697311
3 246985.712000 9375.780582
5 262204.197333 11138.510652
7 288660.000000 6880.898412
9 300631.580000 4351.926692
11 nan nan
13 nan nan
15 nan nan