RedHat NFS client broken with 7.3 kernel 2.4.18-5 ?

Ed Martin ed.martin at iop.org
Mon Aug 5 06:53:01 CDT 2002


Hi,

I have recently been doing some NFS benchmarking and have noticed some odd results.

I've been using bonnie++ v1.02c from a PE1550 and a PE1650, talking to a NetApp filer F820.  I've run a fair few benchmarks now, in different configurations.  Some configurations show a very very sharp drop in performance of certain values.  Rather than the gradual decline displayed by other configurations. 

Sequential output / re-write / K/Sec drops to ~10x worse than it should be
  e.g. 2970 down to 346, or 5730 down to 658
Sequential input / K/Sec drops to ~10x worse than it should be on the 2650
  e.g. 13030 down to 1541

Specifically I see that Red Hat Linux v7.3 with the latest errata kernel (2.4.18-5) has this problem whereas 7.3 with shippping kernel (2.4.18-3) does not!.  Problem seems to occur when the test file is large in comparison with the client RAM (e.g. same size as RAM).  Interestingly the kernel changes text includes the following:
---
 In addition, bugs in the NFS client code have been fixed.

The NFS client in the Red Hat Linux 7.3 clients would negotiate a 32Kb
"window" when connecting to NetApp(tm) filers. This high value caused
several problems in practice.
---

So, I wonder if something else was changed which breaks it?

Has anyone else tried/noticed anything similar?  All thoughts/comments are appreciated.

Yours,

Ed

I attach a few of the key tests which show this.  To translate the attached:
  tweedledee is a PE1550, has 1G of RAM, which was also the bonnie size I used
  hertz is a PE2650, has 2G of RAM, which was also the bonnie size I used
  Both run Red Hat Linux v7.3
    the -3 refers to shipping kernel 2.4.18-3
    -5 refers to the latest 7.3 errata kernel 2.4.18-5
  NFS was using rsize=8192,wsize=8192
  Other NFS client parameters were left at default.
    e.g. proto was UDP



---
Ed Martin
Head of Systems Technology and Support
IOP Publishing Ltd
Dirac House, Temple Back
Bristol  BS1 6BE
ddi: +44 (0)117 930 1102
www:  http://www.iop.org



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