Significant Memory Reduction Using Sharepte Patch on Database Workload

Significant Memory Reduction Using Sharepte Patch on Database Workload

[Peter Wong]

     I used a very heavy database workload to evaluate two kernels:

     (1) 2.5.44-mm2:
         2.5.44 + Andrew Morton's mm2 patch

     (2) 2.5.44-mm2-less-shpte:
         2.5.44 + Andrew Morton's mm2 patch
                - Dave McCracken's shpte-ng.patch

     Andrew' mm2 patch can be found at:
http://www.zipworld.com.au/~akpm/linux/patches/2.5/2.5.44/2.5.44-mm2/.

     Note that Dave's shared pte patch is included in Andrew's mm2
patch. The objective of this comparison is to measure the impact
of Dave's patch.

----------------------------------------------------------------------
System Information:

   - 8-way 700MHz Pentium III Xeon processors, 2MB L2 Cache
   - 4GB RAM
   - 6 SCSI controllers connected to 120 9.1 GB disks with 10K RPM
----------------------------------------------------------------------

     Based upon the performance metrics and CPU utilization, the two
kernels achieve similar performance. However, memory consumption
by rmap and page tables is reduced significantly by using Dave's
patch. Basically, a large number of I/O prefetchers and database
agents can share two small sets of page tables, which in turn
reduce the amount of rmap memory.


                               2.5.44-mm2     2.5.44-mm2-less-shpte
     ==============================================================
     pte_chain  (max) (MB)        1.2                182.3


     PageTables (max) (MB)        5.2                153.0


     In total, we save ~330 MB in the low memory area.

Regards,
Peter

Peter Wai Yee Wong
IBM LTC Performance Team
email: wpeter@us.ibm.com


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