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aix_tuning.md

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PowerVC

Can add compute templates which can be used to deploy images.

Tuning

Home Node

  • home node is core that a VP first gets dispatched to
  • will try to use home node where possible

Processor Folding

p5/6 Stack Then Spread

  • p5/6 loads 1st & 2nd SMT to ~80% before unfolding next VP

p7 Spread Then Stack (Raw Throughput Mode)

  • p7 loads first thread to 50% then unfolds next VP
  • when all VPs unfolded, starts using 2nd SMT thread
  • when all 2nd threads loaded, starts using tertiaries
  • provides highest throughput at expense of more cores

Notes

  • both report same physical usage
  • more cores using in p7
  • idle time higher
  • reduce VPs accordingly

Scaled Throughput

  • behaves more like P6 - not recommended; try to reduce VPs instead
  • schedo -p -o vpm_throughput_mode=blah

SMT

  • SMT threads go with VPs
  • p5/6 SMT thread can go to 100%
  • p7 SMT thread can only go up to 63%
  • if only primary SMT threads are being used, you have too many VPs

Entitlement

  • If ent not long enough, VPs spend a lot of time warming cache
  • put this somewhere between peak and average

VPs

  • don't set num VPs higher than cores in processor pool

Commands

  • lparstat, pool size, available in pool, virt context switches, phantom interrupts (vm dispatched to core, then ceeded on IO, but after IO interrupt comes back when target VM not running)
  • sar -mu -PALL vertically, all threads with, physc & %entc
  • mpstat -s shows procs horizontally
  • vmstat -IW 60 2 columns:
    • p threads waiting for IO to raw
    • w column is how many threads waiting for CIO/DIO.

Memory

  • %comp > 97% means you page
  • comp is also called dynamic or working storage
  • lssrad -av shows local/near memory for cpus

Paging

  • try to avoid paging in first place
  • use multiple, all same size on different disks
  • lru_file_repage=0 (restricted in AIX7) means care only about minperm
  • on AIX 5.3TL4, should set maxperm & maxperm to 90, only change them with PMR
  • page_steal_method default is 0. 1 means scan only filesystem pages, reduces scanning time. When combined with CIO can make a big difference.

vmstat -v don't want to see high IO blocked

  • numperm = numclient + jfs and other stuff
  • numclient jfs2 & network
  • if numperm == numclient then it is all being used by network or jfs2
  • pbuf is where IO initially gets built
  • vmstat -v | grep memory find number of memory pools
  • minfree & maxfree apply to memory pools
  • vmstat fre column needs to be divided amongst memory pools