IBM pSeries - Manuals

IBM pSeries – Manual in PDF format online.

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Manual IBM pSeries

Summary

Page 5 - Tunables and settings for switch software

pshpstuningguidewp040105.doc Page 5 2.0 Tunables and settings for switch software To optimize the HPS, you can set shell variables for Parallel Environment MPI-based workloads and for IP-based workloads. This section reviews the shell variables that are most often used for performance tuning. For a ...

Page 9 - Tunables and settings for AIX 5L; Parameter; ipforwarding 1

pshpstuningguidewp040105.doc Page 9 rfifosize 0x1000000 receive fifo size False rpoolsize 0x02000000 IP receive pool size True spoolsize 0x02000000 IP send pool size True 3.0 Tunables and settings for AIX 5L Several settings in AIX 5L impact the performance of the HPS. These include the IP and memor...

Page 10 - svmon and vmstat commands

pshpstuningguidewp040105.doc Page 10 The overhead in maintaining the file cache can impact the performance of large parallel applications. Much of the overhead is associated with the sync() system call (by default, run every minute from the syncd daemon). The sync() system call scans all of the page...

Page 13 - place. In that case, it is a good idea to run the svmon command; Large page sizing

pshpstuningguidewp040105.doc Page 13 statistics in 5-second intervals, with the first set of statistics being the statistics since the node or LPAR was last booted. vmstat 5 The pi and po of the page group is the number of 4KB pages read from and written to the paging device between consecutive samp...

Page 15 - Large pages and IP support

pshpstuningguidewp040105.doc Page 15 3.5 Large pages and IP support One of the most important ways to improve IP performance on the HPS is to ensure that large pages are enabled. Large pages are required to allocate a number of large pages which will used by the HPS IP driver at boot time. Each snX ...

Page 16 - Debug settings in the AIX 5L kernel

pshpstuningguidewp040105.doc Page 16 If you have eight cards for p690 (or four cards for p655), this command also indicates whether you have full memory bandwidth. 3.8 Debug settings in the AIX 5L kernel The AIX 5L kernel has several debug settings that affect the performance of an application. To m...

Page 17 - LoadLeveler daemons; Reducing the number of daemons running

pshpstuningguidewp040105.doc Page 17 4.2 LoadLeveler daemons The LoadLeveler® daemons are needed for MPI applications using HPS. However, you can lower the impact on a parallel application by changing the default settings for these daemons. You can lower the impact of the LoadLeveler daemons by: • R...

Page 18 - Settings for AIX 5L threads

pshpstuningguidewp040105.doc Page 18 SCHEDD_DEBUG = -D_ALWAYS 4.3 Settings for AIX 5L threads Several variables help you use AIX 5L threads to tune performance. These are the recommended initial settings for AIX 5L threads when using HPS. Set them in the /etc/environment file. AIXTHREAD_SCOPE=S AIXT...

Page 19 - Debug settings and data collection tools; CPUs and frequency

pshpstuningguidewp040105.doc Page 19 5.0 Debug settings and data collection tools Several debug settings and data collection tools can help you debug a performance problem on systems using HPS. This section contains a subset of the most common setting changes and tools. If a performance problem pers...

Page 20 - Small Real Mode Address Region on HMC GUI; Physical Real Memory; Deconfigured L3 cache; Service focal point

pshpstuningguidewp040105.doc Page 20 5.3 Affinity LPARs On p690 systems, if you are running with more than one LPAR for each CEC, make sure you are running affinity LPARs. To check affinity between CPU, memory, and HPS links, run the associativity scripts on the LPARs. To check the memory affinity s...

Page 21 - HMC error logging; If the lsswtopol command calls out links as ”; Multiple versions of MPI libraries

pshpstuningguidewp040105.doc Page 21 On the HMC GUI, select Service Applications -> Service Focal Point -> Select Serviceable Events. 5.7 errpt command On AIX 5L, the errpt command lists a summary of system error messages. Some of the HPS subsystem errors are collected by errpt. To find out if...

Page 24 - Dropped switch packets

pshpstuningguidewp040105.doc Page 24 MPCI: sends = 14 MPCI: sendsComplete = 14 MPCI: sendWaitsComplete = 17 MPCI: recvs = 17 MPCI: recvWaitsComplete = 13 MPCI: earlyArrivals = 5 MPCI: earlyArrivalsMatched = 5 MPCI: lateArrivals = 8 MPCI: shoves = 10 MPCI: pulls = 13 MPCI: threadedLockYields = 0 MPCI...

Page 26 - Packets dropped in the ML0 interface

pshpstuningguidewp040105.doc Page 26 To help you isolate the exact cause of packet drops, the ifsn_dump -a command also lists the following debug statistics. If you isolate packet drops to these statistics, you will probably need to contact IBM support. dbg: | sNet_drop 0x00000000 [0] | sRTF_drop 0x...

Page 28 - Packets dropped in the switch hardware

pshpstuningguidewp040105.doc Page 28 MAC WOF (2F870): Bit: 1 [. . .] 5.12.4 Packets dropped in the switch hardware If a packet is dropped within the switch hardware itself (for example, when traversing the link between two switch chips), evidence of the packet drop is on the HMC, where the switch Fe...

Page 30 - AIX 5L trace for daemon activity

pshpstuningguidewp040105.doc Page 30 5.16 AIX 5L trace for daemon activity If you suspect that a system daemon is causing a performance problem on your system, run AIX 5L trace to check for daemon activity. For example, to find out which daemons are taking up CPU time, use the following process: tra...

Page 31 - MPI documentation

pshpstuningguidewp040105.doc Page 31 7.2 MPI documentation Parallel Environment for AIX 5L V4.1.1 Hitchhiker's Guide, SA22-7947-01 Parallel Environment for AIX 5L V4.1.1 Operation and Use, Volume 1, SA22-7948-01 Parallel Environment for AIX 5L V4.1.1 Operation and Use, Volume 2, SA22-7949-01 Paralle...