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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

memory subsystems. The following sections provide a brief overview of the most commonly

used tunables. For more information about these subjects, see the AIX 5L tuning manuals listed

in section 7.0.

3.1 IP tunables

When defining subnets for HPS links, it is easier to debug performance problems if there is only

one HPS interface for each IP subnet. When running with multiple interfaces for each subnet,

applications do not typically control which interface is used to send or receive packets. This can

make connectivity problems more difficult to debug. For example, the RSCT cthats subsystem

that polls interfaces to assert connectivity might have problems identifying which interfaces are

down when multiple interfaces are on the same IP subnet.

The IP subsystem has several variables that impact IP performance over HPS. The following

table contains recommended initial settings used for TCP/IP. For more information about these

variables, see the AIX 5L manuals listed in section 7.0.

Parameter Setting

sb_max 1310720

tcp_sendspace 655360

tcp_recvspace 655360

rfc1323 1

tcp_mssdflt 1448

ipforwarding 1

3.2 File cache

AIX 5L defines all virtual memory pages allocated for most file systems as permanent storage

pages. Files mapped from the GPFS file cache are an exception. A subset of permanent storage

pages are further defined as client pages (such as NFS and JFS2 mapped files). All permanent

storage pages can be referred to as the file cache. The size of the file cache tends to grow unless

an increase in computational page allocations (for example, application data stored in memory)

causes the operating system to run low on available virtual memory frames, or the files being

memory mapped become unavailable (for example, a file system becomes unmounted).

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IBM pSeries User Manual Page 9