Tuning Redhat Linux OS parameters

[former_member184709]

Hello,

I've been reading the following notes:

Note 487972 - Tuning Livecache to the Linux OS

Note 767635 - MaxDB Version 7.5 parameter settings for OLTP/BW

Note 337445 - liveCache and memory management

Note 487972 - Operating system parameterization of liveCache

Note 941735 - SAP memory management for 64-bit Linux systems

There does not seem to be any Redhat specific tuning settings (though a couple of Suse recommendations), except for a general mention of all Linux systems with this direct I/O suggestion:

"As of Linux Version 2.6, we recommend that you set the parameter to the value YES rather than DEFAULT NO.

Further notes on this topic:

Note 977515:. Linux System paged during MaxDB data backup/add volume"

The parameters I am wanting to tune are in /etc/sysctl.conf, so since there does not seem to be any Livecache specific parameters, I was going to just take the general recommendations from Note 941735 - SAP memory management for 64-bit Linux systems and set our parameters as follows:

- kernel.shmall

As a configuration recommendation, kernel. shmall can be configured as the amount of virtual memory in the Linux system (RAM + Swap).

- kernel.shmmax

This kernel parameter specifies how large an individual SysV Shared Memory Segment is allowed to be. In the case of an STD implementation, the parameter must be set sufficiently large in order to allow em/initial_size_MB. The value is specified in the unit Bytes so that "21474836480", for example, permits segments of 20 GB.

I am thinking to tune kernel.shmall to 90% of RAM+swap, and kernel.shmmax to 90% of RAM. Also will be setting the following parameters as well:

kernel.msgmni=1024

kernel.sem=1250 256000 100 1024

1. Parameter kernel.sem corresponds to "semmsl semmns semopm semmni"

vm.max_map_count=1000000

Does anyone out there have any different experiences or tips on how they set these up, specific to Livecache? The SAP application tuning is pretty straightforward, but wanted to make sure we didn't overlook anything with Livecache.

Thanks,

Derek

[markus_doehr2 · Accepted solution]

> - kernel.shmall

> - kernel.shmmax

> kernel.msgmni=1024

> kernel.sem=1250 256000 100 1024

Those are all upper limits so you can increase them higher without impacting the system stability.

> vm.max_map_count=1000000

This is just for an application server using the mmap() (es/implementation=map) memory model.

We also add

net.core.rmem_max=8388608
net.core.wmem_max=8388608
net.core.wmem_default=8388608
net.core.rmem_default=8388608
net.core.netdev_max_backlog=4096

so that the network uses bigger "window" (mainly for speeding up the backup over the network).

Markus

[former_member184709 · Accepted solution]

Markus,

Thank you very much for the response, that was really helpful!