IT Management

echo 0 > /sys/bus/ap/poll_thread

To check the current status of the polling thread, enter:

cat /sys/bus/ap/poll_thread

1 – means enabled

0 – means disabled

The measurement environment used for this article was an IBM System z9 (2094-S18) configured with:

• An LPAR with four logical processors

• IBM System Storage DS8300 (2107- 922)

• One Crypto Express2 (CEX2) feature

• SLES10 SP1, including Linux generic zcrypt device driver 2.1.0, OpenSSL 0.9.8a, Interface Library (libICA) 1.3.7, and OpenSSL HW engine support ibmca 1.3.7.


Important data that’s exchanged over an open, insecure network should be protected to save the company assets. Encryption algorithms or protocols are available for that purpose. The SSL protocol was designed to secure a connection over an open network. However, cryptographic algorithms are CPU-intensive. This can possibly result in poor application performance, the stronger the encryption algorithm is.

Additional cryptographic hardware is recommended to provide acceptable performance for a secured system such as a secure Web server. Ensure that your Linux and LPAR application configuration setup can use the CPACF and CEX2 hardware. Usually, this requires correct settings in the application configuration files and doesn’t work out of the box.

More Information

To learn more, refer to IBM documentation, including Linux on System z Device Drivers, Features, and Commands (SC33-8411-00). You can access these and other resources at More performance-related information regarding Linux on System z is accessible at


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