/dev/zero performance drop between SLE10 SP1 and SP2
This document (7002112) is provided subject to the disclaimer at the end of this document.
SUSE Linux Enterprise Desktop 10 SP2
A SUSE Linux Enterprise 10 system was updated from Support Pack 1 to Support Pack 2.
- The read/write performance of /dev/zero as measured e.g. by
time dd if=/dev/zero of=/dev/null bs=1G count=1has dropped significantly.
- I/O performance as reported by benchmark software has dropped significantly.
/dev/zero is a special character device file. When data is written to it, it is discarded, i.e. it operates as a "bit bucket". When data is read from it, it produces a stream of bytes of value zero.
Prior to Service Pack 2, the kernel had a special mechanism, called "ZERO_PAGE", which was used to implement /dev/zero. In Service Pack 2's kernel, this mechanism has been removed as on larger systems, it could cause livelocks (a form of resource starvation). The reduced performance of /dev/zero is a side effect of this removal.
This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.
- Document ID:7002112
- Creation Date: 08-Dec-2008
- Modified Date:10-Mar-2021
- SUSE Linux Enterprise Desktop
- SUSE Linux Enterprise Server
For questions or concerns with the SUSE Knowledgebase please contact: firstname.lastname@example.org