System information

182 System Analysis and Tuning Guide
15.1.7.2 Directory Entry Cache
This is an in-memory cache of the directory entries in the system. These contain a
name (the name of a file), the inode which it refers to, and children entries. This
cache is used when traversing the directory structure and accessing a file by name.
15.2 Reducing Memory Usage
15.2.1 Reducing malloc (Anonymous)
Usage
Applications running on SUSE Linux Enterprise Server 11 SP3 can allocate more
memory compared to SUSE Linux Enterprise Server 10. This is due to glibc
changing its default behavior while allocating userspace memory. Please see
http://www.gnu.org/s/libc/manual/html_node/Malloc-Tun
able-Parameters.html for explanation of these parameters.
To restore a SUSE Linux Enterprise Server 10-like behavior,
M_MMAP_THRESHOLD should be set to 128*1024. This can be done with mal-
lopt() call from the application, or via setting MALLOC_MMAP_THRESHOLD en-
vironment variable before running the application.
15.2.2 Reducing Kernel Memory
Overheads
Kernel memory that is reclaimable (caches, described above) will be trimmed auto-
matically during memory shortages. Most other kernel memory cannot be easily re-
duced but is a property of the workload given to the kernel.
Reducing the requirements of the userspace workload will reduce the kernel memory
usage (fewer processes, fewer open files and sockets, etc.)