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• buffermem — Allows you to control the percentage amount of total system memory to be used
for buffer memory. Typical output for this file looks like this:
2
The first and last values set the minimum and maximum percentage of memory to be used as buffer
memory, respectively. The middle value sets the percentage of system memory dedicated to buffer
memory where the memory management subsystem will begin to clear buffer cache more than
other kinds of memory to compensate for a general lack of free memory.
• freepages — Displays various values related to free pages of system memory. This file looks
similar to this:
223 446 669
The first value shows the minimum number of free pages permitted before the kernel takes over
control of allocating additional memory. The second value gives the number of free pages before
the kernel begins swapping aggressively to preserve performance. The third value is the number
of free pages that the system attempts to keep available at all times.
• kswapd — Sets various values concerned with the kernel swap-out daemon, kswapd. This file
has three values:
512 32 8
The first value sets the maximum number of pages that kswapd will attempt to free in a single
attempt. The larger this number, the more aggressively the kernel can move to free pages. The
second value sets the minimum number of times that kswapd attempts to free a page. The third
value sets the number of pages kswapd attempts to write in a single attempt. Proper tuning of this
final value can improve performance on a system using a lot of swap space by telling the kernel to
write pages in large chunks, minimizing the number of disk seeks.
• max_map_count — Configures the maximum number of memory map areas a process may
have. In most cases, the default value of 65536 is appropriate.
• overcommit_memory — Contains a value that, when set to something other than the default
of 0, allows the kernel to skip a standard check to see if there is enough memory before allocating
it.
• pagecache — Controls the amount of memory used by the page cache. The values in page-
cache are percentages, and they work in a similar way as buffermem to enforce minimums
and maximums of available page cache memory.
• page-cluster — Sets the number of pages read in a single attempt. The default value of 4,
which actually relates to 16 pages, is appropriate for most systems.
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Chapter 4:The /proc Filesystem