summary Re: memory problems

From: Jieming Zhu (
Date: Thu Sep 15 1994 - 08:47:20 CDT

Original question:

> We have 786M memory on our Solbourne Series6 server running Solbourne
> OS/MP 4.1B (equivalent of SUN OS 4.1.2). Recently, the vmstat
> constantly showed that the free memory is only about 70M. Yet, I
> counted the total memory used by all processes is about 530M. Where
> did the other 200M something go? Can the OS take that much memory?


Most answers pointed out the uncounted memory could be used by kernel. noted that 10% of the RAM will be
allocated by the kernel for Caching Disk Accesses. Another manager
(Sorry, I deleted your mail reply and couldn't remember your name)
noted buffer cache could use a lot memory as well.
suggested shared memory. The most detailed answer came from and I quote here:

  The memory is used as disk buffer cache by the OS. The disk cache
  competes with user programs for free memory from the pool of unused
  pages. When a process needs memory it will be allocated by freeing
  pages of memory ona least recently used basis. This dynamic allocation
  is in contrast to the System V way where you allocated a fixed portion
  of your memory as disk buffer cache.

  The bottom line is don't worry too much about it. The other thing is
  that if you add up the RES coilumn of ps that includes memory allocated
  to shared libraries, even though a lot of the time those pages will be
  shared by many processes, so it is likely that a lot less than 530M is
  really being used by user processes.

Thanks to:
Tow more replies. (unfortunately, I deleted your mails. My
gratefulness to your contributions as well.)

Jieming Zhu			   |VoiceMail: (316)636-8649
Microelectronic Products Division  |Email:
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