03-11-2015
Quote:
Originally Posted by
umen
...
how do i decrease virtual size of a process in c++/c ?
thanks
You basically need to explicitly control all memory allocation, using library calls like mmap() and munmap().
As you've found, malloc_trim() doesn't really work, because any one malloc()'d bit of memory in the wrong location in the heap will wind up pinning the entire heap anyway. That's because of the way the brk()/sbrk() calls underlying malloc()/free() work in managing the heap - the standard implementation heap of memory using brk()/sbrk() has to be a single contiguous chunk of memory that has a fixed starting point. If there is any memory in use that's deep into the allocated heap space, all the memory up to and including that in use memory can't be returned to the OS.
If this is for work, instead of spending time and money trying to solve this problem by writing what will probably be a lot of buggy code that doesn't really solve anything, just buy more RAM for you server.
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LEARN ABOUT MOJAVE
libcache
libcache(3) BSD Library Functions Manual libcache(3)
NAME
libcache -- the caching framework
SYNOPSIS
#include <cache.h>
DESCRIPTION
The libcache framework provides a facility for creating in memory data caches. Each cache is a mutable dictionary that associates values
with their keys. A cache limits the number of values it keeps according to available system memory and selects values to evict when the
limit is exceeded. Recently and frequently used values are less likely to be selected for eviction.
Cache keys and values should be cast as pointers. The framework provides a callback interface for supporting arbitrary types of keys and
values and implements callback functions for common types. See cache_callbacks(3) for more information.
Clients retrieve a value previously added to a cache using the value's key. When the client gets a value, the cache increments a reference
count on the value. When the client finishes with a value retrieved from a cache they must release the value back to the cache. Referenced
values are considered in use and will not be evicted. The cache may evict unreferenced values (e.g. to make room for other values or reduce
its size).
The number of values allowed in a cache at one time is managed by the cache framework. Cache size will grow when the system has available
memory and shrink under memory pressure.
Libcache is thread-safe. It is not safe to call back into the cache API from cache callback functions.
SEE ALSO
cache_create(3), cache_set_and_retain(3)
Darwin May 7, 2009 Darwin