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Date:      Sun, 28 Jan 2001 11:36:40 +0200
From:      "Kobi Luz" <kobi@cwnt.com>
To:        <freebsd-questions@freebsd.org>
Subject:   regarding use of mmap against brk in malloc
Message-ID:  <001501c0890d$d1e65fd0$db00a8c0@KOBI>

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Hi.

The current implementation of malloc, uses brk() and sbrk() to allocate new
pages
from the OS. As the allocated pages are successive, pages are returned to
the
OS only when the last page is free, which often does not happen. This
creates
a situation where almost no memory is returned to the OS even after being
freed
by the process. We want to use calls to mmap() instead of brk() to address
this
problem.
Is there any reasons we should know about why we should not use only calls
to mmap(), and not use calls to brk() at all in the implementation of
malloc?
Are there any advantages for brk() over mmap() (like performance issues)
that
we should know about, or any problems with the use of mmap() in malloc?

Thanks a lot,
Kobi Luz.




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