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Michael Cahill
*nix forums Guru Wannabe
Joined: 26 May 2005
Posts: 219
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 Posted: Wed Apr 13, 2005 12:46 am Post subject:
Re: Large cache size support
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| Quote: | Here is my problem:
I'm unable to get BDB to use a cache size greater than 1GB
866983779
bytes and to get it to use the 1.8GB I had to split it across 59
cache
files! What gives? Is this a BDB problem or a Linux problem or Java
problem or what? The upper limit on 32bit is supposed to be 4GB. I'm
barely getting a third of that. Does anyone have a clue?
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To configure a single cache region of 1.8GB, you'll need to have that
much free virtual memory in one contiguous block. What's happening is
that the JVM and shared libraries reserve blocks of memory in ways that
leave you without one big block.
In addition, the operating system will reserve part of the address
space (1GB by default, with Linux 2.6), so that makes your upper limit
3GB, not 4. There are patches to the kernel that address this, but
they incur runtime overhead. See this article:
http://kerneltrap.org/node/2450
for more information.
Of course, the simplest way to configure a larger cache is to run on a
64-bit CPU.
You should also find that reducing the size of the Java heap (with the
"-Xmx" command line flag) allows you to configure a larger cache, but
there is obviously a tradeoff there with the corresponding increase in
garbage collection.
In any case, you're getting 60% of the maximum now -- it may be
possible to do better, but not by a whole lot if you want to have a JVM
in the same address space.
Regards,
Michael. |
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studdugie@gmail.com
*nix forums beginner
Joined: 21 Jun 2005
Posts: 28
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| Posted: Tue Apr 12, 2005 7:06 pm Post subject:
Large cache size support
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Here is my setup:
BDB: BerkeleDB 4.3.27NC (3 patches)
Arch: Intel Xeon 3.06GHz
RAM: 6GB
OS: Gentoo Linux 2.6.11.5
glibc: Compiled by GNU CC version 3.3.5 (Gentoo Linux 3.3.5-r1,
ssp-3.3.2-3, pie-8.7.7.1).
Compiled on a Linux 2.6.8 system on 2005-02-26.
Available extensions:
GNU libio by Per Bothner
crypt add-on version 2.1 by Michael Glad and others
Native POSIX Threads Library by Ulrich Drepper et al
BIND-8.2.3-T5B
NIS(YP)/NIS+ NSS modules 0.19 by Thorsten Kukuk
Thread-local storage support included.
gcc: 3.3.5
Language: J2SE 1.5.0_02
FS: XFS
Here is my problem:
I'm unable to get BDB to use a cache size greater than 1GB 866983779
bytes and to get it to use the 1.8GB I had to split it across 59 cache
files! What gives? Is this a BDB problem or a Linux problem or Java
problem or what? The upper limit on 32bit is supposed to be 4GB. I'm
barely getting a third of that. Does anyone have a clue? |
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