Re: IA64 Linux VM performance woes

From: Marcelo Tosatti
Date: Wed Apr 21 2004 - 16:00:57 EST

On Wed, Apr 21, 2004 at 09:39:23PM +0900, Satoshi Oshima wrote:
> Hello, Michael and all.
> We have realized the same kind of performance issue.
> In our case it is not an IA64 huge scale system but an IA32
> server system.
> In our experiment, we see file I/O throughput decline on
> the server with over 8GByte memory. Kernel versions we use
> are 2.6.0 and Red Hat AS3. We show our experiment.
> Below is our hardware configuration and test bench.
> CPUs: Xeon 1.6Ghz - 4way
> Memory: 12GB
> Storage: ATA 120GB
> File I/O workload generator consists of 1024 processes and
> generates 100KByte to 5MByte file write. Using "mem=" option,
> we change the memory recognition 2GByte to 12GB.
> Below is the result ( unit: MByte/sec).
> 2GB 4GB 8GB 12GB
> 2.6.0 13.1 18.5 18.4 16.1
> AS3 11.0 11.3 10.3 8.92
> The result shows throughput decline occurs when the server
> has over 8GByte memory.

Can you share the tests with us? It would be great.

> We agree that your proposal is good idea. It reduces cache
> memory reclaiming cost to set upper bound on number of
> cache memory pages.

I'm not exactly sure of the problem (others (Andrea, Andrew, etc) probably are). Still,
one useful thing would be to rerun the benchmarks on recent kernels (2.6.6-rc2, which contains a
lot of VM rewrite and tuning). It will be interesting to know the results.

> Generally it is very difficult to build one system which
> could handle various type of workloads well. So we hope
> Linux would have kernel parameter tuning interface.
> We would be very happy if we could share information to
> manage large scale memory.
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