Arjan van de Ven wrote:
On Wed, 05 Dec 2007 21:15:30 +0100
Holger Wolf <[email protected]> wrote:
We discovered performance degradation with dbench when using kernel
2.6.23 compared to kernel 2.6.22.
In our case we booted a Linux in a IBM System z9 LPAR with 256MB of
ram with 4 CPU's. This system uses a striped LV with 16 disks on a
Storage Server connected via 8 4GBit links.
A dbench was started on that system performing I/O operations on the
striped LV. dbench runs were performed with 1 to 62 processes.
Measurements with a 2.6.22 kernel were compared to measurements with
a 2.6.23 kernel. We saw a throughput degradation from 7.2 to 23.4
this is good news!
dbench rewards unfair behavior... so higher dbench usually means a
worse kernel ;)
tests with 2.6.22 including CFS show the same results.
This means the pressure on page cache is much higher when all processes
run in parallel.
We see this behavior as well with iozone when writing on many disks with
many threads and just 256 MB memory.
This means the scheduler schedules as it should - fair.
regards Holger
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