v2.6 performance slowdown on MPC8xx: Measuring TLB cache misses
wd at denx.de
Mon Apr 25 06:59:40 EST 2005
thanks for starting this discussion, and for providing a patch for 8xx.
However, I think we should not only look at the TLB handling problems
on the 8xx processors. This is probably just a part of the problem.
In general the 2.6 performance on (small) embedded systems is much,
much worse than what we see with a 2.4 kernel.
I put some results (2.4.25 vs. 220.127.116.11 on a MPC860 and on a MPC8240)
Here is the summary:
Using the 2.6 kernel on embedded systems implicates the following
* Slow to build: 2.6 takes 30...40% longer to compile
* Big memory footprint in flash: the 2.6 compressed kernel image is
* Big memory footprint in RAM: the 2.6 kernel needs 30...40% more
RAM; the available RAM size for applications is 700kB smaller
* Slow to boot: 2.6 takes 5...15% longer to boot into multi-user mode
* Slow to run: context switches up to 96% slower, local communication
latencies up to 80% slower, file system latencies up to 76% slower,
local communication bandwidth less than 50% in some cases.
It's a disappointing result, indeed.
Software Engineering: Embedded and Realtime Systems, Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Another megabytes the dust.
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