Re: blk_congestion_wait racy?

[Martin Schwidefsky]

> Martin, have you tried adding this printk?

Sorry for the delay. I had to get 2.6.4-mm1 working before doing the
"ouch" test. The new pte_to_pgprot/pgoff_prot_to_pte stuff wasn't easy.
I tested 2.6.4-mm1 with the blk_run_queues move and the ouch printk.
The first interesting observation is that 2.6.4-mm1 behaves MUCH better
then 2.6.4:

2.6.4-mm1 with 1 cpu
# time ./mempig 600
Count (1Meg blocks) = 600
600  of 600
Done.

real    0m2.587s
user    0m0.100s
sys     0m0.730s
#

2.6.4-mm1 with 2 cpus
# time ./mempig 600
Count (1Meg blocks) = 600
600  of 600
Done.

real    0m10.313s
user    0m0.160s
sys     0m0.780s
#

2.6.4 takes > 1min for the test with 2 cpus.

The second observation is that I get only a few "ouch" messages. They
all come from the blk_congestion_wait in try_to_free_pages, as expected.
What I did not expect is that I only got 9 "ouches" for the run with
2 cpus.

blue skies,
   Martin

Linux/390 Design & Development, IBM Deutschland Entwicklung GmbH
Schönaicherstr. 220, D-71032 Böblingen, Telefon: 49 - (0)7031 - 16-2247
E-Mail: schwidefsky@xxxxxxxxxx


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