[Linux-cluster] Slowness above 500 RRDs

[Wagner Ferenc]

Ferenc Wagner <wferi at niif.hu> writes:

> There's a good bunch of RRDs in a directory.  A script scans them for
> their last modification times, and then updates each in turn for a
> couple of times.  The number of files scanned and the length of the
> update rounds are printed.  The results are much different for 500 and
> 501 files:
>
> filecount=501
>   iteration=0 elapsed time=10.425568 s
>   iteration=1 elapsed time= 9.766178 s
>   iteration=2 elapsed time=20.14514 s
>   iteration=3 elapsed time= 2.991397 s
>   iteration=4 elapsed time=20.496422 s
> total elapsed time=63.824705 s
>
> filecount=500
>   iteration=0 elapsed time=6.560811 s
>   iteration=1 elapsed time=0.229375 s
>   iteration=2 elapsed time=0.202973 s
>   iteration=3 elapsed time=0.203439 s
>   iteration=4 elapsed time=0.203095 s
> total elapsed time=7.399693 s

Following up to myself with one more data point: raising
SHRINK_CACHE_MAX from 1000 to 20000 in gfs/dlm/lock_dlm.h helps
significantly, but still isn't enough.  Besides, I don't know what I'm
doing.  Should I tweak the surrounding #defines, too?

I'd be grateful for any advice.
-- 
Thanks,
Feri.