Comment 39 for bug 635834

(In reply to comment #37)
> One last note ...
>
> db_stat -m claims 80M for cache, you claim 100M for Packages.
>
> And your cache hits are ~60%, not 100%.
>
> Increasing cache to accomodate workset would seem to be useful.

Well - sure there is no problem to increase the case size - the question is - how to make it efficiently (and again - why the RPM user should actually care about DB cache size - at least man page for RPM hides DB_CONFIG from the users like me ;)

Let's get back to increasing the the case size doesn't improve initial problem - and IMHO makes later cached processing actually slower - though in range of couple milliseconds - but it is measurable and consistent across multiple measurements.

I admit the time for --nodigest --nosignature goes down to 10 seconds for uncached __db* case - but let me repeat that wallclock experiment from comment 1 clearly shows that, that using even cachesize 0 and doing cat Packages; followed by rpm command outperforms this solution by large factor.

IMHO keypoint is to enable full mmap usage preferable with MAP_POPULATE if available and I'm getting the feeling that I'll need to look on this myself... :(

As for degradation BDB - if my simple case is not the sign of degradation (i.e. DB size growth by 30% and its getting slower by approximately same factor) then of course there is no problem to care about ;)