Comment 26 for bug 635834

We are tuning different aspectsof I/O perfomance.

E.g. Create a /var/lib/rpm/DB_CONFIG file with these 2 lines:
    set_cachesize 0 67108864 4
    set_mp_mmapsize 268435456
1st line permits 4 cache files of 64Mb
2nd line pemits up to 256Mb to be memory mapped.

Prime the cache by running as root

    rpm -qa

Show cache hits by doing
    cd /var/lib/rpm
    /usr/lib/rpm/db_stat -m

Adding -Z will rezero the counters.

The above is a rather different I/O trace than you have reported with strace.

Yes, O_DIRECT with Berkeley DB likely knows better than the kernel ;-)

And "quick hacks" tend to get forgotten. You have no idea how many "quick hacks"
there are in RPM that noone has a clue about.

I have no problem whatsoever using available I/O performance in a linux
kernel. But tuning a database != a tuna fish.