[Koha-bugs] [Bug 13431] Shared FastMmap file causes issues

[bugzilla-daemon at bugs.koha-community.org]

http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=13431

--- Comment #11 from Jacek Ablewicz <abl at biblos.pk.edu.pl> ---
(In reply to Tomás Cohen Arazi from comment #9)
> I guess for most of the cases mysql does a better job caching query results.

It looks that way - fastmmap turns out to be not all that fast after all ;). I
did some simple tests (fetching BKS framework with GetMarcStructure() 1000
times in the row):

- not using Koha::Cache, mysql query cache enabled: 27 seconds
- not using Koha::Cache, mysql query cache disabled: 39s
- fastmmap_cache: 35s (!)
- memory_cache: 10s

However, such test case is pretty artificial - things may be different for
syspref caching, authorized values caching, how would it behave on heavily
loaded servers, what kind of impact from connection latencies we may expect if
persistent caching is not in use and mysql is on the different machine (I guess
quite a big impact regarding sysprefs and AVs fetching?) etc.

On the other hand, I wonder how many people in the wild may be actually using
CACHING_SYSTEM=fastmmap_cache (or are even aware of such possibility)?
Interesting thing about fastmmap_cache is that it is currently never used by
default nor as a fallback mechanism (at least not since Bug 12041). But it
still gets loaded and initialized each and every time, causing possible
"Permision denied ..." issues even on such setups which do not use fastmmap
cache at all.

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