Memcached Release Candidate 1.4.2-rc1
dormando
PLEASE MAKE LOTS OF TESTING!
http://code.google.com/p/memcached/wiki/ReleaseNotes142rc1
This release comes again with many bugfixes, and a small number of useful
features, described briefly in the release notes above. 1.4.2 final will
be up in 2-3 days, based on response to testing. We feel that this release
is of high quality.
Linux hugetlbfs support is cool (eek a few % more speed out of memory
accesses). The new evictions_nonzero per-slab counter is also cool, as you
now have a seperate counter for evictions that had an explicit expiration
time.
However, this release comes with a loaded handgun. Please do not point it
at your feet. Or put it in your mouth. Or point it at your friends.
The [in]famous 1MB item size limit is now a start time tunable (-I)
As described in the release notes, it accepts a few formats:
-I 2048
^ bytes
-I 128k
^ kilobytes
-I 2m
^ megabytes
This doesn't *just* raise the item limit. What this actually does is raise
the size of the slab page. Previously, the slabber works like:
"Hello! I need 50 bytes of memory for this fancy value I have here."
"Okay, have a chunk from slab 1. Oh, but there's no RAM here. Hold on I'll
grab a page and butcher it."
... Then it fetches a 1MB page, then cuts it up into 10,000 little pieces,
and hands back the caller a small chunk.
If you set -I 64m, however.
"Hello! I need 50 bytes of memory for this fancy value I have here."
"Hold on let me get the truck. Also the chainsaw."
So before you abuse this value in the *upwards* direction, you should give
it some serious thought. On that note, it is useful to limit the maximum
item size to be smaller than a megabyte.
I'll be beating up the FAQ over the next few days for the next round of
usual clarifications. Hopefully we can keep this all clear ;)
-Dormando