I worked with application recently which has great memcached hit ratio – over 99% but yet still has average page response time over 500ms. Reason ? There are hundreds memcached gets and even though they have some 0.4ms response time they add up to add hundreds of ms to the total response time.
FlashCache: more benchmarks
May 18, 2010 By 15 Comments
Previously I covered simple case with FlashCache, when data fits into cache partitions, now I am trying to test when data is bigger than cache. But before test setup let me address some concern (which I also had). Intel X25-M has a write cache which is not battery backuped, so there is suspect you may [...]
Why you should ignore MySQL’s key cache hit ratio
February 28, 2010 By 28 Comments
I have not caused a fist fight in a while, so it’s time to take off the gloves. I claim that somewhere around of 99% of advice about tuning MySQL’s key cache hit ratio is wrong, even when you hear it from experts. There are two major problems with the key buffer hit ratio, and [...]
Active Cache for MySQL
January 10, 2010 By 11 Comments
One of the problems I have with Memcache is this cache is passive, this means it only stores cached data. This means application using Memcache has to has to special logic to handle misses from the cache, being careful updating the cache – you may have multiple data modifications happening at the same time. Finally [...]
More on table_cache
November 26, 2009 By 7 Comments
In my previous post I looked into how large table_cache actually can decrease performance. The “miss” path is getting more expensive very quickly as table cache growths so if you’re going to have high miss ratio anyway you’re better off with small table cache. What I have not checked though is how does table_cache (or [...]
How innodb_open_files affects performance
November 18, 2009 By 4 Comments
Recently I looked at table_cache sizing which showed larger table cache does not always provides the best performance. So I decided to look at yet another similar variable – innodb_open_files which defines how many files Innodb will keep open while working in innodb_file_per_table mode. Unlike MyISAM Innodb does not have to keep open file descriptor [...]
table_cache negative scalability
November 16, 2009 By 23 Comments
Couple of months ago there was a post by FreshBooks on getting great performance improvements by lowering table_cache variable. So I decided to investigate what is really happening here. The “common sense” approach to tuning caches is to get them as large as you can if you have enough resources (such as memory). With MySQL [...]
Getting annoyed with MyISAM multiple key caches.
May 1, 2009 By 11 Comments
As I’ve wrote few times using multiple key caches is a great way to get CPU scalability if you’re using MyISAM. It is however very annoying – this feature really looks half baked to me. The problem with multiple key caches and mapping of tables to the different files is – there is no way [...]
A quick way to get memcached status
November 26, 2008 By 3 Comments
There are all sorts of different interfaces to memcached, but you don’t need any of them to make requests from the command line, because its protocol is so simple. Try this, assuming it’s running on the usual port on the local machine:
Heikki Tuuri answers to Innodb questions, Part II
November 4, 2007 By 13 Comments
I now got answers to the second portions of the questions you asked Heikki. If you have not seen the first part it can be found here. Same as during last time I will provide my comments for some of the answers under PZ and will use HT for original Heikkis answer. Q26: You also [...]
