… to be understand is – cache hit ratio can be computed differently for different engines. For example for Innodb page hits are counted for all… and you have 100 rows per page you will get 1 miss per page and 99 hits, making your hit ratio 99% for what would be 0% in many peoples mind. But what is even more important is hit ratio…
Post: MySQL Query Cache
July 27, 2006 By 69 Comments
… rows now can be instantly summoned from query cache. It also means query has to be exactly the same and deterministic, so hit… bad. With other caches you may implement version based or timeout based invalidation which can offer much better hit ratio for certain application. It is not that fast Query Cache is fast compared to running…
Post: Predicting Performance improvements from memory increase
August 7, 2008 By 6 Comments
… we predict the benefit from increasing the memory and so cache sizes ? I typically start by looking at the type of… for locking. Consider for example bunch of transactions updating single row in the table. Having such workload you would likely see… estimations and take IO subsystem into account – even with same cache hit ratio more data and more load means there are higher demands…
Post: How simple answer are you looking for ?
April 11, 2007 By 5 Comments
… be helpful – there are workloads when even with 1% matching rows you’re better of doing full table scans, and there… Compared to Your Database Size Should you Have” , “What Key Cache Hit Ratio is Good One” This often gives me head aches – I…
Post: SHOW INNODB STATUS walk through
July 17, 2006 By 40 Comments
… writes are done to OS cache, and being sequential writes these …hit ratio which measures buffer pool efficiency. 1000/1000 corresponds to 100% hit rate. It is hard to tell what buffer pool hit…IO bound workload with hit rate of 995/1000. ————– ROW OPERATIONS ————– 0 queries inside…
Post: Living with backups
November 6, 2008 By 28 Comments
… significantly degraded performance. Anything else? All modern systems usually use caching of whatever is being read from a storage. It allows… random “garbage” for no good reason. Since the hit ratio becomes worse as the cache is being filled with random information additional I… GLOBAL STATUS LIKE “Threads_connected”‘); … if ($$row[1] < 10) { $is_running= 1; } if ($$row[1] > 50) { $is_running= 0; } … $kid…
Comment: Using MyISAM in production
June 19, 2006 By 35 Comments
… have any long running selects you can get stuck. The row cache problem is actually partialy solved by using MMAP in MySQL… but you still can’t configure its size or measure hit ratio. If you’re on Solaris “dtrace” is probably something you…
Post: Shard-Query EC2 images available
May 11, 2011 By 2 Comments
…. row *************************** Name: ontime_fact Engine: InnoDB Version: 10 Row_format: Compact Rows: 6697533 Avg_row_… gets over 16:1 compression ratio(compared to Innodb, 8:…”. Now, in the EC2 console hit CTRL-A to select …links table-definition-cache=16384 table-open-cache=128 thread-cache-size=…
Post: On Good Instrumentation
May 31, 2010 By 1 Comment
…t say why it has taken so long. Was it row level lock ? waiting on disk IO or was it simply…on response I’d like to know if it was hit, miss or error. The way I use it may be…high miss ratio. Checking what is going on with memcache01 shows it just was restarted (and hence has almost empty cache). This…
