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Navneet Kumar

MySQL AB :: High Performance MySQL Chapter 6: Server Performance Tuning - 0 views

dev.mysql.com/...ch06.html

mysql optinization performance tuning

shared by Navneet Kumar on 07 Sep 07 - Cached
  • Navneet Kumar on 07 Sep 07
     
    performance tuning for high performnace mysql
Navneet Kumar

Synchronization and the Java Memory Model - 3 views

gee.cs.oswego.edu/jmm.html

Java JVM Synchronization Concurrency MemoryModel Threads

shared by Navneet Kumar on 08 Apr 11 - Cached
    • Navneet Kumar
      Navneet Kumar on 08 Apr 11
       
      Assignment to a long, double, float variables are not Atomic.
  • as-if-serial property of these manipulations shields sequential programmers from needing to know if or how they take place. Programmers who never create their own threads are almost never impacted by these issues
  • All changes made in one synchronized method or block are atomic and visible with respect to other synchronized methods and blocks employing the same lock, and processing of synchronized methods or blocks within any given thread is in program-specified order. Even though processing of statements within blocks may be out of order, this cannot matter to other threads employing synchronization.
  • ...6 more annotations...
  • atomicity alone does not guarantee that you will get the value most recently written by any thread. For this reason, atomicity guarantees per se normally have little impact on concurrent program design
  • Thread.start has the same memory effects as a lock release by the thread calling start, followed by a lock acquire by the started thread
  • releasing a lock forces a flush of all writes from working memory employed by the thread, and acquiring a lock forces a (re)load of the values of accessible fields. While lock actions provide exclusion only for the operations performed within a synchronized method or block, these memory effects are defined to cover all fields used by the thread performing the action.
  • If a field is declared as volatile, any value written to it is flushed and made visible by the writer thread before the writer thread performs any further memory operation (i.e., for the purposes at hand it is flushed immediately). Reader threads must reload the values of volatile fields upon each access.
  • you will obtain either its initial value or some value that was written by some thread, but not some jumble of bits resulting from two or more threads both trying to write values at the same time
  • As a thread terminates, all written variables are flushed to main memory.
Navneet Kumar

MySQL Performance Blog » What to tune in MySQL Server after installation - 0 views

www.mysqlperformanceblog.com/...ysql-server-after-installation

mysql optimization performance tuning

shared by Navneet Kumar on 25 Sep 07 - Cached
  • Navneet Kumar on 25 Sep 07
     
    tuning mysql server for perfornmance
Navneet Kumar

MySQL Performance Blog » MySQL Query Cache - 0 views

www.mysqlperformanceblog.com/...mysql-query-cache

caching mysql performance tuning

shared by Navneet Kumar on 26 Sep 07 - Cached
  • It does not cache the plan but full result sets
  • so it looks at first letter of the query and if it is “S” it proceeds with query lookup in cache if not - skips it.
  • Might not work with transactions
  • ...15 more annotations...
  • uses non-deterministic functions such as UUID(), RAND(), CONNECTION_ID() etc it will not be cached.
  • If table gets modification all queries derived from this table are invalidated at once
  • if you have high write application such as forums, query cache efficiency might be pretty low due to this.
  • all queries are removed from cache on table modifications - if there are a lot of queries being cached this might reduce update speed a bit
  • Qcache_free_memory and Qcache_lowmem_prunes
  • number of your selects - Com_select and see how many of them are cached. Query Cache efficiency would be Qcache_hits/(Com_select+Qcache_hits).
  • One portion of query cache overhead is of course inserts so you can see how much of inserted queries are used: Qcache_hits/Qcache_inserts Other portion of overhead comes from modification statements which you can calculate by (Com_insert+Com_delete+Com_update+Com_replace)/Qcache_hits
  • want to set query cache
  • means it is much more efficient as query which required processing millions of rows now can be instantly summoned from query cache
  • It also means query has to be exactly the same and deterministic, so hit rate would generally be less
  • full page caching
  • not using query_cache_wlock_invalidate=ON locking table for write would not invalidate query cache so you can get results evenif table is locked and is being prepared to be updated
  • it can serve responses very fast doing no extra conversion or processing.
  • but it is still not as fast as specially designed systems such as memcached or local shared memory.
  • It is not distributed If you have 10 slaves and use query cache on all of them cache content will likely be the same, so you have multiple copies of the same data in cache effectively wasting memory
  • Navneet Kumar on 26 Sep 07
     
    mysql query caching
Navneet Kumar

mysql query cache - 0 views

jayant7k.blogspot.com/...mysql-query-cache.html

mysql performance tuning

shared by Navneet Kumar on 26 Sep 07 - Cached
  • Navneet Kumar on 26 Sep 07
     
    tuning mysql performance with query caching
Navneet Kumar

Table types in MySQL: Part 1 - HEAP tables - 0 views

www.databasejournal.com/...3077531

heap_tables mysql performance

shared by Navneet Kumar on 03 Sep 07 - Cached
  • Navneet Kumar on 03 Sep 07
     
    Heap tables : in-memory tables
Navneet Kumar

When Not to Normalize your SQL Database - SWiK - 0 views

swik.net/...bjdmc

database database_design normalization

shared by Navneet Kumar on 28 Aug 07 - Cached
  • With the above design, it takes six SQL Join operations to access and display the information about a single user. This makes rendering the profile page a fairly database intensive operation which is compounded by the fact that profile pages are the most popular pages on social networking sites.
  • Database denormalization is the kind of performance optimization that should be carried out as a last resort after trying things like creating database indexes, using SQL views and implementing application specific in-memory caching. However if you hit massive scale and are dealing with millions of queries a day across hundreds of millions to billions of records or have decided to go with database partitioning/sharding then you will likely end up resorting to denormalization
    • Navneet Kumar
      Navneet Kumar on 28 Aug 07
       
      De-Normalization is OK if you are'nt going to update
  • Denormalization means that you you are now likely to deal with data inconsistencies because you are storing redundant copies of data and may not be able to update all copies of a column value simultaneously  when it is changed for a variety of reasons. Having tools in your infrastructure to support fixing up data of this sort then become very important.
  • Navneet Kumar on 28 Aug 07
     
    De-normalizing database to improve speed.
Navneet Kumar

Tuning a MySQL server in 5 minutes - 0 views

rudd-o.com/...ng-a-mysql-server-in-5-minutes

mysql performance tuning

shared by Navneet Kumar on 07 Sep 07 - Cached
  • Navneet Kumar on 07 Sep 07
     
    max_connections  max_user_connections table_cache
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