As you know MyISAM does not cache data, only indexes. MyISAM assumes OS cache is good enough and uses pread/pwrite system calls… can be enabled by –myisam_use_mmap=1 startup option. In this case instead of systems call MyISAM will use memcpy function. There is a memory addressing limit for 32bit platforms – 2Gb, so the datafiles over 2GB will be used…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…_mmap_sizeblogpercona.commanual myisam_recoverblogpercona.commanual myisam_recover_optionsblogpercona.commanual myisam_recover_optionsblogpercona.commanual myisam_repair_threadsblogpercona.commanual myisam_sort_buffer_sizeblogpercona.commanual myisam_stats_methodblogpercona.commanual myisam_use…
Post: MySQL Performance on Memory Appliance
March 31, 2008 By 23 Comments
… and sending it back to the client. I tested MyISAM with myisam_use_mmap option which did not seems to give any significant performance… best conditions I got about 13.5K queries/sec from MyISAM (double of Innodb already) which scaled to 70.000 queries/sec peaking out at 16 threads. However even with MyISAM we got CPU bound before we could reach the system…
Comment: MyISAM mmap feature (5.1)
July 4, 2006 By 10 Comments
Vadim, Does –myisam_use_mmap=1 require any changes in ulimit -n settings? It is about MySQL bug #19800…
Comment: Evaluating IO subsystem performance for MySQL Needs
March 5, 2008 By 23 Comments
… and Sort files are absolutely unrelated to BBU because these use MyISAM and so buffered IO so writes to them can be… PageCache should be used to cache data instead of Innodb Buffer Pool, well this first would require to use mmap IO because you…
Comment: MyISAM mmap feature (5.1)
August 17, 2008 By 10 Comments
[...] now MySQL is using mmap() just for packed MyISAM files. Vadim wrote a patch to do more of [...]
Comment: MongoDB Approach to database synchronization
April 30, 2010 By 4 Comments
… keeping me active. I have no doubt that MongoDB and MyISAM are useful. But I wonder whether enough users understand the crash… the transactions from the last second. The behavior for MongoDB/MyISAM allows you to lose pieces from any transaction ever committed… via mmap and there can be a crash in the middle of writing a page leading to a corrupt page. For MyISAM…
Post: Are larger buffers always better ?
June 6, 2006 By 9 Comments
… is allocated fully in user space, while 32M block requires mmap() call and a lot of work with tables. In this…(11) default NULL, PRIMARY KEY (`id`), KEY `d` (`d`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 select sql_no_cache count(*) from t1…_buffer_size and read_rnd_buffer_size – These are buffers used by MyISAM to perform reads, in different scenarios. So should we…
Page: About This Blog
May 3, 2006 By 48 Comments
… Server performance as well as in performance of application stacks using MySQL, especially LAMP. Web sites handling millions of visitors a… – SHOW MUTEX STATUS, Tuning Innodb mutexes and concurrency control, MMAP IO for MyISAM tables, Innodb Auto-increment optimizations. My recent work in…
Comment: Thoughts on MySQL Replication
July 9, 2006 By 18 Comments
…. MyISAM row cache in memcached could be interesting and actually not that hard to implement. We’ve recently implemented IO via mmap… a year before it will be ready for serious production use. Speaking about Linux page cache efficiency – yes, thanks for catching…
