…. Mmap is available on all POSIX-compatible platforms. It will work faster for SELECT/UPDATE/INSERT inside file queries, and no performance… results (queries/sec, more is better): select-primary Threads Pread Mmap Mmap/pread ratio 1 8894.00 9393.73 1.06 4… memory mapping gives benefit in different cases. The value of performance gain depends of count replaced pread/pwrite calls. For select…
Post: Read Buffers, mmap, malloc and MySQL Performance
September 12, 2007 By 8 Comments
…_profile (often together with strace) are great tools for MySQL Performance analyses. Too many people end tuning on plans and indexes… next Monty comes up with 2 posts on mmap allocation. Indeed allocating with mmap is much slower than allocating from memory memory… indeed proportional to number of pages being allocated. On anonimous mmap (which is used for allocations) physical pages are typically not…
Post: MySQL Performance on Memory Appliance
March 31, 2008 By 23 Comments
… and with 256 threads I got even a bit better performance. Interesting enough utilization in iostat never went over few percents… Innodb took very high hit supplied with high performance IO subsystem. But not only performance was poor with single thread it also… with myisam_use_mmap option which did not seems to give any significant performance benefit, may be even reducing performance few percents. I…
Post: Ultimate MySQL variable and status reference list
January 8, 2011 By 4 Comments
…commanual myisam_mmap_sizeblogpercona.commanual…Performance_schema_mutex_classes_lostblogpercona.commanual Performance_schema_mutex_instances_lostblogpercona.commanual Performance_schema_rwlock_classes_lostblogpercona.commanual Performance_schema_rwlock_instances_lostblogpercona.commanual Performance…
Comment: Impact of memory allocators on MySQL performance
July 8, 2012 By 11 Comments
… we are comparing malloc performance, it is quite possible that something else may have worsened the performance of glibc over versions other… these allocators switch from sbrk to mmap. For glibc, according to documentation, it should be MMAP_THRESHOLD which is 128 kB though…
Post: Tokyo Tyrant - The Extras Part I : Is it Durable?
November 10, 2009 By 5 Comments
… me if you know better then I. Using mmap here and performing a kill -9 seems to preserve the changes in… write can severely degrade performance. Before I explain lets look at the performance hit: Saying there is a performance hit here is… my benchmark, heavy write operations will see a drop in performance… for instance with 8 threads simply update/inserting data is…
Post: Are larger buffers always better ?
June 6, 2006 By 9 Comments
… being wasted but you may see some of queries actually performing slower, and not because the system starts to swap. Generally…, while 32M block requires mmap() call and a lot of work with tables. In this extreme case performance difference was 9 seconds…_rnd_buffer_size – These are buffers used by MyISAM to perform reads, in different scenarios. So should we go ahead and…
Comment: Read Buffers, mmap, malloc and MySQL Performance
May 7, 2008 By 8 Comments
[...] MySQL Performance Blog: Read Buffers, mmap, malloc and MySQL Performance [...]
Comment: Read Buffers, mmap, malloc and MySQL Performance
March 6, 2008 By 8 Comments
[...] http://mysql-ha.com/2007/09/06/read-buffer-performance-hit/ http://www.mysqlperformanceblog.com/2007/09/12/read-buffers-mmap-malloc-and-mysql-performance/ [...]
Comment: MySQL: what read_buffer_size value is optimal ?
September 17, 2007 By 25 Comments
Like Monty wrote, the performance degradation is caused by the flip between regular malloc and mmap() at 256K (default): http://bonglonglong.com/2007/09/06/read-buffer-performance-hit/ -j
