SysBench – benchmark tool

Aug 18, 2006 | Benchmarks

Sysbench is benchmark developed by Alexey Kopytov (software engineer @ MySQL AB) – http://sysbench.sourceforge.net/ and I want to write a short intro about this tool as sysbench is one of software for my everyday use. For example, SUN published their Solaris vs RedHat stuff based on sysbench’s results (Peter and me provided performance consutling for […]

Returning to InnoDB scalability

Jul 28, 2006 | Insight for DBAs

I’m again returning to InnoDB scalability and related bug #15815 as it hurts many users and customers using multi-cpu servers. Short intro into problem: On 4-CPU box 1 thread executes full-table scan select query for 8 sec, but with 4 threads – each thread executes query for 240 sec. It is very strange as threads […]

Stack trace for x86_64 boxes

Jul 19, 2006 | Insight for DBAs

We are going to release several patches which are not included in official MySQL releases. First one is automatically stack trace for x86_64 systems. Currently MySQL resolves stack in crash only for x86 boxes. You can download patch for 5.0.22 source tree here. How to use: place stack64.diff into main source dir; execute patch -p1 […]

Handling big result sets

Jun 26, 2006 | Insight for Developers

Sometime it is needed to handle a lot of rows on client side. Usual way is send query via mysql_query and than handle the result in loop mysql_fetch_array (here I use PHP functions but they are common or similar for all APIs, including C). Consider table:

FreeBSD tests

Jun 15, 2006 | Benchmarks

I’m continuing my experiments with different OS and today I tested FreeBSD 6.0 on my box. (more details about box and benchmark see here https://www.percona.com/blog/2006/06/13/quick-look-at-ubuntu-606/). Initially I was very pessimistic about FreeBSD, as results were (in transactions/sec, more is better. for comparison the results from Suse 10.0): InnoDB threads FreeBSD 6 Suse 10.0 Suse/ FreeBSD […]

MyISAM concurrent insert

Jun 13, 2006 | Benchmarks, Insight for DBAs

Arjen posted a good note about MyISAM concurrent-insert features, though I should mention concurrent-insert can be cause of scalablity and peformance problems on SMP boxes, especially on queries processing range-queries. The reason of problems is POSIX read-write locks, which are used to protect key_buffer from concurrent changes and called for each processed row. More info […]

Quick look at Ubuntu 6.06

Jun 13, 2006 | Benchmarks

There are a lot of talks around new coming Ubuntu 6.06, so I decided to make quick benchmarks. I used sysbench 0.4.6 oltp-read-only workload with 1000000 rows against InnoDB and MyISAM tables. Such workload is CPU-bound and allows to compare CPU / OS if we are using the same version of MySQL. So I used […]

How InnoDB Thread Concurrency Works

Jun 05, 2006 | Insight for DBAs

InnoDB has a mechanism to regulate count of threads working inside InnoDB. innodb_thread_concurrency is variable which set this count, and there are two friendly variables innodb_thread_sleep_delay and innodb_concurrency_tickets. I’ll try to explain how it works. MySQL has pluginable architecture which divides work between mysql common code (parser, optimizer) and storage engine. From storage engine’s point […]

InnoDB page size

Jun 04, 2006 | Insight for DBAs

As maybe you know InnoDB uses hard page size 16Kb for datafiles and for buffer pool. However this size can be changed if you need it for your workload. go to file innobase/include/univ.i, lines:

UNIV_PAGE_SIZE is page size (as you see – default value 16Kb). Possible values for UNIV_PAGE_SIZE is 8K, 16K, 32K, 64K. […]

Indexes in MySQL

Jun 02, 2006 | Insight for DBAs

MySQL does not always make a right decision about indexes usage. Condsider a simple table:

; 250001 (V1)

; 83036 (V2) (execution time = 110 ms) That is index selectivity by condition (ID1=1) is V2/V1 = 0.3321 or 33.21% It is said (e.g. book “SQL Tuning”) if selectivity over 20% then a full table […]

InnoDB memory usage

May 30, 2006 | Insight for DBAs

There are many questions how InnoDB allocates memory. I’ll try to give some explanation about the memory allocation at startup. Some important constants: NBLOCKS=count of block in innodb_buffer_pool = innodb_buffer_pool_size / 16384 OS_THREADS= if (innodb_buffer_pool_size >= 1000Mb) = 50000 else if (innodb_buffer_pool_size >= 8Mb) = 10000 else = 1000 (it’s true for *nixes, for Windows […]

MyISAM mmap feature (5.1)

May 26, 2006 | Insight for DBAs

As you know MyISAM does not cache data, only indexes. MyISAM assumes OS cache is good enough and uses pread/pwrite system calls for reading/writing datafiles. However OS is not always good in this task, my benchmarks show Linux/Solaris aren’t scalable on intensive pread calls (I believe the same for Windows, but I did not test […]

Group commit and XA

May 19, 2006 | Insight for DBAs

Returning to post Group commit and real fsync I made several experiments: I ran sysbench update_key benchmarks without —log-bin, with —log-bin, and with —log-bin and —innodb-support-xa=0 (default value is 1). Results (in transactions / sec) threads without —log-bin —log-bin —log-bin and —innodb_support-xa=0 1 1218.68 614.94 1010.44 4 2686.36 667.77 1162.60 16 3993.59 666.14 1161.56 64 […]

Mess with innodb_thread_concurrency

May 12, 2006 | Insight for DBAs

In MySQL 5.0.19 the meaning of innodb_thread_concurrency variable was changed (yeah, again). Now innodb_thread_concurrency=0 means unlimitied count of concurrent threads inside InnoDB. It’s logical, but there was long way. In MySQL versions below 5.0.8 for unlimited threads you had to set innodb_thread_concurrency over 500 (and default value for innodb_thread_concurrency was 8 ). Starting with MySQL […]