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09 Jul 09

Choosing innodb_buffer_pool_size | MySQL Performance Blog

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Mysql innodb memory

My last post about Innodb Performance Optimization got a lot of comments choosing proper innodb_buffer_pool_size and indeed I oversimplified things a bit too much, so let me write a bit better description.

Innodb Buffer Pool is by far the most important option for Innodb Performance and it must be set correctly. I’ve seen a lot of clients which came through extreme sufferings leaving it at default value (8M). So if you have dedicated MySQL Box and you’re only using Innodb tables you will want to give all memory you do not need for other needs for Innodb Buffer Pool.

This of course assumes your database is large so you need large buffer pool, if not – setting buffer pool a bit larger than your database size will be enough. You also should account for growth of course. You need buffer pool a bit (say 10%) larger than your data (total size of Innodb TableSpaces) because it does not only contain data pages – it also contain adaptive hash indexes, insert buffer, locks which also take some time. Though it is not as critical – for most workloads if you will have your Innodb Buffer Pool 10% less than your database size you would not loose much anyway.

You also may choose to set buffer pool as if your database size is already larger than amount of memory you have – so you do not forget to readjust it later. This is also valid approach as if it is Dedicated MySQL Server you may not have a good use for that memory anyway.
The next step would be to decide How Much Memory do you need for other needs. This needs would be OS needs – your system processes, page tables, socket buffers etc all need memory. I would put this to 256M for small sized boxes to 5% of memory size on the big boxes, though it can be even less than that. Besides Operating System needs you also have MySQL needs – these include MySQL buffers – query cache, key_buffer, mysql threads, temporary tables, per thread sort buffer which can be allocated. There are also things like innodb additional memory pool (which can grow more than memory you allocated for it, especially in case you have large amount of tables).

07 Aug 08

Want to Remember Everything You'll Ever Learn? Surrender to This Algorithm

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memory psychology algorithm

Piotr Wozniak's quest for anonymity has been successful. Nobody along this string of little beach resorts recognizes him as the inventor of a technique to turn people into geniuses. A portion of this technique, embodied in a software program called SuperMemo, has enthusiastic users around the world. They apply it mainly to learning languages, and it's popular among people for whom fluency is a necessity — students from Poland or other poor countries aiming to score well enough on English-language exams to study abroad. A substantial number of them do not pay for it, and pirated copies are ubiquitous on software bulletin boards in China, where it competes with knockoffs like SugarMemo.
SuperMemo is based on the insight that there is an ideal moment to practice what you've learned. Practice too soon and you waste your time. Practice too late and you've forgotten the material and have to relearn it. The right time to practice is just at the moment you're about to forget. Unfortunately, this moment is different for every person and each bit of information. Imagine a pile of thousands of flash cards. Somewhere in this pile are the ones you should be practicing right now. Which are they?
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- It predicts the future state of a person's memory and schedules information reviews at the optimal time. The effect is striking. Users can seal huge quantities of vocabulary into their brains. But for Wozniak, 46, helping people learn a foreign language fast is just the tiniest part of his goal. As we plan the days, weeks, even years of our lives, he would have us rely not merely on our traditional sources of self-knowledge — introspection, intuition, and conscious thought — but also on something new: predictions about ourselves encoded in machines.
- In the late 1800s, a German scientist named Hermann Ebbinghaus made up lists of nonsense syllables and measured how long it took to forget and then relearn them. (Here is an example of the type of list he used: bes dek fel gup huf jeik mek meun pon daus dor gim ke4k be4p bCn hes.) In experiments of breathtaking rigor and tedium, Ebbinghaus practiced and recited from memory 2.5 nonsense syllables a second, then rested for a bit and started again. Maintaining a pace of rote mental athleticism that all students of foreign verb conjugation will regard with awe, Ebbinghaus trained this way for more than a year. Then, to show that the results he was getting weren't an accident, he repeated the entire set of experiments three years later. Finally, in 1885, he published a monograph called Memory: A Contribution to Experimental Psychology. The book became the founding classic of a new discipline.
- As a student at the Poznan University of Technology in western Poland in the 1980s, Wozniak was overwhelmed by the sheer number of things he was expected to learn. But that wasn't his most troubling problem. He wasn't just trying to pass his exams; he was trying to learn. He couldn't help noticing that within a few months of completing a class, only a fraction of the knowledge he had so painfully acquired remained in his mind. Wozniak knew nothing of the spacing effect, but he knew that the methods at hand didn't work.
- If students nonetheless manage to become expert in a few of the things they study,
  
  it's not because they retain the material from their lessons but because they specialize in a relatively narrow subfield where intense practice keeps their memory fresh.
- The disadvantage of this comforting notion is that it's false. "The people who criticize memorization — how happy would they be to spell out every letter of every word they read?" asks Robert Bjork, chair of UCLA's psychology department and one of the most eminent memory researchers. After all, Bjork notes, children learn to read whole words through intense practice, and every time we enter a new field we become children again. "You can't escape memorization," he says. "There is an initial process of learning the names of things. That's a stage we all go through. It's all the more important to go through it rapidly." The human brain is a marvel of associative processing, but in order to make associations, data must be loaded into memory.
- Their results were impressive: The best time to study something is at the moment you are about to forget it. And yet — as Neisser might have predicted — that insight was useless in the real world. Determining the precise moment of forgetting is essentially impossible in day-to-day life.
- Instead, Wozniak has ridden SuperMemo into uncharted regions of self-experimentation. In 1999, he started making a detailed record of his hours of sleep, and now he's working to correlate that data with his daily performance on study repetitions. Psychologists have long believed there's a correlation between sleep and memory, but no mathematical law has been discovered. Wozniak has also invented a way to apply his learning system to his intake of unstructured information from books and articles, winnowing written material down to the type of discrete chunks that can be memorized, and then scheduling them for efficient learning. He selects a short section of what he's reading and copies it into the SuperMemo application, which predicts when he'll want to read it again so it sticks in his mind. He cuts and pastes completely unread material into the system, assigning it a priority. SuperMemo shuffles all his potential knowledge into a queue and presents it to him on a study screen when the time is right. Wozniak can look at a graph of what he's got lined up to learn and adjust the priority rankings if his goals change.
- For Wozniak, these misfires were less a product of scrambling than of an inevitable clash of goals. A person who understands the exact relationship between learning and time is forced to measure out his hours with a certain care. SuperMemo was like a genie that granted Wozniak a wish: unprecedented power to remember. But the value of what he remembered depended crucially on what he studied, and what he studied depended on his goals, and the selection of his goals rested upon the efficient acquisition of knowledge, in a regressive function that propelled him relentlessly along the path he had chosen. The guarantee that he would not forget what he learned was both a gift and a demand, requiring him to sacrifice every extraneous thing.
- The failure of SuperMemo to transform learning uncannily repeats the earlier failures of cognitive psychology to influence teachers and students. Our capacity to learn is amazingly large. But optimal learning demands a kind of rational control over ourselves that does not come easily. Even the basic demand for regularity can be daunting. If you skip a few days, the spacing effect, with its steady march of sealing knowledge in memory, begins to lose its force. Progress limps. When it comes to increasing intelligence, our brain is up to the task and our technology is up to the task. The problem lies in our temperament.
- As a science fiction fan, I had always assumed that when computers supplemented our intelligence, it would be because we outsourced some of our memory to them. We would ask questions, and our machines would give oracular — or supremely practical — replies. Wozniak has discovered a different route. When he entrusts his mental life to a machine, it is not to throw off the burden of thought but to make his mind more swift. Extreme knowledge is not something for which he programs a computer but for which his computer is programming him.

SourceForge.net: SugarMemo - learning tool for memorizing

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memory learning tool

04 Jun 08

The Phoenix System for MapReduce Programming

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memory MapReduce

29 Mar 07

Virtual Threads: Understanding memory usage on Linux

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linux memory

03 Oct 06

Jack Slocum’s Blog » 3 Easy Steps to Avoid JavaScript Memory Leaks

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javascript js leak memory

You may not know it, but almost every site you visit that uses JavaScript is leaking memory. That may sound like an exaggeration, but it’s true. Don’t believe me?

Leak Monitor

With this handy extension for FireFox, any time you leave a page and it leaves code pointing to JavaScript objects - it displays a popup with details about the leak. It even gives you details about the function or object that created the leak.

02 Mar 06

Simple Memorizing Techniques

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memory tips

First, memory works by association. Our mind is a complex web of interconnected
thoughts and when one thing is called to mind, related concepts are
automatically triggered. We can’t hear the name ‘Romeo’ without thinking
‘Juliet’. Drinking café au lait with a croissant immediately reminds us of
Paris.

BrainConnection.com - How We Remember, and Why We Forget - Page 1

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memory

I remember my mother's vegetable garden when I was a child, corn plants tall
like skyscrapers. I remember when I fell out of a tree and everyone from the
neighbor's barbecue rushed over to see if I'd broken a bone.
subconscious. Modern descriptions are dominated by analogies to computers, in
which the human brain is a hard disk that stores experience in electronic files
and folders. Typical of biology, the truth is at once more complicated and more
beautiful than any of these descriptions.