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Displaying posts with tag: ibm (reset)

doing nothing on modern CPUs
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Sometimes you don’t want to do anything. This is understandably human, and probably a sign you should either relax or get up and do something.

For processors, you sometimes do actually want to do absolutely nothing. Often this will be while waiting for a lock. You want to do nothing until the lock is free, but you want to be quick about it, you want to start work once that lock is free as soon as possible.

On CPU cores with more than one thread (e.g. hyperthreading on Intel, SMT on POWER) you likely want to let the other threads have all of the resources of the core …

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The sad state of MySQL and NUMA
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Way back in 2010, MySQL Bug 57241 was filed, pointing out that the “swap insanity” problem was getting serious on x86 systems – with NUMA being more and more common back then.

The swapping problem is due to running out of memory on a NUMA node and having to swap things to other nodes (see Jeremy Cole‘s blog entry also from 2010 on the topic of swap insanity). This was back when 64GB and dual quad core CPUs …

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MariaDB with Galera available on the IBM Power8 platform
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It was a very long time since I wrote something in this blob, but I have been very busy this spring with MariaDB on Power mostly. This has been a lot of work, but also a lot of fun. So, what is this MariaDB on Power thing all about, well I wrote an introduction to the Power platform late last year. Since then a lot of things has happened though.

One thing is that several service providers out there has adopted Power8 as a platform. To be honest, this really isn't sexy, but it is useful and as a user of one of …

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Going beyond 1.3 MILLION SQL Queries/second
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So, on a large IBM POWER8 system I was recently running the newly coined “yesmark” benchmark, which is best translated as this:

Benchmark (N for concurrency): for i in {1..N}; do yes "DO 0;" | mysql > /dev/null & done
Live results: mysqladmin -ri 1 extended-status | grep Questions

Which sounds all fun until you realize that it’s *amazingly* close in results to a sysbench point select benchmark these days (well, with MySQL 5.7.7).

Since yesmark doesn’t use InnoDB though, MariaDB is back in the game.

I don’t …

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C bitfields considered harmful
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In C (and C++) you can specify that a variable should take a specific number of bits of storage by doing “uint32_t foo:4;” rather than just “uint32_t foo”. In this example, the former uses 4 bits while the latter uses 32bits. This can be useful to pack many bit fields together.

Or, that’s what they’d like you to think.

In reality, the C spec allows the compiler to do just about anything it wants with these bitfields – which usually means it’s something you didn’t expect.

For a start, in a struct -e.g. “struct foo { uint32_t foo:4; uint32_t blah; uint32_t blergh:20; }” the …

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volatile considered harmful
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While playing with MySQL 5.7.5 on POWER8, I came across a rather interesting bug (74775 – and this is not the only one… I think I have a decent amount of auditing and patching to do now) which made me want to write a bit on memory barriers and the volatile keyword.

Memory barriers are hard.

Like, super hard. It’s the kind of thing that makes you curse hardware designers, probably because they’re not magically solving all your problems for you. Basically, as you get more CPU cores and each of them have caches, it gets more expensive to keep everything in sync. …

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Preliminary MySQL Cluster benchmark results on POWER8
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Yesterday, I got the basics going for MySQL Cluster on POWER. Today, I finished up a couple more patches to improve performance and ran some benchmarks.

This is on a 3.7Ghz POWER8 machine with non-balanced memory (only 2 of the 4 NUMA nodes have memory, so we have less total memory bandwidth than we could have, plus I’m going to bind ndbmtd to the CPUs in these NUMA nodes)

With a setup of a single replica and two data nodes on the one machine (each bound to a specific NUMA node), running the flexAsync benchmark …

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MySQL Cluster on POWER8
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So, I’ve written previously on MySQL on POWER, and today is a quick bit of news about MySQL Cluster on POWER – specifically MySQL Cluster 7.3.7.

I ran into three main issues in getting some flexAsync benchmark results. One of them was the fact that I wanted to do this in the middle of all the POWER8 machines I usually use moving buildings (hard to run benchmarks when computers are packed up in boxes on a truck).

The next issue was that ndbmtd (the multi-threaded data node) needs memory barriers for the magic message passing stuff between threads. So, that’s pretty easy (about an eight line patch).

The next issue was in the …

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MariaDB 10.0 on POWER
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Good news for those wanting to run MariaDB on POWER systems, the latest 10.0 bzr tree (as of a couple of weeks ago) builds and runs well!

I recently pulled the latest MariaDB 10.0 from BZR and built it on a POWER8 system in the lab to run some quick tests. The MariaDB team has done some work on getting MariaDB to run on POWER recently, a bunch of which is based off my work on MySQL on POWER.

There’s obviously still some work in progress going on, but my initial results show performance within around 10% of MySQL, so with a bit of work we will hopefully see MariaDB reach performance parity.

One interesting find was the code to …

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MySQL 5.6.20 on POWER
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It’s been a little while since I blogged on MySQL on POWER (last time was thinking that new releases would be much better for running on POWER). Well, I recently grabbed the MySQL 5.6.20 source tarball and had a go with it on a POWER8 system in the lab. There is good news: I now only need one patch to have it function pretty flawlessly (no crashes). Unfortunately, there’s still a bit of an odd thing with some of the InnoDB mutex code (bug filed at some point soon).

But, with this one patch applied, I was getting okay sysbench results and things are …

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Showing entries 1 to 10 of 65 10 Older Entries

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