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Tag Archives: performance
again, on benchmarks
Dear interweb, if you have no idea what you’re writing about, keep it to yourself, don’t litter into the tubes. Some people may not notice they’re eating absolute crap and get diarrhea. This particular benchmark has two favorite parts, that … Continue reading
On file system benchmarks
I see this benchmark being quoted in multiple places, and there I see stuff like: When carrying out more database benchmarking, but this time with PostgreSQL, XFS and Btrfs were too slow to even complete this test, even when it … Continue reading
iostat -x
My favorite Linux tool in DB work is ‘iostat -x’ (and I really really want to see whenever I’m doing any kind of performance analysis), yet I had to learn its limitations and properties. For example, I took 1s snapshot … Continue reading
Eyecandy mutexes!
In my quest of making MySQL usable, I managed to hit contention that wasn’t spotted by performance masters before. Meet most useless mutex ever (this is actual contention event, not just a hold): Count nsec Lock 1451 511364 mysqld`ut_list_mutex nsec … Continue reading
On SSDs, rotations and I/O
Every time anyone mentions SSDs, I have a feeling of futility and being useless in near future. I have spent way too much time to work around limitations of rotational media, and understand the implications of whole vertical data stack … Continue reading
On XFS write barriers
I’m very naive, when I have to trust software. I just can’t believe a filesystem may have a tunable that makes it 20x faster (or rather, doesn’t make it 20x slower). I expect it to work out of the box. … Continue reading
Progress in percents: 0 1 2 3 …
Well, servers usually don’t crash ( our English Wikipedia master is running for 800 days, on white-box hardware, RAID0, 4.0 ;-), but when they do (like some kernel bugs on our big big boxes), one of most painful experiences is … Continue reading
dtrace!
At the MySQL developer conference I accidently showed up some of things we’ve been doing with dtrace (I used it in few cases and realized the power it has), and saw some jaws drop. Then I ended up doing small demos … Continue reading
On blocking
If a process has two blocking operations, each blocking other (like, I/O and networking), theoretical performance decrease will be 50%. Solution is very easy – convert one operation (quite often the one that blocks less, but I guess it doesn’t … Continue reading
On checksums
InnoDB maintains two checksums per buffer pool block. Old formula of checksum, and new formula of checksum. Both are read, both are written. I guess this had to be some kind of transition period, but it obviously took too long … Continue reading