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Tag Archives: performance
On connections
MySQL is needlessly slow at accepting new connections. People usually work around that by having various sorts of connection pools, but there’s always a scale at which connection pools are not feasible. Sometimes connection avalanches come unexpected, and even if … Continue reading
InnoDB locking makes me sad
Vadim and others have pointed at the index->lock problems before, but I think they didn’t good job enough at pointing out how bad it can get (the actual problematic was hidden somewhere as some odd edge case). What ‘index lock’ … Continue reading
MySQL metrics for read workloads
There are multiple metrics that are really useful for read workload analysis, that should all be tracked and looked at in performance-critical environments. The most commonly used is of course Questions (or ‘Queries’, ‘COM_Select’) – this is probably primary finger-pointing … Continue reading
Posted in facebook, mysql
Tagged easy, innodb, monitoring, performance, profiling
A case for FORCE INDEX
I remember various discussions in different mediums where people were building cases against use of FORCE INDEX in SQL queries. I’ll hereby suggest it using way more often, but at first I’ll start with small explanation. For ages, the concept … Continue reading
random poking
These are some of my notes from some sysbench in-memory r/o testing in past day or so: At ‘fetch data by primary key’ benchmark with separate read snapshots at each statement, MySQL shines until ~200 concurrent threads, then performance starts … Continue reading
on performance stalls
We quite often say, that benchmark performance is usually different from real world performance – so performance engineering usually has to cover both – benchmarks allow to understand sustained performance bottlenecks, and real world analysis usually concentrates on something what … Continue reading
Postgres kernel regressions
While Mark was looking at MongoDB, I was playing comparing various aspects of MySQL and Postgres performance. Certain PG performance numbers I saw (40kqps vs 110kqps from MySQL) made me really upset, so I ended up discussing with people at … Continue reading
Opening tables v2!
PMP on demand revealed one of reasons why we’ve been seeing ‘Opening tables’ during proper operations, not just during startup (see my previous post on this topic). We had a thousand or so threads waiting on LOCK_open, and the only … Continue reading
Crash recovery, again
There’s one stage in InnoDB crash recovery where it reads log file, you know, this one: InnoDB: Doing recovery: scanned up to log sequence number 354164119040 InnoDB: Doing recovery: scanned up to log sequence number 354169361920 On a machine with … Continue reading
Posted in mysql
Tagged crash, innodb, performance, recovery
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
