profiling – Page 8 – Türker Yıldırım

A sampling profiler is the one for production

NoteApril 2, 20201 min read

An instrumenting profiler records every call, which changes the timings it is measuring — small fast functions look disproportionately expensive because the overhead is per call. Sampling belongs…

wp profile finds the plugin before you read forty of them

NoteMarch 24, 20202 min read

Profiling a slow WordPress page usually starts with guessing which plugin is responsible, and there is a command that answers it directly. Drilling from stage to hook to…

A microbenchmark that mostly measures the benchmark

NoteJanuary 22, 20202 min read

Timing a function in a loop measures the loop, the opcache state, the CPU frequency scaling and occasionally the garbage collector — and rarely the function. The empty-loop…

An index that was never used, and the week it took to prove it

Deep diveNovember 8, 201910 min read

Forty indexes on one table and nobody willing to drop any of them. Invisible indexes turn a guess into a week of production traffic as evidence.

EXPLAIN ANALYZE shows what happened, not what might

NoteOctober 29, 20191 min read

EXPLAIN reports the plan and the optimiser’s estimates, and the estimates are frequently wrong — a query planned for 40 rows that reads 400,000 looks entirely healthy. The…

The N+1 in the ORM you cannot see from the template

Deep diveOctober 17, 201910 min read

Subquery selects in 6.0, and the aggregate that used to be a loop. Eager loading is all-or-nothing per relation, which is the problem.

A flame graph’s x axis is not time

NoteSeptember 19, 20191 min read

The instinct is to read it left to right as a timeline, and the x axis is alphabetical — a wide block is total time across the whole…

The queue worker that leaked, and the memory limit that hid it

Deep diveJuly 15, 201910 min read

A worker restarting every eleven minutes, reported as healthy. Finding the leak is not the same as bounding it, and the seatbelt hides the next one.

Lazy collections and the report that would not fit in memory

Deep diveJune 24, 201910 min read

A memory limit hit on the fourth of the month, every month. A collection is an array, and an array is all of it at once — until…

A sampling profiler is the one that belongs in production

NoteMay 28, 20192 min read

An instrumenting profiler records every function call, which changes the timings it is measuring — small fast functions look disproportionately expensive because the overhead is per call. Sampling…