Basically, it's a small header, and then events, plopped one after another into the file. Each thread gets a buffer to store events as they come in, and they get written as atomic chunks with fwrite/append, so threads never have to interact directly.
In practice, the overhead for tracepoints with the binary format is super low, depending on the machine on x86, we've seen somewhere between 12-20ns for begin+end trace overhead when compiled with clang (+ occasional disk flush overhead, if you're generating a ton of data). I believe I can get that overhead even smaller to get things nice and lightweight, it's a major goal of mine to be able to trace 10+ million events per second without impacting runtimes significantly, so that bigger projects can be comfortably fully auto-traced.
Ah neat. Have you ever used RAD Tools Telemetry (http://www.radgametools.com/telemetry.htm)? I saw Jonathan Blow using it on Youtube once and it looked slick and performant like Spall (and unlike every other open source option).
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So, spall has a JSON parser to help all the poor folks stuck using JSON or the chrome devtools profiler, who still need to keep using it.
For everyone doing new things, there's a binary format which is pretty straightforward.
The binary side supports begin and end events, which are defined here: https://github.com/colrdavidson/spall/blob/master/formats/sp...
and the header library mirrors those structs, and chalks out the interfaces around here: https://github.com/colrdavidson/spall/blob/master/spall.h#L2...
Basically, it's a small header, and then events, plopped one after another into the file. Each thread gets a buffer to store events as they come in, and they get written as atomic chunks with fwrite/append, so threads never have to interact directly.
In practice, the overhead for tracepoints with the binary format is super low, depending on the machine on x86, we've seen somewhere between 12-20ns for begin+end trace overhead when compiled with clang (+ occasional disk flush overhead, if you're generating a ton of data). I believe I can get that overhead even smaller to get things nice and lightweight, it's a major goal of mine to be able to trace 10+ million events per second without impacting runtimes significantly, so that bigger projects can be comfortably fully auto-traced.
Ah neat. Have you ever used RAD Tools Telemetry (http://www.radgametools.com/telemetry.htm)? I saw Jonathan Blow using it on Youtube once and it looked slick and performant like Spall (and unlike every other open source option).