Support cachegrind as a tool

[mohe2015]

Hi,

when you want to diff two profiles using cg_annotate --diff it seems like this is only possible for cachegrind but not callgrind. Would it be possible to add support for running cachegrind too?

[gamma0987]

Hi. Yeah, callgrind diffs are only possible with flamegraphs but not with a command-line tool in the terminal. There is a the option to produce differential flamegraphs with

LibraryBenchmarkConfig::default()
    .flamegraph(FlamegraphConfig::default().kind(FlamegraphKind::Differential))

and you can view the resulting svg file in the browser.

Although adding cachegrind to the tools is certainly possible, there won't be a calibration run or something similar to optimize the statistics to the benchmarking function as it is possible with callgrind. So far, it didn't make much sense to offer a cachegrind run...

However, with the upcoming release of iai-callgrind there are the valgrind client requests available and since valgrind version v3.22, the cachegrind client requests start_instrumentation and stop_instrumentation, so maybe it starts making sense to add cachegrind to the available tools.

[gamma0987]

I thought a little bit more about this and I currently see two different possibilities. Add an option to run cachegrind (with all limitations) instead of callgrind. Or, add an option to run cachegrind in addition to callgrind. In both cases you're on your own to optimize the benchmark run for example with client requests if your valgrind version is recent enough. What do you think?

Out of curiosity, have you tried differential flamegraphs? Or, do you still prefer cg_annotate --diff?