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by bee_rider 1639 days ago
Awesome! Hopefully the distros will keep up.

I saw in some other comments you mentioned some performance lift coming from thread level parallelism in Go. I wonder -- can you get oversubscription issues if the user is doing their own parallelism (I assume some folks will implement 'parallelism' by throwing a bunch of independent processes at a bunch of independent records).

I know in openMP (for example) this would be something where the user is expected to keep track of it, but maybe the Go runtime handles this stuff gracefully?
2 comments
john_kerl 1639 days ago
Also re 'hopefully the distros will keep up' -- some do some don't. I hope the C-to-Go issue isn't too much of a speedbump but we should know a couple distros in.

The other day I ran across https://repology.org/project/miller/versions -- something autogenerated on the web; I don't maintain it. Anyway you can see most distros are on 5.10 but there are some farther behind ... I will probably start with Conda and Brew since these are more personal/interactive, then maybe Fedora and Ubuntu -- ?

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vcdimension 1638 days ago
A guix version would be nice...
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john_kerl 1639 days ago
Indeed -- in Go technically it's "concurrency" not "parallelism" (something the Go folks are careful to articulate) but with multiple processors available, in effect you get multicore processing so calling it "parallelism" isn't far off :).

More specifically, Miller uses separate "goroutines" (more or less threads) -- 2 for input (one for raw byte stream ingest and one for forming records), 1 for each verb (sort then head would be two verbs), and 1 for output (records back to strings), all pipelined up. Some of the recent perf improvements came from splitting the record-reader into two concurrent goroutines like that. Some of the older perf improvements are from pipelining the verbs.

But yes, if you have say 16 CPUs and you launch 10, or 20, or 30 Miller executables -- in the C impl each would soak a single CPU and anything beyond 16, the OS would have to multitask things. With Miller 6, basically the same kind of thing except each executable will be trying to use more than one CPU if it can. If it can't, the Go runtime and the OS will multitask. And both do tend to handle this stuff gracefully and without tuning on the part of the user.

Also I'd point out that even with big files & deeper multi-verb processing chains, htop rarely shows over 250% CPU, maybe 350% for deeper chains -- the input and output processing typically take most of the time, and the verbs in between not as much.

When we run out of memory, systems crash; when we run out of CPU, things just take a bit longer. I.e. the oversubscription is a real but non-fatal issue, for C or for Go ...

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