mirror of https://github.com/golang/go.git
c4078a1998
Lines with single cells prompt a flush. Unfortunately, a call to Writer.Flush also means two defers, which is an expensive operation to do if many lines consist of single cells. This is common when formatting code with aligned comments. Most lines aren't going to have any comments at all, so the performance hit is going to be noticeable. The Write method already has a "defer handlePanic" of its own, so we don't need to worry about panics leaking out. The error will now mention "Write" instead of "Flush" if a panic is encountered during that nested flush, but arguably that's a good thing; the user called Write, not Flush. For the reset call, add a non-deferred call as part of flushNoDefers, as that's still necessary. Otherwise, the exported Flush method still does a "defer b.reset". The current tabwriter benchmarks are unaffected, since they don't contain many single-cell lines, and because lines are written one at a time. For that reason, we add a benchmark which has both of these characteristics. name old time/op new time/op delta Code-8 2.72µs ± 0% 1.77µs ± 0% -34.88% (p=0.000 n=6+5) name old alloc/op new alloc/op delta Code-8 648B ± 0% 648B ± 0% ~ (all equal) name old allocs/op new allocs/op delta Code-8 13.0 ± 0% 13.0 ± 0% ~ (all equal) Perhaps unsurprisingly, go/printer also gets a bit faster, as it too buffers its output before writing it to tabwriter. name old time/op new time/op delta Print-8 6.53ms ± 0% 6.39ms ± 0% -2.22% (p=0.008 n=5+5) Change-Id: Ie01fea5ced43886a9eb796cb1e6c810f7a810853 Reviewed-on: https://go-review.googlesource.com/c/go/+/166797 Run-TryBot: Daniel Martí <mvdan@mvdan.cc> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org> |
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