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runtime: "sweep increased allocation count" on linux-amd64-staticlockranking builder #38702
A zombie slot is a slot that is marked, but isn't allocated. This can indicate a bug in the GC, or a bad use of unsafe.Pointer. Currently, the sweeper has best-effort detection for zombie slots: if there are more marked slots than allocated slots, then there must have been a zombie slot. However, this is imprecise since it only compares totals and it reports almost no information that may be helpful to debug the issue. Add a precise check that compares the mark and allocation bitmaps and reports detailed information if it detects a zombie slot. No appreciable effect on performance as measured by the sweet benchmarks: name old time/op new time/op delta BiogoIgor 15.8s ± 2% 15.8s ± 2% ~ (p=0.421 n=24+25) BiogoKrishna 15.6s ± 2% 15.8s ± 5% ~ (p=0.082 n=22+23) BleveIndexBatch100 4.90s ± 3% 4.88s ± 2% ~ (p=0.627 n=25+24) CompileTemplate 204ms ± 1% 205ms ± 0% +0.22% (p=0.010 n=24+23) CompileUnicode 77.8ms ± 2% 78.0ms ± 1% ~ (p=0.236 n=25+24) CompileGoTypes 729ms ± 0% 731ms ± 0% +0.26% (p=0.000 n=24+24) CompileCompiler 3.52s ± 0% 3.52s ± 1% ~ (p=0.152 n=25+25) CompileSSA 8.06s ± 1% 8.05s ± 0% ~ (p=0.192 n=25+24) CompileFlate 132ms ± 1% 132ms ± 1% ~ (p=0.373 n=24+24) CompileGoParser 163ms ± 1% 164ms ± 1% +0.32% (p=0.003 n=24+25) CompileReflect 453ms ± 1% 455ms ± 1% +0.39% (p=0.000 n=22+22) CompileTar 181ms ± 1% 181ms ± 1% +0.20% (p=0.029 n=24+21) CompileXML 244ms ± 1% 244ms ± 1% ~ (p=0.065 n=24+24) CompileStdCmd 15.8s ± 2% 15.7s ± 2% ~ (p=0.059 n=23+24) FoglemanFauxGLRenderRotateBoat 13.4s ±11% 12.8s ± 0% ~ (p=0.377 n=25+24) FoglemanPathTraceRenderGopherIter1 18.6s ± 0% 18.6s ± 0% ~ (p=0.696 n=23+24) GopherLuaKNucleotide 28.7s ± 4% 28.6s ± 5% ~ (p=0.700 n=25+25) MarkdownRenderXHTML 250ms ± 1% 248ms ± 1% -1.01% (p=0.000 n=24+24) [Geo mean] 1.60s 1.60s -0.11% (https://perf.golang.org/search?q=upload:20200517.6) For #38702. Change-Id: I8af1fefd5fbf7b9cb665b98f9c4b73d1d08eea81 Reviewed-on: https://go-review.googlesource.com/c/go/+/234100 Run-TryBot: Austin Clements <firstname.lastname@example.org> TryBot-Result: Gobot Gobot <email@example.com> Reviewed-by: Cherry Zhang <firstname.lastname@example.org>
@toothrot I don't think we've seen this crash since the failure that caused Bryan to open this issue. @aclements' CL should give us a lot more information should we see this crash again, though. I think it's probably safe to not mark this as a beta-blocking issue, but we should keep an eye out for more such failures.
Also an interesting data point: it looks like all the failures that were happening through March were happening with the same size class (
I think the only two crashes relevant to this thread are: