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runtime: improve "sweep increased allocation count" diagnostics #21729

aclements opened this issue Sep 1, 2017 · 1 comment

runtime: improve "sweep increased allocation count" diagnostics #21729

aclements opened this issue Sep 1, 2017 · 1 comment


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@aclements aclements commented Sep 1, 2017

The infamous "sweep increased allocation count" panic is not very informative. What it really means is that a free object was found to be live. It should say that, and it should say which object it is and dump its contents. Essentially, it can cheaply give half of the information that gccheckmark can. This half may even be enough to debug the problem from a core dump and a heap graph.

The comments around the panic should give additional context (not worth printing), like saying that common causes are bad liveness maps, past-the-end pointers, unsafe conversions from pointers to integers and back to pointers, and just plain wild pointers. The comments should suggest running with GODEBUG=gccheckmark=1 to find the source of bad pointer.

/cc @RLH @randall77


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@jiacai2050 jiacai2050 commented Dec 16, 2019

Is anyone working on this? This tricky issue happens several times one day in my app, the stack log is useless for debugging.

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