[PATCH] D107800: [CSSPGO][llvm-profgen] Cap context stack to reduce memory usage

[Wenlei He via Phabricator via llvm-commits]

wenlei added inline comments.


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Comment at: llvm/tools/llvm-profgen/ProfileGenerator.cpp:53
+cl::opt<int> CSProfCtxStackCap(
+    "csprof-ctx-stack-cap", cl::init(20), cl::ZeroOrMore,
+    cl::desc("Cap context stack at a given depth. No cap if the input is -1."));
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I think we could unify the switch names, e.g. `csprof-max-context-depth` and `csprof-max-cold-context-depth`? 


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Comment at: llvm/tools/llvm-profgen/ProfileGenerator.cpp:615
   CSProfileGenerator::compressRecursionContext(ContextStrStack);
+  CSProfileGenerator::capContextStack(ContextStrStack, CSProfCtxStackCap);
 
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Since `getExpandedContextStr` only covers line-based profile, for probe we rely on the trimming here in profile generation, which is later then where we do the trimming for line-based profile. Do we see peak memory drop if we trim the context in profile generation instead of during unwinder? 


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Comment at: llvm/tools/llvm-profgen/ProfileGenerator.h:73
 
+  // Cap the context stack by cutting off from the bottom at a given depth.
+  template <typename T>
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nit: bottom-up order in stack is usually callers-callee order, from bottom can be confusing as it means we trim callees which is not the case. 

also suggest rename capContextStack to trimContext.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D107800/new/

https://reviews.llvm.org/D107800