[Lldb-commits] [PATCH] D122848: Reduce extraneous temp strings in debugserver, free objects when they're not longer needed

[Jason Molenda via Phabricator via lldb-commits]

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Looking at debugserver's memory use a bit, I noticed that the SendPacket method which takes a std::string& argument, is often called with a std::string object that the caller calls c_str() on, so a temporary copy of the string is created.  This patch removes those c_str() method calls.

We also have a common pattern where we have/create a JSONGenerator::ObjectSP, dump the string representation of the object into a ostringstream, and then binary escape the ostringstream.  We end up with the original ObjectSP dictionary, the ostringstream print of it, and the escaped std::string copy of it.  Then we pass that to SendPacket which may create a compressed std::string of it.  This patch frees those objects as soon as they are no longer needed, so our peak memory use is limited to a narrower window.

In the future I want to add a JSONGenerator::DumpEscaped() method that formats its output following the binary escape protocol.  Every packet that sends JSON responses must escape it before sending, so there's no point in even generating the un-escaped version in the first place.  It forces us to always have two copies of the string in heap for at least a little while.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D122848

Files:
  lldb/tools/debugserver/source/RNBRemote.cpp

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