daverigby

• Lambda t1 (lines 97-101):

(gdb) disas /s 0x00000000004cd7ce
Dump of assembler code for function ScopedEventBaseThreadTest_keepalive_Test::<lambda()>::operator()(void) const:
/home/couchbase/couchbase/tlm/deps/packages/build/folly/follytsan-prefix/src/follytsan/folly/io/async/test/ScopedEventBaseThreadTest.cpp:
97	  std::thread t1([&] {
   0x00000000004cd74c <+0>:	push   %rbp
   0x00000000004cd74d <+1>:	mov    %rsp,%rbp
   0x00000000004cd750 <+4>:	push   %rbx
   0x00000000004cd751 <+5>:	sub    $0x2b8,%rsp

daverigby

[ RUN      ] ExecutorPoolEpEngineTest/1.cancel_can_schedule
[New Thread 0x7ffff1547700 (LWP 11270)]
==================
WARNING: ThreadSanitizer: data race (pid=11268)
  Write of size 4 at 0x7fffffffde5c by main thread:
    #0 folly::EventBase::runInEventBaseThreadAndWait(folly::Function<void ()>) /home/couchbase/jenkins/workspace/cbdeps-platform-build-old/deps/packages/build/folly/follytsan-prefix/src/follytsan/folly/io/async/EventBase.cpp:661 (ep-engine_ep_unit_tests+0x00000171e04e)
    #1 FollyExecutorPool::unregisterTaskable(Taskable&, bool) ../kv_engine/engines/ep/src/folly_executorpool.cc:615 (ep-engine_ep_unit_tests+0x00000062f2b1)
    #2 KVBucket::deinitialize() ../kv_engine/engines/ep/src/kv_bucket.cc:489 (ep-engine_ep_unit_tests+0x000000676e45)
    #3 EPBucket::deinitialize() ../kv_engine/engines/ep/src/ep_bucket.cc:316 (ep-engine_ep_unit_tests+0x0000005ae8d8)
    #4 EventuallyPersistentEngine::~EventuallyPersistentEngine() ../kv_engine/engines/ep/src/ep_engine.cc:6548 (ep-engine_ep_unit_tests+0x0000

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/ClangBuildAnalyzer --analyze debug-build-1b.capture 
Analyzing build trace from 'debug-build-1b.capture'...
**** Time summary:
Compilation (348 times):
  Parsing (frontend):         1573.1 s
  Codegen & opts (backend):    317.4 s

**** Files that took longest to parse (compiler frontend):
 18032 ms: /Users/dave/repos/couchbase/server/source/build-debug/kv_engine/engines/ep/tests/CMakeFiles/ep-engine_ep_unit_tests.dir/module_tests/evp_store_single_threaded_test.cc.o
 16909 ms: /Users/dave/repos/couchbase/server/source/build-debug/kv_engine/engines/ep/tests/CMakeFiles/ep-engine_ep_unit_tests.dir/module_tests/dcp_stream_test.cc.o

daverigby

Step 1 - Gather profile

1. Install debuginfo package (in addition to main RPM/deb)
2. Install linux perf tools:
   • RHEL / CentOS / Amazon Linux: yum install perf.
   • Note: CentOS7 has a pretty old version of perf; which includes some issues decoding backtraces via DWARF. Prefer a newer version if possible. I have a local build of 5.11 for CentOS7 at ~/Documents/linux-perf-5.11-with-separate_debuginfo_unwind_fix
3. Start workload to be measured
4. Record profile
   1. x86-64:

daverigby

1. Install package libstdc++6 (Ubuntu 16.04)
2. Add following to ~/.gdbinit

python
import sys 
sys.path.insert(0, '/usr/share/gcc-9/python')
from libstdcxx.v6.printers import register_libstdcxx_printers
register_libstdcxx_printers (None)
end

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https://aras-p.info/blog/2019/01/16/time-trace-timeline-flame-chart-profiler-for-Clang/

-ftime-trace

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# From the host:
$ nsenter -t <PID as seen by host> /bin/bash
$ perf top / perf report etc.

daverigby

#include <functional>

using Raw = int (*)(const char* key, size_t klen, 
                    const char* val, size_t vlen);

using Func = std::function<int(const char* key, size_t klen, 
                    const char* val, size_t vlen)>;


volatile int count = 0;

daverigby

install/bin/erl
1> erlang:load_nif("install/lib/couchdb/erlang/lib/mapreduce-1.0/priv/mapreduce_nif", 0).

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#include <iostream>
#include <list>
#include <vector>

using Container = std::list<int>;

void print(const Container& v) {
  std::cout << "[";
  for (auto& e : v) {
    std::cout << e << " ";