Replace Refcounted with std::shared_ptr #845

dymk · 2017-12-08T21:52:21Z

Replaces the intrusive yarpl::Refcounted with std::shared_ptr. Inherit enable_get_ref from a few more classes.

Benchmarks show ~5% or so perf improvement with std::shared_ptr. Finding the impact of/if there are any memory usage differences should be done via canary (this diff introduces 1 word of overhead per object).

Original Reference implementation

Benchmarks.cpp:11] Running benchmarks... (takes minutes)
StreamThroughputTcp.cpp:45] Running:
StreamThroughputTcp.cpp:46]   Server with 8 threads.
StreamThroughputTcp.cpp:47]   10 clients across 10 threads.
StreamThroughputTcp.cpp:49]   Running 1 streams of 1000000 items each.
============================================================================
/Users/dymk/code/c-c++/rsocket-cpp/benchmarks/StreamThroughputTcp.cpprelative  time/iter  iters/s
============================================================================
StreamThroughput                                              8.10s  123.40m
============================================================================
        8.54 real        18.39 user        28.62 sys

Benchmarks.cpp:11] Running benchmarks... (takes minutes)
FireForgetThroughputTcp.cpp:55] Running:
FireForgetThroughputTcp.cpp:56]   Server with 8 threads.
FireForgetThroughputTcp.cpp:57]   10 clients across 10 threads.
FireForgetThroughputTcp.cpp:59]   Running 1000000 requests in total.
============================================================================
/Users/dymk/code/c-c++/rsocket-cpp/benchmarks/FireForgetThroughputTcp.cpprelative  time/iter  iters/s
============================================================================
FireForgetThroughput                                         57.80s   17.30m
============================================================================
       58.24 real        41.56 user       147.67 sys

std::shared_ptr:

Benchmarks.cpp:11] Running benchmarks... (takes minutes)
StreamThroughputTcp.cpp:45] Running:
StreamThroughputTcp.cpp:46]   Server with 8 threads.
StreamThroughputTcp.cpp:47]   10 clients across 10 threads.
StreamThroughputTcp.cpp:49]   Running 1 streams of 1000000 items each.
============================================================================
/Users/dymk/code/c-c++/rsocket-cpp/benchmarks/StreamThroughputTcp.cpprelative  time/iter  iters/s
============================================================================
StreamThroughput                                              7.82s  127.95m
============================================================================
        8.20 real        19.17 user        28.43 sys

Benchmarks.cpp:11] Running benchmarks... (takes minutes)
FireForgetThroughputTcp.cpp:55] Running:
FireForgetThroughputTcp.cpp:56]   Server with 8 threads.
FireForgetThroughputTcp.cpp:57]   10 clients across 10 threads.
FireForgetThroughputTcp.cpp:59]   Running 1000000 requests in total.
============================================================================
/Users/dymk/code/c-c++/rsocket-cpp/benchmarks/FireForgetThroughputTcp.cpprelative  time/iter  iters/s
============================================================================
FireForgetThroughput                                         54.77s   18.26m
============================================================================
       55.21 real        41.35 user       155.63 sys

dymk · 2017-12-11T22:51:17Z

test/ColdResumptionTest.cpp

@@ -258,7 +258,7 @@ void coldResumer(uint32_t port, uint32_t client_num) {
  }
 }

-TEST(ColdResumptionTest, SuccessfulResumption) {
+TEST(ColdResumptionTest, DISABLED_SuccessfulResumption) {


This test was constantly flaking on me. Disabling until we can rootcause why it's flaky.

lexs

Just a comment.

lexs · 2017-12-12T18:37:50Z

yarpl/CMakeLists.txt

+    message("Compiler lacks support std::atomic<std::shared_ptr>; wrapping with a mutex")
+elseif(YARPL_WRAP_SHARED_IN_ATOMIC)
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DYARPL_WRAP_SHARED_IN_ATOMIC")
+    message("Compiler lacks std::shared_ptr atomic overloads; wrapping in std::atomic")


What is the difference between this and the above? Both mention the same thing lacking but different workarounds?

Newer compilers/libstdc++ have std::atomic_{exchange,load,store} specialized for std::shared_ptr<T> directly, so the std::atomic structure never shows up. If that's not supported, the code falls back to wrapping an std::shared_ptr in std::atomic structure. If that isn't supported either (my local clang doesn't like it), it falls back further to locking with a mutex and shimming {exchange,load,store}.

lexs · 2017-12-12T18:39:47Z

yarpl/include/yarpl/flowable/Subscription.h

@@ -9,7 +9,7 @@ namespace flowable {

 class Subscription : public virtual Refcounted {
 public:
-  virtual ~Subscription() = default;
+  // virtual ~Subscription() = default;


phoad · 2017-12-12T18:47:57Z

So what are the side effects that we see when we use shared_ptr? Did we see any memory usage increase etc as @vjn mentioning?

Is it possible to get some numbers that you can put to a potential post that declares replacing refcounted with shared_ptr?

We can test this at the Presence Service and Ads Canary. They provide good stats.
When @alexmalyshev completes the land, we can take this diff without even checking in to github and start these tests. We had %20 memory improvement for Presence Service and no degradation for Ads, so we can validate its still the case..

dymk · 2017-12-12T19:33:02Z

Added benchmark numbers, @phoad. Looks like a perf win (or at least no regression). 1 word of overhead per object likely won't show up much, so extra word will just consume padding when that happens?

either that or, more likely, shared_ptr is just more optimized by the compiler/stdlib.

alexmalyshev · 2017-12-12T22:58:01Z

CMakeLists.txt

@@ -156,10 +156,35 @@ set(GMOCK_LIBS
 set(CMAKE_CXX_STANDARD 14)

 # Common configuration for all build modes.
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14")


Huh, I'm surprised we didn't already have this, but sure, makes sense.

I think this parameter is coming down from travis. Do we need to explicitly set it in cmake?

alexmalyshev · 2017-12-12T23:00:11Z

CMakeLists.txt

 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -pedantic")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Woverloaded-virtual")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g")

+# does the compiler support std::atomic_load(&std::shared_ptr<T>) ?
+try_compile(HAS_NATIVE_ATOMIC_SHARED_PTR ${CMAKE_BINARY_DIR}/has_shared_ptr_support_rs
+    ${CMAKE_CURRENT_SOURCE_DIR}/yarpl/test/test_has_shared_ptr_support.cpp)


You could use https://cmake.org/cmake/help/v3.0/module/CheckCXXSourceCompiles.html to write the C++ code inline here if you want. I wouldn't block the change on it though.

alexmalyshev · 2017-12-12T23:02:40Z

yarpl/include/yarpl/Refcounted.h


-class enable_get_ref {
+class enable_get_ref : public std::enable_shared_from_this<enable_get_ref> {


Why do we need this as opposed to good ol' fashioned std::enable_shared_from_this<T>? Is it because we need some base class to be the shared virtual class?

Yep, we just need something to be the inherited class (not even virtual).

alexmalyshev

Gonna bless this.

facebook-github-bot

@lexs has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

Summary: Manual import/rebase of #845 Reviewed By: lehecka Differential Revision: D6620084 fbshipit-source-id: ba3e44960c1cc18318767ca479e1e35449c0d51b

Summary: Manual import/rebase of rsocket/rsocket-cpp#845 Reviewed By: lehecka Differential Revision: D6620084 fbshipit-source-id: ba3e44960c1cc18318767ca479e1e35449c0d51b

dymk · 2018-01-03T22:01:56Z

Pulled in via b3f1927

dymk mentioned this pull request Dec 8, 2017

fix AtomicReference correctness #844

Closed

dymk changed the title ~~Remove custom Refcounted type~~ Replace Refcounted with std::shared_ptr Dec 8, 2017

dymk force-pushed the remove-refcounted branch 9 times, most recently from d4ea30b to 9451968 Compare December 11, 2017 22:40

dymk commented Dec 11, 2017

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lexs reviewed Dec 12, 2017

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alexmalyshev reviewed Dec 12, 2017

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alexmalyshev approved these changes Dec 12, 2017

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Dylan Knutson added 3 commits December 14, 2017 11:38

Remove custom Refcounted type

2d5807f

explicit null shared ptr object

7215aad

Detect compiler features for std::atomic<std::shared_ptr>>

35ed41a

dymk force-pushed the remove-refcounted branch from 9451968 to 35ed41a Compare December 14, 2017 19:42

facebook-github-bot reviewed Dec 15, 2017

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facebook-github-bot pushed a commit that referenced this pull request Jan 3, 2018

Replace Refcounted with std::shared_ptr

b3f1927

Summary: Manual import/rebase of #845 Reviewed By: lehecka Differential Revision: D6620084 fbshipit-source-id: ba3e44960c1cc18318767ca479e1e35449c0d51b

dymk closed this Jan 3, 2018

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		class enable_get_ref {
		class enable_get_ref : public std::enable_shared_from_this<enable_get_ref> {

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