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Posted to issues@stdcxx.apache.org by "Martin Sebor (JIRA)" <ji...@apache.org> on 2008/05/07 06:21:55 UTC
[jira] Commented: (STDCXX-914) sstream ctors inefficient in
reentrant modes
[ https://issues.apache.org/jira/browse/STDCXX-914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12594770#action_12594770 ]
Martin Sebor commented on STDCXX-914:
-------------------------------------
gprof flat profile for a 15D build with gcc 4.3.0 on x86_64:
\\
{noformat}
Flat profile:
Each sample counts as 0.01 seconds.
% cumulative self self total
time seconds seconds calls ns/call ns/call name
33.40 0.08 0.08 1000000 80.15 200.37 std::string lex_cast<std::string, long>(long const&)
16.70 0.12 0.04 1000000 40.07 90.17 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream()
16.70 0.16 0.04 main
12.52 0.19 0.03 1000000 30.06 40.07 std::basic_iostream<char, std::char_traits<char> >::~basic_iostream()
8.35 0.21 0.02 1000000 20.04 20.04 std::basic_iostream<char, std::char_traits<char> >::basic_iostream(std::basic_streambuf<char, std::char_traits<char> >*)
4.17 0.22 0.01 1000000 10.02 10.02 std::basic_ostream<char, std::char_traits<char> >::~basic_ostream()
4.17 0.23 0.01 1000000 10.02 30.06 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode)
4.17 0.24 0.01 1000000 10.02 10.02 std::basic_ios<char, std::char_traits<char> >::~basic_ios()
0.00 0.24 0.00 14000002 0.00 0.00 data_start
0.00 0.24 0.00 1000001 0.00 0.00 std::allocator<char>::allocator()
0.00 0.24 0.00 1000000 0.00 0.00 __rw::__string_ref<char, std::char_traits<char>, std::allocator<char> >::~__string_ref()
0.00 0.24 0.00 1000000 0.00 0.00 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::rdbuf() const
0.00 0.24 0.00 1000000 0.00 0.00 std::basic_istream<char, std::char_traits<char> >::~basic_istream()
{noformat}
gprof call graph:
{noformat}
granularity: each sample hit covers 2 byte(s) for 4.16% of 0.24 seconds
index % time self children called name
<spontaneous>
[1] 100.0 0.04 0.20 main [1]
0.08 0.12 1000000/1000000 std::string lex_cast<std::string, long>(long const&) [2]
0.00 0.00 3000002/14000002 data_start [9]
0.00 0.00 1/1000001 std::allocator<char>::allocator() [15]
-----------------------------------------------
0.08 0.12 1000000/1000000 main [1]
[2] 83.3 0.08 0.12 1000000 std::string lex_cast<std::string, long>(long const&) [2]
0.04 0.05 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream() [3]
0.01 0.02 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode) [5]
0.00 0.00 5000000/14000002 data_start [9]
0.00 0.00 1000000/1000001 std::allocator<char>::allocator() [15]
-----------------------------------------------
0.04 0.05 1000000/1000000 std::string lex_cast<std::string, long>(long const&) [2]
[3] 37.5 0.04 0.05 1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream() [3]
0.03 0.01 1000000/1000000 std::basic_iostream<char, std::char_traits<char> >::~basic_iostream() [4]
0.01 0.00 1000000/1000000 std::basic_ios<char, std::char_traits<char> >::~basic_ios() [8]
0.00 0.00 1000000/14000002 data_start [9]
-----------------------------------------------
0.03 0.01 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream() [3]
[4] 16.7 0.03 0.01 1000000 std::basic_iostream<char, std::char_traits<char> >::~basic_iostream() [4]
0.01 0.00 1000000/1000000 std::basic_ostream<char, std::char_traits<char> >::~basic_ostream() [7]
0.00 0.00 1000000/1000000 std::basic_istream<char, std::char_traits<char> >::~basic_istream() [18]
-----------------------------------------------
0.01 0.02 1000000/1000000 std::string lex_cast<std::string, long>(long const&) [2]
[5] 12.5 0.01 0.02 1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode) [5]
0.02 0.00 1000000/1000000 std::basic_iostream<char, std::char_traits<char> >::basic_iostream(std::basic_streambuf<char, std::char_traits<char> >*) [6]
0.00 0.00 2000000/14000002 data_start [9]
0.00 0.00 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::rdbuf() const [17]
-----------------------------------------------
0.02 0.00 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode) [5]
[6] 8.3 0.02 0.00 1000000 std::basic_iostream<char, std::char_traits<char> >::basic_iostream(std::basic_streambuf<char, std::char_traits<char> >*) [6]
0.00 0.00 2000000/14000002 data_start [9]
-----------------------------------------------
0.01 0.00 1000000/1000000 std::basic_iostream<char, std::char_traits<char> >::~basic_iostream() [4]
[7] 4.2 0.01 0.00 1000000 std::basic_ostream<char, std::char_traits<char> >::~basic_ostream() [7]
-----------------------------------------------
0.01 0.00 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream() [3]
[8] 4.2 0.01 0.00 1000000 std::basic_ios<char, std::char_traits<char> >::~basic_ios() [8]
0.00 0.00 1000000/14000002 data_start [9]
-----------------------------------------------
0.00 0.00 1000000/14000002 std::basic_ios<char, std::char_traits<char> >::~basic_ios() [8]
0.00 0.00 1000000/14000002 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream() [3]
0.00 0.00 2000000/14000002 std::basic_iostream<char, std::char_traits<char> >::basic_iostream(std::basic_streambuf<char, std::char_traits<char> >*) [6]
0.00 0.00 2000000/14000002 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode) [5]
0.00 0.00 3000002/14000002 main [1]
0.00 0.00 5000000/14000002 std::string lex_cast<std::string, long>(long const&) [2]
[9] 0.0 0.00 0.00 14000002 data_start [9]
-----------------------------------------------
0.00 0.00 1/1000001 main [1]
0.00 0.00 1000000/1000001 std::string lex_cast<std::string, long>(long const&) [2]
[15] 0.0 0.00 0.00 1000001 std::allocator<char>::allocator() [15]
-----------------------------------------------
0.00 0.00 1000000/1000000 std::allocator<__rw::__string_ref<char, std::char_traits<char>, std::allocator<char> > >::destroy(__rw::__string_ref<char, std::char_traits<char>, std::allocator<char> >*) [19]
[16] 0.0 0.00 0.00 1000000 __rw::__string_ref<char, std::char_traits<char>, std::allocator<char> >::~__string_ref() [16]
-----------------------------------------------
0.00 0.00 1000000/1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode) [5]
[17] 0.0 0.00 0.00 1000000 std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::rdbuf() const [17]
-----------------------------------------------
0.00 0.00 1000000/1000000 std::basic_iostream<char, std::char_traits<char> >::~basic_iostream() [4]
[18] 0.0 0.00 0.00 1000000 std::basic_istream<char, std::char_traits<char> >::~basic_istream() [18]
-----------------------------------------------
{noformat}
and index by function name:
{noformat}
[2] std::string lex_cast<std::string, long>(long const&) [4] std::basic_iostream<char, std::char_traits<char> >::~basic_iostream() [8] std::basic_ios<char, std::char_traits<char> >::~basic_ios()
[16] __rw::__string_ref<char, std::char_traits<char>, std::allocator<char> >::~__string_ref() [18] std::basic_istream<char, std::char_traits<char> >::~basic_istream() [9] data_start
[17] std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::rdbuf() const [7] std::basic_ostream<char, std::char_traits<char> >::~basic_ostream() [1] main
[15] std::allocator<char>::allocator() [5] std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(__rw::__rw_openmode)
[6] std::basic_iostream<char, std::char_traits<char> >::basic_iostream(std::basic_streambuf<char, std::char_traits<char> >*) [3] std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::~basic_stringstream()
{noformat}
> sstream ctors inefficient in reentrant modes
> --------------------------------------------
>
> Key: STDCXX-914
> URL: https://issues.apache.org/jira/browse/STDCXX-914
> Project: C++ Standard Library
> Issue Type: Improvement
> Components: 27. Input/Output
> Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0, 4.2.1
> Reporter: Martin Sebor
> Priority: Critical
> Fix For: 4.2.2
>
> Original Estimate: 12h
> Remaining Estimate: 12h
>
> As discussed in this [thread|http://markmail.org/message/hqlsw5dq23gx7d4o] stream ctors in thread-safe builds are inefficient due to the initialization of the mutex data member in every stream, even in those that never use it. As soon as binary compatibility rules permit it we should remove the mutex and/or defer its initialization until it's needed. It might be possible to implement the deferred initialization as early as 4.2.2, or maybe 4.3. Complete removal will need to wait until 5.0.
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