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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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