[Bug libstdc++/42381] New: deque shouldn't reserve that much memory

[Bug libstdc++/42381] New: deque shouldn't reserve that much memory

[kraemer at informatik dot uni-kl dot de]

In bits/stl_deque.h, line 80ff the minimal allocated size is set fixed to 512.
This should be configurable, at least via a macro.
In case of small memory systems (embedded devices) resveration of this amount
of memory is much too high.


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           Summary: deque shouldn't reserve that much memory
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: kraemer at informatik dot uni-kl dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381

[Bug libstdc++/42381] deque shouldn't reserve that much memory

[paolo dot carlini at oracle dot com]

------- Comment #1 from paolo dot carlini at oracle dot com  2009-12-15 17:38 -------
Changing the value, via macro or whatever is trivial, and I can tell you for
sure from some experiment I did, that a *larger* value is much better, when
memory is available, for operations like copies. Changing the value however,
breaks the binary compatibility between objects (e.g, one allocating, the other
deallocating the same deque), it's a dangerous option.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381

[Bug libstdc++/42381] deque shouldn't reserve that much memory

[paolo dot carlini at oracle dot com]

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paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381

[Bug libstdc++/42381] deque shouldn't reserve that much memory

[paolo dot carlini at oracle dot com]

------- Comment #2 from paolo dot carlini at oracle dot com  2009-12-15 17:57 -------
Let's add a macro (with a *big* warning), will be also useful for experimenting
when I will add (soon) the segmented iterator optimization for copies.


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paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |paolo dot carlini at oracle
                   |dot org                     |dot com
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2009-12-15 17:57:38
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381

[Bug libstdc++/42381] deque shouldn't reserve that much memory

[paolo at gcc dot gnu dot org]

------- Comment #3 from paolo at gcc dot gnu dot org  2009-12-15 20:58 -------
Subject: Bug 42381

Author: paolo
Date: Tue Dec 15 20:58:29 2009
New Revision: 155271

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=155271
Log:
2009-12-15  Paolo Carlini  <paolo.carlini@oracle.com>

        PR libsdtc++/42381
        * include/bits/stl_deque.h (_GLIBCXX_DEQUE_BUF_SIZE): Add.
        (__deque_buf_size(size_t)): Use it.
        * testsuite/23_containers/deque/requirements/dr438/
        assign_neg.cc: Adjust dg-error line numbers.
        * testsuite/23_containers/deque/requirements/dr438/
        insert_neg.cc: Likewise.
        * testsuite/23_containers/deque/requirements/dr438/
        constructor_1_neg.cc: Likewise.
        * testsuite/23_containers/deque/requirements/dr438/
        constructor_2_neg.cc: Likewise.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/stl_deque.h
   
trunk/libstdc++-v3/testsuite/23_containers/deque/requirements/dr438/assign_neg.cc
   
trunk/libstdc++-v3/testsuite/23_containers/deque/requirements/dr438/constructor_1_neg.cc
   
trunk/libstdc++-v3/testsuite/23_containers/deque/requirements/dr438/constructor_2_neg.cc
   
trunk/libstdc++-v3/testsuite/23_containers/deque/requirements/dr438/insert_neg.cc


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381

[Bug libstdc++/42381] deque shouldn't reserve that much memory

[paolo dot carlini at oracle dot com]

------- Comment #4 from paolo dot carlini at oracle dot com  2009-12-15 21:01 -------
Done.


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paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381

[Bug libstdc++/42381] deque shouldn't reserve that much memory

[kraemer at informatik dot uni-kl dot de]

------- Comment #5 from kraemer at informatik dot uni-kl dot de  2009-12-16 10:50 -------
thanks a lot.
in our scenario it showed 8 buckets to be the best. but this may vary by usage.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42381