[Boost-bugs] [Boost C++ Libraries] #1252: [pool] severe overhead with unaligned sizes.

Subject: [Boost-bugs] [Boost C++ Libraries] #1252: [pool] severe overhead with unaligned sizes.
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2007-09-12 21:05:40

#1252: [pool] severe overhead with unaligned sizes.
-------------------------------+--------------------------------------------
 Reporter:  phrosty_at_[hidden]  |        Type:  Bugs        
   Status:  new                |   Milestone:  Boost 1.35.0
Component:  None               |     Version:  Boost 1.34.1
 Severity:  Problem            |    Keywords:  pool        
-------------------------------+--------------------------------------------
 Pool will set the size of allocated blocks to the least common multiple of
 the requested size and LCM(sizeof(void*), sizeof(size_t)).

 Request a block size of 1500 on a 32-bit system and you get 1500 byte
 blocks.  Request 1501 bytes and you get 6004 byte blocks - and the extra
 space isn't ever used.  It is obviously even more pronounced on a 64-bit
 system.

 I believe the intent of the author was to align block sizes, not to use
 LCM.  I propose changing pool.hpp:183 from

 `return details::pool::lcm<size_type>(requested_size, min_size);`

 to

 `return requested_size + (min_size - 1) & ~(min_size - 1);`

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/1252>
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