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Signed-off-by: Ondřej Bílka <neleai@seznam.cz> Signed-off-by: Junio C Hamano <gitster@pobox.com>
136 lines
6.3 KiB
Text
136 lines
6.3 KiB
Text
nedalloc v1.05 15th June 2008:
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-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
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by Niall Douglas (http://www.nedprod.com/programs/portable/nedmalloc/)
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Enclosed is nedalloc, an alternative malloc implementation for multiple
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threads without lock contention based on dlmalloc v2.8.4. It is more
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or less a newer implementation of ptmalloc2, the standard allocator in
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Linux (which is based on dlmalloc v2.7.0) but also contains a per-thread
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cache for maximum CPU scalability.
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It is licensed under the Boost Software License which basically means
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you can do anything you like with it. This does not apply to the malloc.c.h
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file which remains copyright to others.
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It has been tested on win32 (x86), win64 (x64), Linux (x64), FreeBSD (x64)
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and Apple MacOS X (x86). It works very well on all of these and is very
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significantly faster than the system allocator on all of these platforms.
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By literally dropping in this allocator as a replacement for your system
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allocator, you can see real world improvements of up to three times in normal
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code!
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To use:
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-=-=-=-
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Drop in nedmalloc.h, nedmalloc.c and malloc.c.h into your project.
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Configure using the instructions in nedmalloc.h. Run and enjoy.
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To test, compile test.c. It will run a comparison between your system
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allocator and nedalloc and tell you how much faster nedalloc is. It also
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serves as an example of usage.
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Notes:
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-=-=-=
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If you want the very latest version of this allocator, get it from the
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TnFOX SVN repository at svn://svn.berlios.de/viewcvs/tnfox/trunk/src/nedmalloc
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Because of how nedalloc allocates an mspace per thread, it can cause
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severe bloating of memory usage under certain allocation patterns.
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You can substantially reduce this wastage by setting MAXTHREADSINPOOL
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or the threads parameter to nedcreatepool() to a fraction of the number of
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threads which would normally be in a pool at once. This will reduce
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bloating at the cost of an increase in lock contention. If allocated size
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is less than THREADCACHEMAX, locking is avoided 90-99% of the time and
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if most of your allocations are below this value, you can safely set
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MAXTHREADSINPOOL to one.
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You will suffer memory leakage unless you call neddisablethreadcache()
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per pool for every thread which exits. This is because nedalloc cannot
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portably know when a thread exits and thus when its thread cache can
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be returned for use by other code. Don't forget pool zero, the system pool.
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For C++ type allocation patterns (where the same sizes of memory are
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regularly allocated and deallocated as objects are created and destroyed),
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the threadcache always benefits performance. If however your allocation
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patterns are different, searching the threadcache may significantly slow
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down your code - as a rule of thumb, if cache utilisation is below 80%
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(see the source for neddisablethreadcache() for how to enable debug
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printing in release mode) then you should disable the thread cache for
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that thread. You can compile out the threadcache code by setting
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THREADCACHEMAX to zero.
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Speed comparisons:
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-=-=-=-=-=-=-=-=-=
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See Benchmarks.xls for details.
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The enclosed test.c can do two things: it can be a torture test or a speed
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test. The speed test is designed to be a representative synthetic
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memory allocator test. It works by randomly mixing allocations with frees
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with half of the allocation sizes being a two power multiple less than
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512 bytes (to mimic C++ stack instantiated objects) and the other half
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being a simple random value less than 16Kb.
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The real world code results are from Tn's TestIO benchmark. This is a
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heavily multithreaded and memory intensive benchmark with a lot of branching
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and other stuff modern processors don't like so much. As you'll note, the
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test doesn't show the benefits of the threadcache mostly due to the saturation
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of the memory bus being the limiting factor.
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ChangeLog:
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-=-=-=-=-=
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v1.05 15th June 2008:
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* { 1042 } Added error check for TLSSET() and TLSFREE() macros. Thanks to
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Markus Elfring for reporting this.
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* { 1043 } Fixed a segfault when freeing memory allocated using
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nedindependent_comalloc(). Thanks to Pavel Vozenilek for reporting this.
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v1.04 14th July 2007:
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* Fixed a bug with the new optimised implementation that failed to lock
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on a realloc under certain conditions.
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* Fixed lack of thread synchronisation in InitPool() causing pool corruption
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* Fixed a memory leak of thread cache contents on disabling. Thanks to Earl
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Chew for reporting this.
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* Added a sanity check for freed blocks being valid.
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* Reworked test.c into being a torture test.
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* Fixed GCC assembler optimisation misspecification
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v1.04alpha_svn915 7th October 2006:
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* Fixed failure to unlock thread cache list if allocating a new list failed.
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Thanks to Dmitry Chichkov for reporting this. Further thanks to Aleksey Sanin.
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* Fixed realloc(0, <size>) segfaulting. Thanks to Dmitry Chichkov for
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reporting this.
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* Made config defines #ifndef so they can be overridden by the build system.
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Thanks to Aleksey Sanin for suggesting this.
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* Fixed deadlock in nedprealloc() due to unnecessary locking of preferred
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thread mspace when mspace_realloc() always uses the original block's mspace
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anyway. Thanks to Aleksey Sanin for reporting this.
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* Made some speed improvements by hacking mspace_malloc() to no longer lock
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its mspace, thus allowing the recursive mutex implementation to be removed
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with an associated speed increase. Thanks to Aleksey Sanin for suggesting this.
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* Fixed a bug where allocating mspaces overran its max limit. Thanks to
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Aleksey Sanin for reporting this.
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v1.03 10th July 2006:
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* Fixed memory corruption bug in threadcache code which only appeared with >4
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threads and in heavy use of the threadcache.
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v1.02 15th May 2006:
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* Integrated dlmalloc v2.8.4, fixing the win32 memory release problem and
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improving performance still further. Speed is now up to twice the speed of v1.01
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(average is 67% faster).
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* Fixed win32 critical section implementation. Thanks to Pavel Kuznetsov
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for reporting this.
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* Wasn't locking mspace if all mspaces were locked. Thanks to Pavel Kuznetsov
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for reporting this.
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* Added Apple Mac OS X support.
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v1.01 24th February 2006:
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* Fixed multiprocessor scaling problems by removing sources of cache sloshing
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* Earl Chew <earl_chew <at> agilent <dot> com> sent patches for the following:
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1. size2binidx() wasn't working for default code path (non x86)
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2. Fixed failure to release mspace lock under certain circumstances which
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caused a deadlock
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v1.00 1st January 2006:
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* First release
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