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diff --git a/third_party/git/compat/nedmalloc/Readme.txt b/third_party/git/compat/nedmalloc/Readme.txt new file mode 100644 index 000000000000..07cbf50c0f9a --- /dev/null +++ b/third_party/git/compat/nedmalloc/Readme.txt @@ -0,0 +1,136 @@ +nedalloc v1.05 15th June 2008: +-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= + +by Niall Douglas (http://www.nedprod.com/programs/portable/nedmalloc/) + +Enclosed is nedalloc, an alternative malloc implementation for multiple +threads without lock contention based on dlmalloc v2.8.4. It is more +or less a newer implementation of ptmalloc2, the standard allocator in +Linux (which is based on dlmalloc v2.7.0) but also contains a per-thread +cache for maximum CPU scalability. + +It is licensed under the Boost Software License which basically means +you can do anything you like with it. This does not apply to the malloc.c.h +file which remains copyright to others. + +It has been tested on win32 (x86), win64 (x64), Linux (x64), FreeBSD (x64) +and Apple MacOS X (x86). It works very well on all of these and is very +significantly faster than the system allocator on all of these platforms. + +By literally dropping in this allocator as a replacement for your system +allocator, you can see real world improvements of up to three times in normal +code! + +To use: +-=-=-=- +Drop in nedmalloc.h, nedmalloc.c and malloc.c.h into your project. +Configure using the instructions in nedmalloc.h. Run and enjoy. + +To test, compile test.c. It will run a comparison between your system +allocator and nedalloc and tell you how much faster nedalloc is. It also +serves as an example of usage. + +Notes: +-=-=-= +If you want the very latest version of this allocator, get it from the +TnFOX SVN repository at svn://svn.berlios.de/viewcvs/tnfox/trunk/src/nedmalloc + +Because of how nedalloc allocates an mspace per thread, it can cause +severe bloating of memory usage under certain allocation patterns. +You can substantially reduce this wastage by setting MAXTHREADSINPOOL +or the threads parameter to nedcreatepool() to a fraction of the number of +threads which would normally be in a pool at once. This will reduce +bloating at the cost of an increase in lock contention. If allocated size +is less than THREADCACHEMAX, locking is avoided 90-99% of the time and +if most of your allocations are below this value, you can safely set +MAXTHREADSINPOOL to one. + +You will suffer memory leakage unless you call neddisablethreadcache() +per pool for every thread which exits. This is because nedalloc cannot +portably know when a thread exits and thus when its thread cache can +be returned for use by other code. Don't forget pool zero, the system pool. + +For C++ type allocation patterns (where the same sizes of memory are +regularly allocated and deallocated as objects are created and destroyed), +the threadcache always benefits performance. If however your allocation +patterns are different, searching the threadcache may significantly slow +down your code - as a rule of thumb, if cache utilisation is below 80% +(see the source for neddisablethreadcache() for how to enable debug +printing in release mode) then you should disable the thread cache for +that thread. You can compile out the threadcache code by setting +THREADCACHEMAX to zero. + +Speed comparisons: +-=-=-=-=-=-=-=-=-= +See Benchmarks.xls for details. + +The enclosed test.c can do two things: it can be a torture test or a speed +test. The speed test is designed to be a representative synthetic +memory allocator test. It works by randomly mixing allocations with frees +with half of the allocation sizes being a two power multiple less than +512 bytes (to mimic C++ stack instantiated objects) and the other half +being a simple random value less than 16Kb. + +The real world code results are from Tn's TestIO benchmark. This is a +heavily multithreaded and memory intensive benchmark with a lot of branching +and other stuff modern processors don't like so much. As you'll note, the +test doesn't show the benefits of the threadcache mostly due to the saturation +of the memory bus being the limiting factor. + +ChangeLog: +-=-=-=-=-= +v1.05 15th June 2008: + * { 1042 } Added error check for TLSSET() and TLSFREE() macros. Thanks to +Markus Elfring for reporting this. + * { 1043 } Fixed a segfault when freeing memory allocated using +nedindependent_comalloc(). Thanks to Pavel Vozenilek for reporting this. + +v1.04 14th July 2007: + * Fixed a bug with the new optimised implementation that failed to lock +on a realloc under certain conditions. + * Fixed lack of thread synchronisation in InitPool() causing pool corruption + * Fixed a memory leak of thread cache contents on disabling. Thanks to Earl +Chew for reporting this. + * Added a sanity check for freed blocks being valid. + * Reworked test.c into being a torture test. + * Fixed GCC assembler optimisation misspecification + +v1.04alpha_svn915 7th October 2006: + * Fixed failure to unlock thread cache list if allocating a new list failed. +Thanks to Dmitry Chichkov for reporting this. Further thanks to Aleksey Sanin. + * Fixed realloc(0, <size>) segfaulting. Thanks to Dmitry Chichkov for +reporting this. + * Made config defines #ifndef so they can be overridden by the build system. +Thanks to Aleksey Sanin for suggesting this. + * Fixed deadlock in nedprealloc() due to unnecessary locking of preferred +thread mspace when mspace_realloc() always uses the original block's mspace +anyway. Thanks to Aleksey Sanin for reporting this. + * Made some speed improvements by hacking mspace_malloc() to no longer lock +its mspace, thus allowing the recursive mutex implementation to be removed +with an associated speed increase. Thanks to Aleksey Sanin for suggesting this. + * Fixed a bug where allocating mspaces overran its max limit. Thanks to +Aleksey Sanin for reporting this. + +v1.03 10th July 2006: + * Fixed memory corruption bug in threadcache code which only appeared with >4 +threads and in heavy use of the threadcache. + +v1.02 15th May 2006: + * Integrated dlmalloc v2.8.4, fixing the win32 memory release problem and +improving performance still further. Speed is now up to twice the speed of v1.01 +(average is 67% faster). + * Fixed win32 critical section implementation. Thanks to Pavel Kuznetsov +for reporting this. + * Wasn't locking mspace if all mspaces were locked. Thanks to Pavel Kuznetsov +for reporting this. + * Added Apple Mac OS X support. + +v1.01 24th February 2006: + * Fixed multiprocessor scaling problems by removing sources of cache sloshing + * Earl Chew <earl_chew <at> agilent <dot> com> sent patches for the following: + 1. size2binidx() wasn't working for default code path (non x86) + 2. Fixed failure to release mspace lock under certain circumstances which + caused a deadlock + +v1.00 1st January 2006: + * First release |