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@ -1235,18 +1235,7 @@ HTML_EXTRA_STYLESHEET = mimalloc-doxygen.css
# files will be copied as-is; there are no commands or markers available. # files will be copied as-is; there are no commands or markers available.
# This tag requires that the tag GENERATE_HTML is set to YES. # This tag requires that the tag GENERATE_HTML is set to YES.
HTML_EXTRA_FILES = bench-r5a-4xlarge-t1.png \ HTML_EXTRA_FILES =
bench-r5a-4xlarge-t2.png \
bench-r5a-4xlarge-m1.png \
bench-r5a-4xlarge-m2.png \
bench-c5d-2xlarge-t1.png \
bench-c5d-2xlarge-t2.png \
bench-c5d-2xlarge-m1.png \
bench-c5d-2xlarge-m2.png \
bench-z4-win-t1.png \
bench-z4-win-t2.png \
bench-z4-win-m1.png \
bench-z4-win-m2.png
# The HTML_COLORSTYLE_HUE tag controls the color of the HTML output. Doxygen # The HTML_COLORSTYLE_HUE tag controls the color of the HTML output. Doxygen
# will adjust the colors in the style sheet and background images according to # will adjust the colors in the style sheet and background images according to

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doc/mimalloc-doc.h
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@ -11,13 +11,19 @@ terms of the MIT license. A copy of the license can be found in the file
/*! \mainpage /*! \mainpage
This is the API documentation of the This is the API documentation of the
[mimalloc](https://github.com/koka-lang/mimalloc) allocator [mimalloc](https://github.com/microsoft/mimalloc) allocator
(pronounced "me-malloc") -- a (pronounced "me-malloc") -- a
general purpose allocator with excellent [performance](bench.html) general purpose allocator with excellent [performance](bench.html)
characteristics. Initially characteristics. Initially
developed by Daan Leijen for the run-time systems of the developed by Daan Leijen for the run-time systems of the
[Koka](https://github.com/koka-lang/koka) and [Lean](https://github.com/leanprover/lean) languages. [Koka](https://github.com/koka-lang/koka) and [Lean](https://github.com/leanprover/lean) languages.
It is a drop-in replacement for `malloc` and can be used in other programs
without code changes, for example, on Unix you can use it as:
```
> LD_PRELOAD=/usr/bin/libmimalloc.so myprogram
```
Notable aspects of the design include: Notable aspects of the design include:
- __small and consistent__: the library is less than 3500 LOC using simple and - __small and consistent__: the library is less than 3500 LOC using simple and
@ -25,23 +31,32 @@ Notable aspects of the design include:
to integrate and adapt in other projects. For runtime systems it to integrate and adapt in other projects. For runtime systems it
provides hooks for a monotonic _heartbeat_ and deferred freeing (for provides hooks for a monotonic _heartbeat_ and deferred freeing (for
bounded worst-case times with reference counting). bounded worst-case times with reference counting).
- __free list sharding__: "the big idea": instead of one big free list (per size class) we have - __free list sharding__: the big idea: instead of one big free list (per size class) we have
many smaller lists per memory "page" which both reduces fragmentation many smaller lists per memory "page" which both reduces fragmentation
and increases locality -- and increases locality --
things that are allocated close in time get allocated close in memory. things that are allocated close in time get allocated close in memory.
(A memory "page" in mimalloc contains blocks of one size class and is (A memory "page" in _mimalloc_ contains blocks of one size class and is
usually 64KB on a 64-bit system). usually 64KiB on a 64-bit system).
- __eager page reset__: when a "page" becomes empty (with increased chance - __eager page reset__: when a "page" becomes empty (with increased chance
due to free list sharding) the memory is marked to the OS as unused ("reset" or "purged") due to free list sharding) the memory is marked to the OS as unused ("reset" or "purged")
reducing (real) memory pressure and fragmentation, especially in long running reducing (real) memory pressure and fragmentation, especially in long running
programs. programs.
- __lazy initialization__: pages in a segment are lazily initialized so - __secure__: _mimalloc_ can be build in secure mode, adding guard pages,
no memory is touched until it becomes allocated, reducing the resident randomized allocation, encrypted free lists, etc. to protect against various
memory and potential page faults. heap vulnerabilities. The performance penalty is only around 3% on average
over our benchmarks.
- __first-class heaps__: efficiently create and use multiple heaps to allocate across different regions.
A heap can be destroyed at once instead of deallocating each object separately.
- __bounded__: it does not suffer from _blowup_ \[1\], has bounded worst-case allocation - __bounded__: it does not suffer from _blowup_ \[1\], has bounded worst-case allocation
times (_wcat_), bounded space overhead (~0.2% meta-data, with at most 16.7% waste in allocation sizes), times (_wcat_), bounded space overhead (~0.2% meta-data, with at most 16.7% waste in allocation sizes),
and has no internal points of contention using atomic operations almost and has no internal points of contention using only atomic operations.
everywhere. - __fast__: In our benchmarks (see [below](#performance)),
_mimalloc_ always outperforms all other leading allocators (_jemalloc_, _tcmalloc_, _Hoard_, etc),
and usually uses less memory (up to 25% more in the worst case). A nice property
is that it does consistently well over a wide range of benchmarks.
You can read more on the design of _mimalloc_ in the upcoming technical report
which also has detailed benchmark results.
Further information: Further information:
@ -623,13 +638,13 @@ void mi_option_set_default(mi_option_t option, long value);
Checkout the sources from Github: Checkout the sources from Github:
``` ```
git clone https://github.com/koka-lang/mimalloc.git git clone https://github.com/microsoft/mimalloc
``` ```
## Windows ## Windows
Open `ide/vs2017/mimalloc.sln` in Visual Studio 2017 and build. Open `ide/vs2017/mimalloc.sln` in Visual Studio 2017 and build.
The `mimalloc` project builds a static library, while the The `mimalloc` project builds a static library (in `out/msvc-x64`), while the
`mimalloc-override` project builds a DLL for overriding malloc `mimalloc-override` project builds a DLL for overriding malloc
in the entire program. in the entire program.
@ -637,44 +652,50 @@ in the entire program.
We use [`cmake`](https://cmake.org)<sup>1</sup> as the build system: We use [`cmake`](https://cmake.org)<sup>1</sup> as the build system:
- `mkdir -p out/release` (create a build directory) ```
- `cd out/release` (go to it) > mkdir -p out/release
- `cmake ../..` (generate the make file) > cd out/release
- `make` (and build) > cmake ../..
> make
This will build the library as a shared (dynamic) ```
This builds the library as a shared (dynamic)
library (`.so` or `.dylib`), a static library (`.a`), and library (`.so` or `.dylib`), a static library (`.a`), and
as a single object file (`.o`). as a single object file (`.o`).
- `sudo make install` (install the library and header files in `/usr/lib` and `/usr/include`) `> sudo make install` (install the library and header files in `/usr/local/lib` and `/usr/local/include`)
Use the option `-DCMAKE_INSTALL_PREFIX=../local` (for example) to the `ccmake`
command to install to a local directory to see what gets installed.
You can build the debug version which does many internal checks and You can build the debug version which does many internal checks and
maintains detailed statistics as: maintains detailed statistics as:
- `mkdir -p out/debug` ```
- `cd out/debug` > mkdir -p out/debug
- `cmake -DCMAKE_BUILD_TYPE=Debug ../..` > cd out/debug
- `make` > cmake -DCMAKE_BUILD_TYPE=Debug ../..
> make
```
This will name the shared library as `libmimalloc-debug.so`. This will name the shared library as `libmimalloc-debug.so`.
Or build with `clang`: Finally, you can build a _secure_ version that uses guard pages, encrypted
free lists, etc, as:
- `CC=clang cmake ../..` ```
> mkdir -p out/secure
> cd out/secure
> cmake -DSECURE=ON ../..
> make
```
This will name the shared library as `libmimalloc-secure.so`.
Use `ccmake`<sup>2</sup> instead of `cmake` Use `ccmake`<sup>2</sup> instead of `cmake`
to see and customize all the available build options. to see and customize all the available build options.
Notes: Notes:
1. Install CMake: `sudo apt-get install cmake` 1. Install CMake: `sudo apt-get install cmake`
2. Install CCMake: `sudo apt-get install cmake-curses-gui` 2. Install CCMake: `sudo apt-get install cmake-curses-gui`
*/ */
/*! \page using Using the library /*! \page using Using the library
The preferred usage is including `<mimalloc.h>`, linking with The preferred usage is including `<mimalloc.h>`, linking with
the shared- or static library, and using the `mi_malloc` API exclusively for allocation. For example, the shared- or static library, and using the `mi_malloc` API exclusively for allocation. For example,
``` ```
@ -745,7 +766,7 @@ See \ref overrides for more info.
/*! \page overrides Overriding Malloc /*! \page overrides Overriding Malloc
Overriding standard malloc can be done either _dynamically_ or _statically_. Overriding the standard `malloc` can be done either _dynamically_ or _statically_.
## Dynamic override ## Dynamic override
@ -753,7 +774,7 @@ This is the recommended way to override the standard malloc interface.
### Unix, BSD, MacOSX ### Unix, BSD, MacOSX
On these system we preload the mimalloc shared On these systems we preload the mimalloc shared
library so all calls to the standard `malloc` interface are library so all calls to the standard `malloc` interface are
resolved to the _mimalloc_ library. resolved to the _mimalloc_ library.
@ -770,7 +791,7 @@ env MIMALLOC_VERBOSE=1 LD_PRELOAD=/usr/lib/libmimalloc.so myprogram
``` ```
or run with the debug version to get detailed statistics: or run with the debug version to get detailed statistics:
``` ```
env MIMALLOC_STATS=1 LD_PRELOAD=/usr/lib/libmimallocd.so myprogram env MIMALLOC_STATS=1 LD_PRELOAD=/usr/lib/libmimalloc-debug.so myprogram
``` ```
### Windows ### Windows
@ -780,7 +801,7 @@ DLL, and use the C-runtime library as a DLL (the `/MD` or `/MDd` switch).
To ensure the mimalloc DLL gets loaded it is easiest to insert some To ensure the mimalloc DLL gets loaded it is easiest to insert some
call to the mimalloc API in the `main` function, like `mi_version()`. call to the mimalloc API in the `main` function, like `mi_version()`.
Due to the way mimalloc overrides the standard malloc at runtime, it is best Due to the way mimalloc intercepts the standard malloc at runtime, it is best
to link to the mimalloc import library first on the command line so it gets to link to the mimalloc import library first on the command line so it gets
loaded right after the universal C runtime DLL (`ucrtbase`). See loaded right after the universal C runtime DLL (`ucrtbase`). See
the `mimalloc-override-test` project for an example. the `mimalloc-override-test` project for an example.
@ -788,9 +809,9 @@ the `mimalloc-override-test` project for an example.
## Static override ## Static override
You can also statically link with _mimalloc_ to override the standard On Unix systems, you can also statically link with _mimalloc_ to override the standard
malloc interface. The recommended way is to link the final program with the malloc interface. The recommended way is to link the final program with the
_mimalloc_ single object file (`mimalloc-override.o` (or `.obj`)). We use _mimalloc_ single object file (`mimalloc-override.o`). We use
an object file instead of a library file as linkers give preference to an object file instead of a library file as linkers give preference to
that over archives to resolve symbols. To ensure that the standard that over archives to resolve symbols. To ensure that the standard
malloc interface resolves to the _mimalloc_ library, link it as the first malloc interface resolves to the _mimalloc_ library, link it as the first
@ -858,239 +879,19 @@ void _free_dbg(void* p, int block_type);
/*! \page bench Performance /*! \page bench Performance
We tested _mimalloc_ against many other top allocators over a wide
range of benchmarks, ranging from various real world programs to
synthetic benchmarks that see how the allocator behaves under more
extreme circumstances.
tldr: In our benchmarks, mimalloc always outperforms In our benchmarks, _mimalloc_ always outperforms all other leading
all other leading allocators (jemalloc, tcmalloc, hoard, and glibc), and usually allocators (_jemalloc_, _tcmalloc_, _Hoard_, etc) (Apr 2019),
uses less memory (with less then 25% more in the worst case) (as of Jan 2019). and usually uses less memory (up to 25% more in the worst case).
A nice property is that it does consistently well over a wide range of benchmarks. A nice property is that it does *consistently* well over the wide
range of benchmarks.
Disclaimer: allocators are interesting as there is no optimal algorithm -- for See the [Performance](https://github.com/microsoft/mimalloc#Performance)
a given allocator one can always construct a workload where it does not do so well. section in the _mimalloc_ repository for benchmark results,
The goal is thus to find an allocation strategy that performs well over a wide or the the technical report for detailed benchmark results.
range of benchmarks without suffering from underperformance in less
common situations (which is what our second benchmark set tests for).
## Benchmarking
We tested _mimalloc_ with 5 other allocators over 11 benchmarks.
The tested allocators are:
- **mi**: The mimalloc allocator (version tag `v1.0.0`).
- **je**: [jemalloc](https://github.com/jemalloc/jemalloc), by [Jason Evans](https://www.facebook.com/notes/facebook-engineering/scalable-memory-allocation-using-jemalloc/480222803919) (Facebook);
currently (2018) one of the leading allocators and is widely used, for example
in BSD, Firefox, and at Facebook. Installed as package `libjemalloc-dev:amd64/bionic 3.6.0-11`.
- **tc**: [tcmalloc](https://github.com/gperftools/gperftools), by Google as part of the performance tools.
Highly performant and used in the Chrome browser. Installed as package `libgoogle-perftools-dev:amd64/bionic 2.5-2.2ubuntu3`.
- **jx**: A compiled version of a more recent instance of [jemalloc](https://github.com/jemalloc/jemalloc).
Using commit ` 7a815c1b` ([dev](https://github.com/jemalloc/jemalloc/tree/dev), 2019-01-15).
- **hd**: [Hoard](https://github.com/emeryberger/Hoard), by Emery Berger \[1].
One of the first multi-thread scalable allocators.
([master](https://github.com/emeryberger/Hoard), 2019-01-01, version tag `3.13`)
- **mc**: The system allocator. Here we use the LibC allocator (which is originally based on
PtMalloc). Using version 2.27. (Note that version 2.26 significantly improved scalability over
earlier versions).
All allocators run exactly the same benchmark programs and use `LD_PRELOAD` to override the system allocator.
The wall-clock elapsed time and peak resident memory (_rss_) are
measured with the `time` program. The best scores over 5 runs are used.
Performance is reported relative to mimalloc, e.g. a time of 66% means that
mimalloc ran 1.5&times; faster (i.e. that mimalloc finished in 66% of the time
that the other allocator needed).
## On a 16-core AMD EPYC running Linux
Testing on a big Amazon EC2 instance ([r5a.4xlarge](https://aws.amazon.com/ec2/instance-types/))
consisting of a 16-core AMD EPYC 7000 at 2.5GHz
with 128GB ECC memory, running Ubuntu 18.04.1 with LibC 2.27 and GCC 7.3.0.
The first benchmark set consists of programs that allocate a lot. Relative
elapsed time:
![bench-r5a-4xlarge-t1](bench-r5a-4xlarge-t1.png)
and memory usage:
![bench-r5a-4xlarge-m1](bench-r5a-4xlarge-m1.png)
The benchmarks above are (with N=16 in our case):
- __cfrac__: by Dave Barrett, implementation of continued fraction factorization:
uses many small short-lived allocations. Factorizes as `./cfrac 175451865205073170563711388363274837927895`.
- __espresso__: a programmable logic array analyzer \[3].
- __barnes__: a hierarchical n-body particle solver \[4]. Simulates 163840 particles.
- __leanN__: by Leonardo de Moura _et al_, the [lean](https://github.com/leanprover/lean)
compiler, version 3.4.1, compiling its own standard library concurrently using N cores (`./lean --make -j N`).
Big real-world workload with intensive allocation, takes about 1:40s when running on a
single high-end core.
- __redis__: running the [redis](https://redis.io/) 5.0.3 server on
1 million requests pushing 10 new list elements and then requesting the
head 10 elements. Measures the requests handled per second.
- __alloc-test__: a modern [allocator test](http://ithare.com/testing-memory-allocators-ptmalloc2-tcmalloc-hoard-jemalloc-while-trying-to-simulate-real-world-loads/)
developed by by OLogN Technologies AG at [ITHare.com](http://ithare.com). Simulates intensive allocation workloads with a Pareto
size distribution. The `alloc-testN` benchmark runs on N cores doing 100&times;10<sup>6</sup>
allocations per thread with objects up to 1KB in size.
Using commit `94f6cb` ([master](https://github.com/node-dot-cpp/alloc-test), 2018-07-04)
We can see mimalloc outperforms the other allocators moderately but all
these modern allocators perform well.
In `cfrac`, mimalloc is about 13%
faster than jemalloc for many small and short-lived allocations.
The `cfrac` and `espresso` programs do not use much
memory (~1.5MB) so it does not matter too much, but still mimalloc uses about half the resident
memory of tcmalloc (and almost 5&times; less than Hoard on `espresso`).
_The `leanN` program is most interesting as a large realistic and concurrent
workload and there is a 6% speedup over both tcmalloc and jemalloc. This is
quite significant: if Lean spends (optimistically) 20% of its time in the allocator
that means that mimalloc is 1.5&times; faster than the others._
The `alloc-test` is very allocation intensive and we see the larger
diffrerences here. Since all allocators perform almost identical on `alloc-test1`
as `alloc-testN`, we can see that they are all excellent and scale (almost) linearly.
The second benchmark set test specific aspects of the allocators and
shows more extreme differences between allocators:
![bench-r5a-4xlarge-t2](bench-r5a-4xlarge-t2.png)
&nbsp;
![bench-r5a-4xlarge-m2](bench-r5a-4xlarge-m2.png)
The benchmarks in the second set are (again with N=16):
- __larson__: by Larson and Krishnan \[2]. Simulates a server workload using 100
separate threads where
they allocate and free many objects but leave some objects to
be freed by other threads. Larson and Krishnan observe this behavior
(which they call _bleeding_) in actual server applications, and the
benchmark simulates this.
- __sh6bench__: by [MicroQuill](http://www.microquill.com) as part of SmartHeap. Stress test for
single-threaded allocation where some of the objects are freed
in a usual last-allocated, first-freed (LIFO) order, but others
are freed in reverse order. Using the public [source](http://www.microquill.com/smartheap/shbench/bench.zip) (retrieved 2019-01-02)
- __sh8bench__: by [MicroQuill](http://www.microquill.com) as part of SmartHeap. Stress test for
multithreaded allocation (with N threads) where, just as in `larson`, some objects are freed
by other threads, and some objects freed in reverse (as in `sh6bench`).
Using the public [source](http://www.microquill.com/smartheap/SH8BENCH.zip) (retrieved 2019-01-02)
- __cache-scratch__: by Emery Berger _et al_ \[1]. Introduced with the Hoard
allocator to test for _passive-false_ sharing of cache lines: first some
small objects are allocated and given to each thread; the threads free that
object and allocate another one and access that repeatedly. If an allocator
allocates objects from different threads close to each other this will
lead to cache-line contention.
In the `larson` server workload mimalloc is 2.5&times; faster than
tcmalloc and jemalloc which is quite surprising -- probably due to the object
migration between different threads. Also in `sh6bench` mimalloc does much
better than the others (more than 4&times; faster than jemalloc). a
We cannot explain this well but believe it may be
caused in part by the "reverse" free-ing in `sh6bench`. Again in `sh8bench`
the mimalloc allocator handles object migration between threads much better .
The `cache-scratch` benchmark also demonstrates the different architectures
of the allocators nicely. With a single thread they all perform the same, but when
running with multiple threads the allocator induced false sharing of the
cache lines causes large run-time differences, where mimalloc is up to
20&times; faster than tcmalloc here. Only the original jemalloc does almost
as well (but the most recent version, jxmalloc, regresses). The
Hoard allocator is specifically designed to avoid this false sharing and we
are not sure why it is not doing well here (although it runs still 5&times; as
fast as tcmalloc and jxmalloc).
## On a 8-core Intel Xeon running Linux
Testing on a compute optimized Amazon EC2 instance ([c5d.2xlarge](https://aws.amazon.com/ec2/instance-types/))
consisting of a 8-core Intel Xeon Platinum at 3GHz (up to 3.5GHz turbo boost)
with 16GB ECC memory, running Ubuntu 18.04.1 with LibC 2.27 and GCC 7.3.0.
First the regular workload benchmarks (with N=8):
![bench-c5d-2xlarge-t1](bench-c5d-2xlarge-t1.png)
&nbsp;
![bench-c5d-2xlarge-m1](bench-c5d-2xlarge-m1.png)
Most results are quite similar to the 16-core AMD machine except the
the differences are less pronounced with all a bit closer to mimalloc performance.
This is shown too in the second set of benchmarks:
![bench-c5d-2xlarge-t2](bench-c5d-2xlarge-t2.png)
&nbsp;
![bench-c5d-2xlarge-m2](bench-c5d-2xlarge-m2.png)
On the server workload of `larson` everyone does a bit better on the 8-cores
than on 16. On the other benchmarks the performance does not improve though.
## On Windows (4-core Intel Xeon)
Testing on a HP Z4 G4 Workstation with a 4-core Intel® Xeon® W2123 at 3.6 GHz
with 16GB ECC memory, running Windows 10 Pro (version 10.0.17134 Build 17134)
with Visual Studio 2017 (version 15.8.9).
Since we cannot use `LD_PRELOAD` on Windows we compiled a subset of our
allocators and benchmarks and linked them statically. The **je** benchmark
is therefore equivalent to the **jx** benchmark in the previous graphs.
The **mc** allocator now refers to the standard Microsoft allocator.
Unfortunately we could not get Hoard to work on Windows at this time.
We used the Windows call `QueryPerformanceCounter` to measure elapsed wall-clock
times, and `GetProcessMemoryInfo` to measure the peak working set (rss).
First the regular workload benchmarks:
![bench-z4-win-t1](bench-z4-win-t1.png)
&nbsp;
![bench-z4-win-m1](bench-z4-win-m1.png)
Here mimalloc and tcmalloc perform very similar, and outperform the system
allocator by a significant margin. Somehow jemalloc does much worse than
running on Linux. It it not clear why yet, but it might be a compilation issue:
when running through the profiler the `__chkstk` routine takes
quite some time. This is a compiler inserted runtime function to check for enough
stack space if there are many local variables or when the compiler cannot make
a static estimate. Perhaps this is the culprit but it needs more investigation.
The second set of benchmarks shows again more pronounced differences:
![bench-z4-win-t2](bench-z4-win-t2.png)
&nbsp;
![bench-z4-win-m2](bench-z4-win-m2.png)
In the `larson` server workload mimalloc is 25% faster than
tcmalloc, and both significantly outperform the system allocator.
(again probably due to the object
migration between different threads).
Also in `sh6bench` and `sh8bench`, mimalloc scales much
better than the others.
## References
- \[1] Emery D. Berger, Kathryn S. McKinley, Robert D. Blumofe, and Paul R. Wilson.
_Hoard: A Scalable Memory Allocator for Multithreaded Applications_
the Ninth International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS-IX). Cambridge, MA, November 2000.
[pdf](http://www.cs.utexas.edu/users/mckinley/papers/asplos-2000.pdf)
- \[2] P. Larson and M. Krishnan. _Memory allocation for long-running server applications_. In ISMM, Vancouver, B.C., Canada, 1998.
[pdf](http://citeseemi.ist.psu.edu/viewdoc/download;jsessionid=5F0BFB4F57832AEB6C11BF8257271088?doi=10.1.1.45.1947&rep=rep1&type=pdf)
- \[3] D. Grunwald, B. Zorn, and R. Henderson.
_Improving the cache locality of memory allocation_. In R. Cartwright, editor,
Proceedings of the Conference on Programming Language Design and Implementation, pages 177–186, New York, NY, USA, June 1993.
[pdf](http://citeseemi.ist.psu.edu/viewdoc/download?doi=10.1.1.43.6621&rep=rep1&type=pdf)
- \[4] J. Barnes and P. Hut. _A hierarchical O(n*log(n)) force-calculation algorithm_. Nature, 324:446-449, 1986.
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