update readme

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@@ -0,0 +1,42 @@
+# Windows Override
+
+Dynamically overriding mimalloc on Windows is robust and has the
+particular advantage to be able to redirect all malloc/free calls that go through
+the (dynamic) C runtime allocator, including those from other DLL's or libraries.
+As it intercepts all allocation calls on a low level, it can be used reliably 
+on large programs that include other 3rd party components.
+There are four requirements to make the overriding work robustly:
+
+1. Use the C-runtime library as a DLL (using the `/MD` or `/MDd` switch).
+
+2. Link your program explicitly with `mimalloc-override.dll` library.
+   To ensure the `mimalloc-override.dll` is loaded at run-time it is easiest to insert some
+    call to the mimalloc API in the `main` function, like `mi_version()`
+    (or use the `/INCLUDE:mi_version` switch on the linker). See the `mimalloc-override-test` project
+    for an example on how to use this. 
+
+3. The `mimalloc-redirect.dll` (or `mimalloc-redirect32.dll`) must be put
+   in the same folder as the main `mimalloc-override.dll` at runtime (as it is a dependency of that DLL).
+   The redirection DLL ensures that all calls to the C runtime malloc API get redirected to
+   mimalloc functions (which reside in `mimalloc-override.dll`).
+
+4. Ensure the `mimalloc-override.dll` comes as early as possible in the import
+   list of the final executable (so it can intercept all potential allocations).
+
+For best performance on Windows with C++, it
+is also recommended to also override the `new`/`delete` operations (by including
+[`mimalloc-new-delete.h`](https://github.com/microsoft/mimalloc/blob/master/include/mimalloc-new-delete.h) a single(!) source file in your project).
+
+The environment variable `MIMALLOC_DISABLE_REDIRECT=1` can be used to disable dynamic
+overriding at run-time. Use `MIMALLOC_VERBOSE=1` to check if mimalloc was successfully redirected.
+
+# Minject
+
+We cannot always re-link an executable with `mimalloc-override.dll`, and similarly, we cannot always
+ensure the the DLL comes first in the import table of the final executable.
+We can in many cases though patch existing executables without any recompilation
+if they are linked with the dynamic C runtime (`ucrtbase.dll`) -- just put the `mimalloc-override.dll`
+into the import table (and put `mimalloc-redirect.dll` in the same folder)
+Such patching can be done for example with [CFF Explorer](https://ntcore.com/?page_id=388)).
+
+The `minject` program can also do this from the command line, use `minject --help` for options.

readme.md

@@ -29,6 +29,8 @@ It also includes a robust way to override the default allocator in [Windows](#ov
   bounded worst-case times with reference counting).
   Partly due to its simplicity, mimalloc has been ported to many systems (Windows, macOS,
   Linux, WASM, various BSD's, Haiku, MUSL, etc) and has excellent support for dynamic overriding.
+  At the same time, it is an industrial strength allocator that runs (very) large scale
+  distributed services on thousands of machines with excellent worst case latencies.
 - __free list sharding__: instead of one big free list (per size class) we have
   many smaller lists per "mimalloc page" which reduces fragmentation and
   increases locality --
@@ -439,7 +441,7 @@ This is provided by [`mimalloc-override.h`](https://github.com/microsoft/mimallo
 under your control or otherwise mixing of pointers from different heaps may occur!
 
 
-## Tools
+# Tools
 
 Generally, we recommend using the standard allocator with memory tracking tools, but mimalloc
 can also be build to support the [address sanitizer][asan] or the excellent [Valgrind] tool. 
@@ -447,7 +449,7 @@ Moreover, it can be build to support Windows event tracing ([ETW]).
 This has a small performance overhead but does allow detecting memory leaks and byte-precise 
 buffer overflows directly on final executables. See also the `test/test-wrong.c` file to test with various tools.
 
-### Valgrind
+## Valgrind
 
 To build with [valgrind] support, use the `MI_TRACK_VALGRIND=ON` cmake option:
 
@@ -481,7 +483,7 @@ Valgrind support is in its initial development -- please report any issues.
 [Valgrind]: https://valgrind.org/
 [valgrind-soname]: https://valgrind.org/docs/manual/manual-core.html#opt.soname-synonyms
 
-### ASAN
+## ASAN
 
 To build with the address sanitizer, use the `-DMI_TRACK_ASAN=ON` cmake option:
 
@@ -510,7 +512,7 @@ Adress sanitizer support is in its initial development -- please report any issu
 
 [asan]: https://github.com/google/sanitizers/wiki/AddressSanitizer
 
-### ETW
+## ETW
 
 Event tracing for Windows ([ETW]) provides a high performance way to capture all allocations though
 mimalloc and analyze them later. To build with ETW support, use the `-DMI_TRACK_ETW=ON` cmake option.