[docs][scudo] Add information about M_PURGE_ALL.

Add information about M_PURGE_ALL

Reviewed By: Chia-hungDuan

Differential Revision: https://reviews.llvm.org/D146336

diff --git a/llvm/docs/ScudoHardenedAllocator.rst b/llvm/docs/ScudoHardenedAllocator.rst
index 9c1cfa6..875d018 100644 (file)
--- a/llvm/docs/ScudoHardenedAllocator.rst
+++ b/llvm/docs/ScudoHardenedAllocator.rst
@@ -265,7 +265,16 @@ The following "mallopt" options are available (options are defined in
 |                           | the interval to the minimum and maximum value as      |
 |                           | specified at compile time).                           |
 +---------------------------+-------------------------------------------------------+
-| M_PURGE                   | Forces immediate memory reclaiming (value is unused). |
+| M_PURGE                   | Forces immediate memory reclaiming but does not       |
+|                           | reclaim everything. For smaller size classes, there   |
+|                           | is still some memory that is not reclaimed due to the |
+|                           | extra time it takes and the small amount of memory    |
+|                           | that can be reclaimed.                                |
+|                           | The value is ignored.                                 |
++---------------------------+-------------------------------------------------------+
+| M_PURGE_ALL               | Same as M_PURGE but will force release all possible   |
+|                           | memory regardless of how long it takes.               |
+|                           | The value is ignored.                                 |
 +---------------------------+-------------------------------------------------------+
 | M_MEMTAG_TUNING           | Tunes the allocator's choice of memory tags to make   |
 |                           | it more likely that a certain class of memory errors  |