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[PATCH 1/2] Add note on MALLOC_MMAP_* environment variables
- From: Siddhesh Poyarekar <siddhesh at sourceware dot org>
- To: libc-alpha at sourceware dot org
- Date: Mon, 10 Oct 2016 22:56:27 +0530
- Subject: [PATCH 1/2] Add note on MALLOC_MMAP_* environment variables
- Authentication-results: sourceware.org; auth=none
The mallopt parameters manual does not mention the environment
variables that can be used to set these parameters at program startup.
Mention those environment variables for completeness.
* manual/memory.texi: Add environment variable alternatives to
setting mallopt parameters.
---
manual/memory.texi | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/manual/memory.texi b/manual/memory.texi
index 5383105..222f126 100644
--- a/manual/memory.texi
+++ b/manual/memory.texi
@@ -1113,12 +1113,18 @@ choices for @var{param}, as defined in @file{malloc.h}, are:
@item M_MMAP_MAX
The maximum number of chunks to allocate with @code{mmap}. Setting this
to zero disables all use of @code{mmap}.
+
+This parameter can also be set for the process at startup by setting the
+environment variable @code{MALLOC_MMAP_MAX_} to the desired value.
@item M_MMAP_THRESHOLD
All chunks larger than this value are allocated outside the normal
heap, using the @code{mmap} system call. This way it is guaranteed
that the memory for these chunks can be returned to the system on
@code{free}. Note that requests smaller than this threshold might still
be allocated via @code{mmap}.
+
+This parameter can also be set for the process at startup by setting the
+environment variable @code{MALLOC_MMAP_THRESHOLD_} to the desired value.
@comment TODO: @item M_MXFAST
@item M_PERTURB
If non-zero, memory blocks are filled with values depending on some
@@ -1128,16 +1134,25 @@ use of uninitialized or freed heap memory. Note that this option does not
guarantee that the freed block will have any specific values. It only
guarantees that the content the block had before it was freed will be
overwritten.
+
+This parameter can also be set for the process at startup by setting the
+environment variable @code{MALLOC_MMAP_PERTURB_} to the desired value.
@item M_TOP_PAD
This parameter determines the amount of extra memory to obtain from the
system when a call to @code{sbrk} is required. It also specifies the
number of bytes to retain when shrinking the heap by calling @code{sbrk}
with a negative argument. This provides the necessary hysteresis in
heap size such that excessive amounts of system calls can be avoided.
+
+This parameter can also be set for the process at startup by setting the
+environment variable @code{MALLOC_TOP_PAD_} to the desired value.
@item M_TRIM_THRESHOLD
This is the minimum size (in bytes) of the top-most, releasable chunk
that will cause @code{sbrk} to be called with a negative argument in
order to return memory to the system.
+
+This parameter can also be set for the process at startup by setting the
+environment variable @code{MALLOC_TRIM_THRESHOLD_} to the desired value.
@end table
@end deftypefun
--
2.7.4