vpp: use vpp heap for libc

This makes libc use vpp main heap instead of the default libc heap.
This gives better visibility (accounting, tracing) on allocations
happening in external libraries called from vpp (eg. OpenSSL).

Type: feature

Change-Id: I5d8a673472145a4e090bedb443b8c58a967d1cca
Signed-off-by: Benoît Ganne <bganne@cisco.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/docs/troubleshooting/mem.rst b/docs/troubleshooting/mem.rst
new file mode 100644
index 00000000000..5475051c085
--- /dev/null
+++ b/docs/troubleshooting/mem.rst
@@ -0,0 +1,84 @@
+.. _memleak:
+
+*****************
+Memory leaks
+*****************
+
+Memory traces
+=============
+
+VPP supports memory traces to help debug (suspected) memory leaks. Each
+allocation/deallocation is instrumented so that the number of allocations and
+current global allocated size is maintained for each unique allocation stack
+trace.
+
+Looking at a memory trace can help diagnose where memory is (over-)used, and
+comparing memory traces at different point in time can help diagnose if and
+where memory leaks happen.
+
+To enable memory traces on main-heap:
+
+.. code-block:: console
+    $ vppctl memory-trace on main-heap
+
+To dump memory traces for analysis:
+
+.. code-block:: console
+    $ vppctl show memory-trace on main-heap
+    Thread 0 vpp_main
+      base 0x7fffb6422000, size 1g, locked, unmap-on-destroy, name 'main heap'
+	page stats: page-size 4K, total 262144, mapped 30343, not-mapped 231801
+	  numa 0: 30343 pages, 118.53m bytes
+	total: 1023.99M, used: 115.49M, free: 908.50M, trimmable: 908.48M
+	  free chunks 451 free fastbin blks 0
+	  max total allocated 1023.99M
+
+      Bytes    Count     Sample   Traceback
+     31457440        1 0x7fffbb31ad00 clib_mem_alloc_aligned_at_offset + 0x80
+				      clib_mem_alloc_aligned + 0x26
+				      alloc_aligned_8_8 + 0xe1
+				      clib_bihash_instantiate_8_8 + 0x76
+				      clib_bihash_init2_8_8 + 0x2ec
+				      clib_bihash_init_8_8 + 0x6a
+				      l2fib_table_init + 0x54
+				      set_int_l2_mode + 0x89
+				      int_l3 + 0xb4
+				      vlib_cli_dispatch_sub_commands + 0xeee
+				      vlib_cli_dispatch_sub_commands + 0xc62
+				      vlib_cli_dispatch_sub_commands + 0xc62
+       266768     5222 0x7fffbd79f978 clib_mem_alloc_aligned_at_offset + 0x80
+				      vec_resize_allocate_memory + 0xa8
+				      _vec_resize_inline + 0x240
+				      unix_cli_file_add + 0x83d
+				      unix_cli_listen_read_ready + 0x10b
+				      linux_epoll_input_inline + 0x943
+				      linux_epoll_input + 0x39
+				      dispatch_node + 0x336
+				      vlib_main_or_worker_loop + 0xbf1
+				      vlib_main_loop + 0x1a
+				      vlib_main + 0xae7
+				      thread0 + 0x3e
+    ....
+
+libc memory traces
+==================
+
+Internal VPP memory allocations rely on VPP main-heap, however when using
+external libraries, esp. in plugins (eg. OpenSSL library used by the IKEv2
+plugin), those external libraries usually manages memory using the standard
+libc malloc()/free()/... calls. This, in turn, makes use of the default
+libc heap.
+
+VPP has no knowledge of this heap and tools such as memory traces cannot be
+used.
+
+In order to enable the use of standard VPP debugging tools, this library
+replaces standard libc memory management calls with version using VPP
+main-heap.
+
+To use it, you need to use the `LD_PRELOAD` mechanism, eg.
+
+.. code-block:: console
+    ~# LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libvppmem_preload.so /usr/bin/vpp -c /etc/vpp/startup.conf
+
+You can then use tools such as memory traces as usual.