doc: add valgrind suppression details

doc/contributing/investigating-native-memory-leaks.md

@@ -320,6 +320,109 @@ allocated. This is because by default the addon is compiled without
 the debug symbols which Valgrind needs to be able to provide more
 information.
 
+It is possible to hide leaks related to Node.js itself in future Valgrind runs
+using the suppression feature of Valgrind.
+
+## Generating a Valgrind suppression file
+
+Valgrind uses suppression files to hide issues found from the summary. Generate
+a log file with embedded suppressions using the `--gen-suppressions` and
+`--log-file` flags:
+
+```bash
+valgrind --leak-check=full \
+   --gen-suppressions=all \
+   --log-file=./valgrind-out.txt \
+   node hello.js
+```
+
+Valgrind will save the output to the log file specified. After each heap in the
+summary, Valgrind will include a suppression record: a structure that Valgrind
+can use to ignore specific memory issues. Suppression records can be saved to a
+suppression file which Valgrind can use in subsequent executions to hide various
+memory errors. This is an example of the suppression records from the previous
+call:
+
+```text
+{
+   <insert_a_suppression_name_here>
+   Memcheck:Value8
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   obj:/home/kevin/.nvm/versions/node/v12.14.1/bin/node
+   fun:_ZN2v88internal12_GLOBAL__N_16InvokeEPNS0_7IsolateERKNS1_12InvokeParamsE
+   fun:_ZN2v88internal9Execution4CallEPNS0_7IsolateENS0_6HandleINS0_6ObjectEEES6_iPS6_
+   fun:_ZN2v88Function4CallENS_5LocalINS_7ContextEEENS1_INS_5ValueEEEiPS5_
+}
+{
+   <insert_a_suppression_name_here>
+   Memcheck:Leak
+   match-leak-kinds: definite
+   fun:_Znwm
+   fun:napi_module_register
+   fun:call_init.part.0
+   fun:call_init
+   fun:_dl_init
+   fun:_dl_catch_exception
+   fun:dl_open_worker
+   fun:_dl_catch_exception
+   fun:_dl_open
+   fun:dlopen_doit
+   fun:_dl_catch_exception
+   fun:_dl_catch_error
+   fun:_dlerror_run
+}
+{
+   <insert_a_suppression_name_here>
+   Memcheck:Leak
+   match-leak-kinds: possible
+   fun:calloc
+   fun:allocate_dtv
+   fun:_dl_allocate_tls
+   fun:allocate_stack
+   fun:pthread_create@@GLIBC_2.2.5
+   fun:_ZN4node9inspector5Agent5StartERKSsRKNS_12DebugOptionsESt10shared_ptrINS_8HostPortEEb
+   fun:_ZN4node11Environment19InitializeInspectorESt10unique_ptrINS_9inspector21ParentInspectorHandleESt14default_deleteIS3_EE
+   fun:_ZN4node16NodeMainInstance21CreateMainEnvironmentEPi
+   fun:_ZN4node16NodeMainInstance3RunEv
+   fun:_ZN4node5StartEiPPc
+   fun:(below main)
+}
+```
+
+Create a file (eg. `node-12.14.1.supp`) with the contents of the suppression
+records, and run Valgrind with the suppression file previously created:
+
+```bash
+valgrind --leak-check=full \
+   --suppressions=./node-12.14.1.supp \
+   node hello.js
+```
+
+Now, the Valgrind leak summary for suppressed issues are only mentioned as
+`suppressed` in the leak summary:
+
+```console
+==12471== HEAP SUMMARY:
+==12471==     in use at exit: 8,067 bytes in 31 blocks
+==12471==   total heap usage: 16,482 allocs, 16,451 frees, 17,255,689 bytes allocated
+==12471==
+==12471== LEAK SUMMARY:
+==12471==    definitely lost: 0 bytes in 0 blocks
+==12471==    indirectly lost: 0 bytes in 0 blocks
+==12471==      possibly lost: 0 bytes in 0 blocks
+==12471==    still reachable: 7,699 bytes in 29 blocks
+==12471==                       of which reachable via heuristic:
+==12471==                         multipleinheritance: 48 bytes in 1 blocks
+==12471==         suppressed: 368 bytes in 2 blocks
+```
+
 ## Enabling debug symbols to get more information
 
 Leaks may be either in addons or Node.js itself. The sections which