Empty memory profiler:
The empty memory profiler identifies large allocations of potentially unused
memory. To do so, it scans allocated memory for runs of 4096 bytes or more
containing a pattern that indicates unused memory. The memory scan takes place
on free() and during a live heap walk. The results are stored in the MEM_LIVE
counter for both freed and leaked memory. The recorded stack frames always
belong to the resource allocation.
In its standard mode (-ep), the empty memory profiler looks for memory pages
filled with zero bytes. Such pages can occur due to deliberately setting memory
to zero, for instance by calloc(), memset(), or initializers. Zero-filled
pages can also be the result of memory allocated by mmap of /dev/zero but
unused until the profiler scans the memory.
If started as -ei, the profiler initializes allocated memory with a magic
pattern” (0xAA). As a result, only memory that is deliberately set to zero is
reported.
If started as -eu, the profiler initializes allocated memory as with the -ei
option. However, it records only pages filled with the magic byte. Thereyby, it
identifies allocated memory that has never been touched (but that also might
have never been mapped to physical memory).
Regular expression collapsing.
If pcre is available at build time, you can now pass a
set of perl like regular expressions as an argument of igprof-analyze to
collapse nodes in the report. This is done via the following syntax:
igprof-analyze -mr "s/<regex-to-match>/<substitution>/;s/<regex-to-match-2>/<substitution-2>/" <rest of the arguments>
for exaple you can do:
igprof-analyze -mr "s/Py_.*/PYTHON/" ...
to change all the symbols coming from the Python API to be referred as “PYTHON”.
Differentiate calls based on anchestors (new in 5.9.11)
The -ma / --merge-ancestors option has syntax:
-ma "REGEX1[>REGEX2[>...[>REGEX<N>]]]/NEW_NAME"
with this option igprof-analyse goes trough nodes in the call tree and checks
if node is child of ancestors that matches to REGEX<N> list. Node that
matches REGEX<N> and is child of all ancestors that matches previos regular
expressions will renamed as NEW_NAME. Also all child of the node REGEX<N> will
get the name NEW_NAME:orginal_name.
Ancestors got to match in order. REGEX1 is the oldest and REGEX2 is the 2nd
oldest.
For example program has function foo which calls bar and bar calls foobar and
at some other place the program calls only bar which then calls foobar.
-ma "foo>bar>foobar/foobar: child of foo and bar" would rename foobar at
the first case but leave foobar unchanged at the second case.
Node doesn’t need to be direct child of ancestor. For example -ma
"foo>foobar/foobar: has foo ancestor" would rename foobar if foo is ancestor of
the foobar.
Experimental energy profiling.
Experimental energy profiling is available if you build igprof on a machine
which has PAPI available. You can enable it by passing -ng as an option at
profile time.