This change adds support for writing pid namespaces to the filename of a
heap profile. When running with namespaces pids may reused across
namespaces and if mounts are shared where profiles are written there is
not a great way to differentiate profiles between pids.
Signed-off-by: Daniel Hodges <hodges.daniel.scott@gmail.com>
Signed-off-by: Daniel Hodges <hodgesd@fb.com>
For better or worse, Jemalloc has a significant number of global
variables. Making all eligible global variables `static` and/or `const`
at least makes it slightly easier to reason about them, as these
qualifications communicate to the programmer restrictions on their use
without having to `grep` the whole codebase.
The previous approach managed the thread name in a separate buffer, which causes
races because the thread name update (triggered by new samples) can happen at
the same time as prof dumping (which reads the thread names) -- these two
operations are under separate locks to avoid blocking each other. Implemented
the thread name storage as part of the tdata struct, which resolves the lifetime
issue and also avoids internal alloc / dalloc during prof_sample.
The added hooks hooks.prof_sample and hooks.prof_sample_free are intended to
allow advanced users to track additional information, to enable new ways of
profiling on top of the jemalloc heap profile and sample features.
The sample hook is invoked after the allocation and backtracing, and forwards
the both the allocation and backtrace to the user hook; the sample_free hook
happens before the actual deallocation, and forwards only the ptr and usz to the
hook.
The option makes the process to exit with error code 1 if a memory leak
is detected. This is useful for implementing automated tools that rely
on leak detection.
Existing backtrace implementations skip native stack frames from runtimes like
Python. The hook allows to augment the backtraces to attribute allocations to
native functions in heap profiles.
The prof initialization is done only when opt_prof is true. This change makes
sure the prof_* mallctls only have limited read access (i.e. no access to prof
internals) when opt_prof is false.
In addition, initialize the global prof mutexes even if opt_prof is false. This
makes sure the mutex stats are set properly.
This gives more accurate attribution of bytes and counts to stack traces,
without introducing backwards incompatibilities in heap-profile parsing tools.
We track the ideal reported (to the end user) number of bytes more carefully
inside core jemalloc. When dumping heap profiles, insteading of outputting our
counts directly, we output counts that will cause parsing tools to give a result
close to the value we want.
We retain the old version as an opt setting, to let users who are tracking
values on a per-component basis to keep their metrics stable until they decide
to switch.
