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.
Previously if a thread does only allocations, it stays on the slow path /
minimal initialized state forever. However, dealloc-only is a valid pattern for
dedicated reclamation threads -- this means thread cache is disabled (no batched
flush) for them, which causes high overhead and contention.
Added the condition to fully initialize TSD when a fair amount of dealloc
activities are observed.
Add new runtime option `debug_double_free_max_scan` that specifies the max
number of stack entries to scan in the cache bit when trying to detect the
double free bug (currently debug build only).
Due to a bug in sec initialization, the number of cached size classes
was equal to 198. The bug caused the creation of more than a hundred of
unused bins, although it didn't affect the caching logic.
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.
Under high concurrency / heavy test load (e.g. using run_tests.sh), the
background thread may not get scheduled for a longer period of time. Retry 100
times max before bailing out.
On deallocation, sampled pointers (specially aligned) get junked and stashed
into tcache (to prevent immediate reuse). The expected behavior is to have
read-after-free corrupted and stopped by the junk-filling, while
write-after-free is checked when flushing the stashed pointers.
Many profiling related tests make assumptions on the profiling settings,
e.g. opt_prof is off by default, and prof_active is default on when opt_prof is
on. However the default settings can be changed via --with-malloc-conf at build
time. Fixing the tests by adding the assumed settings explicitly.
nstime module guarantees monotonic clock update within a single nstime_t. This
means, if two separate nstime_t variables are read and updated separately,
nstime_subtract between them may result in underflow. Fixed by switching to the
time since utility provided by nstime.
Currently used only for guarding purposes, the hint is used to determine
if the allocation is supposed to be frequently reused. For example, it
might urge the allocator to ensure the allocation is cached.
While initially this file contained helper functions for one particular
test, now its usage spread across different test files. Purpose has
shifted towards a collection of handy arena ctl wrappers.
With prof enabled, number of page aligned allocations doesn't match the
number of slab "ends" because prof allocations skew the addresses. It
leads to 'pages' array overflow and hard to debug failures.
In order for nstime_update to handle non-monotonic clocks, it requires the input
nstime to be initialized -- when reading for the first time, zero init has to be
done. Otherwise random stack value may be seen as clocks and returned.
As the code evolves, some code paths that have previously assigned
deferred_work_generated may cease being reached. This would leave the value
uninitialized. This change initializes the value for safety.
Adding guarded extents, which are regular extents surrounded by guard pages
(mprotected). To reduce syscalls, small guarded extents are cached as a
separate eset in ecache, and decay through the dirty / muzzy / retained pipeline
as usual.
This mallctl accepts an arena_config_t structure which
can be used to customize the behavior of the arena.
Right now it contains extent_hooks and a new option,
metadata_use_hooks, which controls whether the extent
hooks are also used for metadata allocation.
The medata_use_hooks option has two main use cases:
1. In heterogeneous memory systems, to avoid metadata
being placed on potentially slower memory.
2. Avoiding virtual memory from being leaked as a result
of metadata allocation failure originating in an extent hook.
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 change allows every allocator conforming to PAI communicate that it
deferred some work for the future. Without it if a background thread goes into
indefinite sleep, there is no way to notify it about upcoming deferred work.
