Some pages (e.g., hugetlb pages) cannot be purged, and should be
prioritized for reuse. A custom extent_alloc hook signals this by
OR'ing EXTENT_ALLOC_FLAG_PINNED into the low bits of the returned
pointer; jemalloc strips the flag bits and caches pinned extents in
a dedicated ecache_pinned, separate from the dirty/muzzy decay
pipeline.
Pinned extents do not coalesce eagerly, except for ones larger than
SC_LARGE_MINCLASS. A prefer-small policy reuses the smallest fitting
pinned extent, to avoid unnecessary split/fragmentation.
Three changes to make pa_microbench easier to drive for fragmentation
experiments:
- Replace HPA_SHARD_OPTS_DEFAULT use with a single editable g_hpa_opts
global. The microbench does not consult MALLOC_CONF for HPA shard opts,
so this is the place to set the baseline configuration (slab_max_alloc,
hugification_threshold, dirty_mult, hugify_delay_ms, purge_threshold,
hugify_style, etc.).
- Add -n/--nshards N to override the shard count derived from the trace.
When set, each event is routed to (event->shard_ind % N), letting us
study the impact of arena consolidation. Without the flag the behavior
is unchanged (num_shards = max_shard_id + 1).
- Bump MAX_ALLOCATIONS from 10M to 200M so the full ~50M-event adfinder
trace (and similar) fits in the in-memory event buffer.
* Replace std::__throw_bad_alloc call with standard C++
Since December of 2025, std::__throw_bad_alloc is no longer visible
through #include <new> causing jemalloc build failures with gcc 16.
As far as I can tell, all std::__throw_bad_alloc did was arrange to
raise a std::bad_alloc exception if exceptions are enabled. I am not
sure whether its usage was truly meaningful in jemalloc since the call
is wrapped in a try catch and any usage of try catch is considered an
error when compiling with -fno-exceptions on gcc, at least.
This change adds a check to configure.ac that determines whether
exceptions are enabled by compiling a simple try catch that raises a
std::bad_alloc exception. If that test succeeds, the macro
JEMALLOC_HAVE_CXX_EXCEPTIONS is defined, and jemalloc will raise an
exception. Otherwise, we call std::terminate() to abort.
This was tested on FreeBSD with the gcc16 port with and without exceptions
enabled.
* Replace std::set_new_handler calls with std::get_new_handler
Previously, std::set_new_handler was used as a workaround for
compilers with only partial support for C++11. Now that C++14 is a
requirement to enable C++ support, we can assume std::get_new_handler
is available.
pa_microbench was creating its own emap_t per shard on top of the
arena_emap_global that JET malloc initializes during jet_malloc(16)
at startup, breaking the production assumption of one rtree per
process. Fix it by reusing the existing JET emap.
* Document new mallctl interfaces added since 5.3.0
Add documentation for the following new mallctl entries:
- opt.debug_double_free_max_scan: double-free detection scan limit
- opt.prof_bt_max: max profiling backtrace depth
- opt.disable_large_size_classes: page-aligned large allocations
- opt.process_madvise_max_batch: batched process_madvise purging
- thread.tcache.max: per-thread tcache_max control
- thread.tcache.ncached_max.read_sizeclass: query ncached_max
- thread.tcache.ncached_max.write: set ncached_max per size range
- arena.<i>.name: get/set arena names
- arenas.hugepage: hugepage size
- approximate_stats.active: lightweight active bytes estimate
Remove config.prof_frameptr since it still needs more development
and is still experimental.
Co-authored-by: lexprfuncall <carl.shapiro@gmail.com>
When san_bump_grow_locked fails, it sets sba->curr_reg to NULL.
The old curr_reg (saved in to_destroy) was never freed or restored,
leaking the virtual memory extent. Restore sba->curr_reg from
to_destroy on failure so the old region remains usable.
An extra 'size' argument was passed where 'slab' (false) should be,
shifting all subsequent arguments: slab got size (nonzero=true),
szind got false (0), and sn got SC_NSIZES instead of a proper serial
number from extent_sn_next(). Match the correct pattern used by the
gap edata_init call above.
The sentinel fill loop used sz_pind2sz_tab[pind] (constant) instead
of sz_pind2sz_tab[i] (loop variable), writing only to the first
entry repeatedly and leaving subsequent entries uninitialized.
When emap_try_acquire_edata_neighbor returned a non-NULL neighbor but
the size check failed, the neighbor was never released from
extent_state_merging, making it permanently invisible to future
allocation and coalescing operations.
Release the neighbor when it doesn't meet the size requirement,
matching the pattern used in extent_recycle_extract.
Used size_t (unsigned) instead of ssize_t for the return value of
malloc_read_fd, which returns -1 on error. With size_t, -1 becomes
a huge positive value, bypassing the error check and corrupting the
remaining byte count.
Returned LG_PAGE (log2 of page size, e.g. 12) instead of PAGE (actual
page size, e.g. 4096) when sysconf(_SC_PAGESIZE) failed. This would
cause os_page to be set to an absurdly small value, breaking all
page-aligned operations.
newly_mapped_size was set unconditionally in the ecache_alloc_grow
fallback path, even when the allocation returned NULL. This inflated
pac_mapped stats without a corresponding deallocation to correct them.
Guard the assignment with an edata != NULL check, matching the pattern
used in the batched allocation path above it.
When called with size==0, the else branch wrote to str[size-1] which
is str[(size_t)-1], a massive out-of-bounds write. Standard vsnprintf
allows size==0 to mean "compute length only, write nothing".
Add unit test for the size==0 case.
Same pattern as arenas_bin_i_index: used > instead of >= allowing
access one past the end of bstats[] and lstats[] arrays.
Add unit tests that verify boundary indices return ENOENT.
