- NetBSD overcommits
- When mapping pages, use the maximum of the alignment requested and the
compiled-in PAGE constant which might be greater than the current kernel
pagesize, since we compile binaries with the maximum page size supported
by the architecture (so that they work with all kernels).
some architecture like AArch64 may not have the open syscall, but have
openat syscall. so check and use SYS_openat if SYS_openat available if
SYS_open is not supported at init_thp_state.
in case `malloc_read_fd` returns a negative error number, the result
would afterwards be casted to an unsigned size_t, and may have
theoretically caused an out-of-bounds memory access in the following
`strncmp` call.
This makes it directly use MAP_EXCL and MAP_ALIGNED() instead
of weird workarounds involving mapping at random places and then
unmapping parts of them.
When configured with --with-lg-page, it's possible for the configured page size
to be greater than the system page size, in which case the page address may only
be aligned with the system page size.
"always" marks all user mappings as MADV_HUGEPAGE; while "never" marks all
mappings as MADV_NOHUGEPAGE. The default setting "default" does not change any
settings. Note that all the madvise calls are part of the default extent hooks
by design, so that customized extent hooks have complete control over the
mappings including hugepage settings.
This attempts to use VM_OVERCOMMIT OID - newly introduced in -CURRENT
few days ago, specifically for this purpose - instead of querying the
sysctl by its string name. Due to how syctlbyname(3) works, this means
we do one syscall during binary startup instead of two.
Signed-off-by: Edward Tomasz Napierala <trasz@FreeBSD.org>
This avoids sysctl(2) syscall during binary startup, using the value
passed in the ELF aux vector instead.
Signed-off-by: Edward Tomasz Napierala <trasz@FreeBSD.org>
On x86 Linux, we define our own MADV_FREE if madvise(2) is available, but no
MADV_FREE is detected. This allows the feature to be built in and enabled with
runtime detection.
It's possible to build with lazy purge enabled but depoly to systems without
such support. In this case, rely on the boot time detection instead of keep
making unnecessary madvise calls (which all returns EINVAL).
To avoid the high RSS caused by THP + low usage arena (i.e. THP becomes a
significant percentage), added a new "auto" option which will only start using
THP after a base allocator used up the first THP region. Starting from the
second hugepage (in a single arena), "auto" behaves the same as "always",
i.e. madvise hugepage right away.
As part of the metadata_thp support, We now have a separate swtich
(JEMALLOC_HAVE_MADVISE_HUGE) for MADV_HUGEPAGE availability. Use that instead
of JEMALLOC_THP (which doesn't guard pages_huge anymore) in tests.
Older Linux systems don't have O_CLOEXEC. If that's the case, we fcntl
immediately after open, to minimize the length of the racy period in
which an
operation in another thread can leak a file descriptor to a child.
Some architectures like AArch64 may not have the open syscall because it
was superseded by the openat syscall, so check and use SYS_openat if
SYS_open is not available.
Additionally, Android headers for AArch64 define SYS_open to __NR_open,
even though __NR_open is undefined. Undefine SYS_open in that case so
SYS_openat is used.
All mappings continue to be PAGE-aligned, even if the system page size
is smaller. This change is primarily intended to provide a mechanism
for supporting multiple page sizes with the same binary; smaller page
sizes work better in conjunction with jemalloc's design.
This resolves#467.
This is a biggy. jemalloc_internal.h has been doing multiple jobs for a while
now:
- The source of system-wide definitions.
- The catch-all include file.
- The module header file for jemalloc.c
This commit splits up this functionality. The system-wide definitions
responsibility has moved to jemalloc_preamble.h. The catch-all include file is
now jemalloc_internal_includes.h. The module headers for jemalloc.c are now in
jemalloc_internal_[externs|inlines|types].h, just as they are for the other
modules.
Split purging into lazy and forced variants. Use the forced variant for
zeroing dss.
Add support for NULL function pointers as an opt-out mechanism for the
dalloc, commit, decommit, purge_lazy, purge_forced, split, and merge
fields of extent_hooks_t.
Add short-circuiting checks in large_ralloc_no_move_{shrink,expand}() so
that no attempt is made if splitting/merging is not supported.
This resolves#268.
Add the --with-lg-hugepage configure option, but automatically configure
LG_HUGEPAGE even if it isn't specified.
Add the pages_[no]huge() functions, which toggle huge page state via
madvise(..., MADV_[NO]HUGEPAGE) calls.
Add feature tests for the MADV_FREE and MADV_DONTNEED flags to
madvise(2), so that MADV_FREE is detected and used for Linux kernel
versions 4.5 and newer. Refactor pages_purge() so that on systems which
support both flags, MADV_FREE is preferred over MADV_DONTNEED.
This resolves#387.
Some applications wrap various system calls, and if they call the
allocator in their wrappers, unexpected reentry can result. This is not
a general solution (many other syscalls are spread throughout the code),
but this resolves a bootstrapping issue that is apparently common.
This resolves#443.
If the OS overcommits:
- Commit all mappings in pages_map() regardless of whether the caller
requested committed memory.
- Linux-specific: Specify MAP_NORESERVE to avoid
unfortunate interactions with heuristic overcommit mode during
fork(2).
This resolves#193.
Only set the unzeroed flag when initializing the entire mapbits entry,
rather than mutating just the unzeroed bit. This simplifies the
possible mapbits state transitions.
Add the "arena.<i>.chunk_hooks" mallctl, which replaces and expands on
the "arena.<i>.chunk.{alloc,dalloc,purge}" mallctls. The chunk hooks
allow control over chunk allocation/deallocation, decommit/commit,
purging, and splitting/merging, such that the application can rely on
jemalloc's internal chunk caching and retaining functionality, yet
implement a variety of chunk management mechanisms and policies.
Merge the chunks_[sz]ad_{mmap,dss} red-black trees into
chunks_[sz]ad_retained. This slightly reduces how hard jemalloc tries
to honor the dss precedence setting; prior to this change the precedence
setting was also consulted when recycling chunks.
Fix chunk purging. Don't purge chunks in arena_purge_stashed(); instead
deallocate them in arena_unstash_purged(), so that the dirty memory
linkage remains valid until after the last time it is used.
This resolves#176 and #201.
