529ce23a76
The mm_struct contains a function pointer *get_unmapped_area(), which is set to either arch_get_unmapped_area() or arch_get_unmapped_area_topdown() during the initialization of the mm. Since the function pointer only ever points to two functions that are named the same across all arch's, a function pointer is not really required. In addition future changes will want to add versions of the functions that take additional arguments. So to save a pointers worth of bytes in mm_struct, and prevent adding additional function pointers to mm_struct in future changes, remove it and keep the information about which get_unmapped_area() to use in a flag. Add the new flag to MMF_INIT_MASK so it doesn't get clobbered on fork by mmf_init_flags(). Most MM flags get clobbered on fork. In the pre-existing behavior mm->get_unmapped_area() would get copied to the new mm in dup_mm(), so not clobbering the flag preserves the existing behavior around inheriting the topdown-ness. Introduce a helper, mm_get_unmapped_area(), to easily convert code that refers to the old function pointer to instead select and call either arch_get_unmapped_area() or arch_get_unmapped_area_topdown() based on the flag. Then drop the mm->get_unmapped_area() function pointer. Leave the get_unmapped_area() pointer in struct file_operations alone. The main purpose of this change is to reorganize in preparation for future changes, but it also converts the calls of mm->get_unmapped_area() from indirect branches into a direct ones. The stress-ng bigheap benchmark calls realloc a lot, which calls through get_unmapped_area() in the kernel. On x86, the change yielded a ~1% improvement there on a retpoline config. In testing a few x86 configs, removing the pointer unfortunately didn't result in any actual size reductions in the compiled layout of mm_struct. But depending on compiler or arch alignment requirements, the change could shrink the size of mm_struct. Link: https://lkml.kernel.org/r/20240326021656.202649-3-rick.p.edgecombe@intel.com Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Acked-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org> Cc: Borislav Petkov (AMD) <bp@alien8.de> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: Deepak Gupta <debug@rivosinc.com> Cc: Guo Ren <guoren@kernel.org> Cc: Helge Deller <deller@gmx.de> Cc: H. Peter Anvin (Intel) <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com> Cc: Kees Cook <keescook@chromium.org> Cc: Mark Brown <broonie@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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.. | ||
advise.c | ||
advise.h | ||
alloc_cache.h | ||
cancel.c | ||
cancel.h | ||
epoll.c | ||
epoll.h | ||
fdinfo.c | ||
fdinfo.h | ||
filetable.c | ||
filetable.h | ||
fs.c | ||
fs.h | ||
futex.c | ||
futex.h | ||
io_uring.c | ||
io_uring.h | ||
io-wq.c | ||
io-wq.h | ||
kbuf.c | ||
kbuf.h | ||
Makefile | ||
msg_ring.c | ||
msg_ring.h | ||
napi.c | ||
napi.h | ||
net.c | ||
net.h | ||
nop.c | ||
nop.h | ||
notif.c | ||
notif.h | ||
opdef.c | ||
opdef.h | ||
openclose.c | ||
openclose.h | ||
poll.c | ||
poll.h | ||
refs.h | ||
register.c | ||
register.h | ||
rsrc.c | ||
rsrc.h | ||
rw.c | ||
rw.h | ||
slist.h | ||
splice.c | ||
splice.h | ||
sqpoll.c | ||
sqpoll.h | ||
statx.c | ||
statx.h | ||
sync.c | ||
sync.h | ||
tctx.c | ||
tctx.h | ||
timeout.c | ||
timeout.h | ||
truncate.c | ||
truncate.h | ||
uring_cmd.c | ||
uring_cmd.h | ||
waitid.c | ||
waitid.h | ||
xattr.c | ||
xattr.h |