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charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Oct 7, 2024 at 4:50=E2=80=AFPM Al Viro wr= ote: > > On Mon, Oct 07, 2024 at 10:52:37AM +0200, Uros Bizjak wrote: > > Use atomic64_inc_return(&ref) instead of atomic64_add_return(1, &ref) > > to use optimized implementation and ease register pressure around > > the primitive for targets that implement optimized variant. > > > > Signed-off-by: Uros Bizjak > > Cc: Alexander Viro > > Cc: Christian Brauner > > Cc: Jan Kara > > --- > > fs/namespace.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/fs/namespace.c b/fs/namespace.c > > index 93c377816d75..9a3c251d033d 100644 > > --- a/fs/namespace.c > > +++ b/fs/namespace.c > > @@ -3901,7 +3901,7 @@ static struct mnt_namespace *alloc_mnt_ns(struct = user_namespace *user_ns, bool a > > } > > new_ns->ns.ops =3D &mntns_operations; > > if (!anon) > > - new_ns->seq =3D atomic64_add_return(1, &mnt_ns_seq); > > + new_ns->seq =3D atomic64_inc_return(&mnt_ns_seq); > > On which load do you see that path hot enough for the change to > make any difference??? It is not performance, but code size improvement, as stated in the commit message. The difference on x86_32 (that implements atomic64_inc_return()) is: eeb: b8 01 00 00 00 mov $0x1,%eax ef0: 31 d2 xor %edx,%edx ef2: b9 20 00 00 00 mov $0x20,%ecx ef3: R_386_32 .data ef7: e8 fc ff ff ff call ef8 ef8: R_386_PC32 atomic64_add_return_cx8 efc: 89 46 20 mov %eax,0x20(%esi) eff: 89 56 24 mov %edx,0x24(%esi) vs: eeb: be 20 00 00 00 mov $0x20,%esi eec: R_386_32 .data ef0: e8 fc ff ff ff call ef1 ef1: R_386_PC32 atomic64_inc_return_cx8 ef5: 89 43 20 mov %eax,0x20(%ebx) ef8: 89 53 24 mov %edx,0x24(%ebx) Uros.