Messages in this thread | | | Date | Mon, 10 Jan 2022 08:43:53 +0100 | From | Sebastian Andrzej Siewior <> | Subject | Re: [PATCH] locking/local_lock: Make the empty local_lock_*() function a macro. |
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On 2022-01-05 22:34:31 [-0500], Waiman Long wrote: > > I try out this patch and it indeed helps to reduce the object size of > functions that use local_lock(). However, the extra code isn't an additional > mov+add. > > Using folio_add_lru() as an example, > > Without the patch: > > 466 local_lock(&lru_pvecs.lock); > 0x00000000000032ee <+14>: mov $0x1,%edi > 0x00000000000032f3 <+19>: callq 0x32f8 <folio_add_lru+24> > 0x00000000000032f8 <+24>: callq 0x32fd <folio_add_lru+29>
The call here might be due to some debugging switches or compiler optimisation. I have with no debug and gcc-11: | # mm/swap.c:466: local_lock(&lru_pvecs.lock); | movq $lru_pvecs, %rbx #, tmp135 | movq %rbx, %rax # tmp135, tcp_ptr__ | #APP | # 466 "mm/swap.c" 1 | add %gs:this_cpu_off(%rip), %rax # this_cpu_off, tcp_ptr__
so it is mov per-CPU variable, add per-CPU offset.
Sebastian
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