On 2023/8/8 11:26, Matthew Wilcox wrote: > On Tue, Aug 08, 2023 at 04:16:57AM +0100, Matthew Wilcox wrote: >> On Tue, Aug 08, 2023 at 11:08:36AM +0800, Miaohe Lin wrote: >>> On 2023/8/8 10:31, Matthew Wilcox wrote: >>>> On Tue, Aug 08, 2023 at 09:58:31AM +0800, Miaohe Lin wrote: >>>>> kswapd_stop() and kcompactd_stop() are only called when MEMORY_HOTREMOVE >>>>> is enabled. So wrap them under CONFIG_MEMORY_HOTREMOVE and further remove >>>>> __meminit annotation. No functional change intended. >>>> >>>> I don't understand why this is an improvement. If CONFIG_MEMORY_HOTREMOVE >>>> is disabled, the linker drops this section (... right?) If it's enabled, >>> >>> When CONFIG_MEMORY_HOTREMOVE is disabled, without this patch: >>> >>> size mm/compaction.o >>> text data bss dec hex filename >>> 103164 30873 0 134037 20b95 mm/compaction.o >>> >>> size mm/vmscan.o >>> text data bss dec hex filename >>> 158775 49612 64 208451 32e43 mm/vmscan.o >>> >>> while with this patch: >>> >>> size mm/compaction.o >>> text data bss dec hex filename >>> 102915 30865 0 133780 20a94 mm/compaction.o >>> >>> size mm/vmscan.o >>> text data bss dec hex filename >>> 158534 49604 64 208202 32d4a mm/vmscan.o >>> >>> We can reduce each .o by ~250 bytes. >> >> But this is before the linker step! That will be where the meminit >> sections get dropped. Assuming they are; I haven't verified. You need >> to compare before/after of the vmlinux, not the individual .o files. When CONFIG_MEMORY_HOTREMOVE is disabled, without patch: size vmlinux text data bss dec hex filename 70648396 21668938 17985540 110302874 693169a vmlinux while with patch: size vmlinux text data bss dec hex filename 70648128 21668938 17985540 110302606 693158e vmlinux vmlinux is still reduced by 268 bytes. > > Ah, found it: > > #if defined(CONFIG_MEMORY_HOTPLUG) > #define MEM_KEEP(sec) *(.mem##sec) > #define MEM_DISCARD(sec) > #else > #define MEM_KEEP(sec) > #define MEM_DISCARD(sec) *(.mem##sec) > #endif > > in include/asm-generic/vmlinux.lds.h When CONFIG_MEMORY_HOTREMOVE is disabled, without this patch, kswapd_stop() and kcompactd_stop() are dropped after system init. But no insist in this patch. Thanks for your comment.
