Dave Hansen <dave.han...@linux.intel.com> writes: > On 07/16/2018 05:55 PM, Huang, Ying wrote: >> text data bss dec hex filename >> base: 24215 2028 340 26583 67d7 mm/swapfile.o >> unified: 24577 2028 340 26945 6941 mm/swapfile.o > > That's a bit more than I'd expect looking at the rest of the diff. Make > me wonder if we missed an #ifdef somewhere or the compiler is getting > otherwise confused. > > Might be worth a 10-minute look at the disassembly.
Dig one step deeper via 'size -A mm/swapfile.o' and diff between base and unified, --- b.s 2018-07-18 09:42:07.872501680 +0800 +++ h.s 2018-07-18 09:50:37.984499168 +0800 @@ -1,6 +1,6 @@ mm/swapfile.o : section size addr -.text 17815 0 +.text 17927 0 .data 1288 0 .bss 340 0 ___ksymtab_gpl+nr_swap_pages 8 0 @@ -26,8 +26,8 @@ .data.once 1 0 .comment 35 0 .note.GNU-stack 0 0 -.orc_unwind_ip 1380 0 -.orc_unwind 2070 0 -Total 26810 +.orc_unwind_ip 1480 0 +.orc_unwind 2220 0 +Total 27172 The total difference is same: 27172 - 26810 = 362 = 24577 - 24215. The text section difference is small: 17927 - 17815 = 112. The additional size change comes from unwinder information: (1480 + 2220) - (1380 + 2070) = 250. If the frame pointer unwinder is chosen, this cost nothing, but if the ORC unwinder is chosen, this is the real difference. For 112 text section difference, use 'objdump -t' to get symbol size and compare, --- b.od 2018-07-18 10:45:05.768483075 +0800 +++ h.od 2018-07-18 10:44:39.556483204 +0800 @@ -30,9 +30,9 @@ 00000000000000a3 cluster_list_add_tail 000000000000001e __kunmap_atomic.isra.34 000000000000018c swap_count_continued -00000000000000ac __swap_entry_free 000000000000000f put_swap_device.isra.35 00000000000000b4 inc_cluster_info_page +000000000000006f __swap_entry_free_locked 000000000000004a _enable_swap_info 0000000000000046 wait_on_page_writeback 000000000000002e inode_to_bdi @@ -53,8 +53,8 @@ 0000000000000012 __x64_sys_swapon 0000000000000011 __ia32_sys_swapon 000000000000007a get_swap_device -0000000000000032 swap_free -0000000000000035 put_swap_page +000000000000006e swap_free +0000000000000078 put_swap_page 0000000000000267 swapcache_free_entries 0000000000000058 page_swapcount 000000000000003a __swap_count @@ -64,7 +64,7 @@ 000000000000011a try_to_free_swap 00000000000001fb get_swap_pages 0000000000000098 get_swap_page_of_type -00000000000001b8 free_swap_and_cache +00000000000001e6 free_swap_and_cache 0000000000000543 try_to_unuse 000000000000000e __x64_sys_swapoff 000000000000000d __ia32_sys_swapoff The size of put_swap_page() change is small: 0x78 - 0x35 = 67. But __swap_entry_free() is inlined by compiler, which cause some code dilating. Best Regards, Huang, Ying
