lkml.org 
[lkml]   [2018]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patches in this message
/
From
SubjectRe: [PATCH v2 7/7] swap, put_swap_page: Share more between huge/normal code path
Date
Dave Hansen <dave.hansen@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

\
 
 \ /
  Last update: 2018-07-18 04:57    [W:0.047 / U:0.244 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site