Heres an old email I dug up. It was running an sdet like thing.
Anton
Date: Fri, 26 Jul 2002 06:32:52 +1000
From: Anton Blanchard <anton@samba.org>
To: Andrew Morton <akpm@zip.com.au>
Cc: Rik van Riel <riel@conectiva.com.br>,
William Lee Irwin III <wli@holomorphy.com>,
"Martin J. Bligh" <Martin.Bligh@us.ibm.com>
Subject: Re: [anton@samba.org: raw data] (fwd)
> > 26274 .page_remove_rmap
> > 19059 .page_add_rmap
> > 13378 .save_remaining_regs
> > 11126 .page_cache_release
> > 10031 .clear_user_page
> > 9616 .copy_page
> > 9539 .do_page_fault
> > 8876 .pSeries_insert_hpte
> > 8488 .pSeries_flush_hash_range
> > 8106 .find_get_page
> > 7496 .lru_cache_add
> > 6789 .copy_page_range
> > 6177 .zap_pte_range
>
> Holy cow.
Here are the results when I embedded a spinlock in the page struct.
19624 .page_remove_rmap
15682 .save_remaining_regs
13835 .page_cache_release
12827 .zap_pte_range
12624 .do_page_fault
12390 .copy_page_range
10908 .pSeries_insert_hpte
10492 .pSeries_flush_hash_range
9219 .find_get_page
8879 .page_add_rmap
7482 .copy_page
6672 .kmem_cache_free
5672 .kmem_cache_alloc
page_add_rmap has dropped an awful lot. I need to check that its
actually the change from bitop spinlock to regular spinlock and not the
increase in page struct size (which might be reduce cacheline sharing
between adjacent mem_map entries).
As expected the difference between page_add_rmap and page_remove_rmap
looks to be the linked list walk. From the profile below, lock
aquisition is 15% and list walking is about 40% of the function.
The two things that seem to help us here are:
1. Half as many atomic operations. The lock drop is a simple store
instead of an atomic sequence needed to avoid changing the other bits in
the flags word.
2. Not completing the atomic sequence when we know we arent going to get
the lock. The spinlock backs off to loads when someone else has the
lock, avoiding the costly store with reservation. Perhaps I should make
our bitops do a similar check so we do a load with reservation and
jump straight out if the bit is set. Im guessing you cant do the same on
intel.
Anton
00094864 .page_remove_rmap 19784
0.3 c000000000094864 std r30,-16(r1)
0.2 c000000000094868 mflr r0
0.0 c00000000009486c ld r30,-18960(r2)
0.0 c000000000094870 std r0,16(r1)
0.0 c000000000094874 subfic r0,r3,0
0.3 c000000000094878 adde r11,r0,r3
0.0 c00000000009487c subfic r10,r4,0
0.0 c000000000094880 adde r0,r10,r4
0.0 c000000000094884 std r27,-40(r1)
0.3 c000000000094888 or r0,r0,r11
0.0 c00000000009488c li r27,0
0.0 c000000000094890 std r28,-32(r1)
0.0 c000000000094894 cmpwi r0,0
0.3 c000000000094898 mr r28,r4
0.0 c00000000009489c std r29,-24(r1)
0.0 c0000000000948a0 mr r29,r3
0.0 c0000000000948a4 std r31,-8(r1)
0.3 c0000000000948a8 std r26,-48(r1)
0.0 c0000000000948ac stdu r1,-160(r1)
0.0 c0000000000948b0 lbz r9,40(r3)
0.5 c0000000000948b4 ld r8,-32752(r30)
0.0 c0000000000948b8 rldicr r9,r9,3,60
0.0 c0000000000948bc ld r10,-32744(r30)
0.0 c0000000000948c0 ldx r11,r9,r8
0.9 c0000000000948c4 ld r0,4616(r11)
0.0 c0000000000948c8 ld r9,4624(r11)
0.0 c0000000000948cc subf r0,r0,r3
0.0 c0000000000948d0 sradi r0,r0,3
1.1 c0000000000948d4 rldicl r9,r9,52,12
0.0 c0000000000948d8 mulld r0,r0,r10
0.0 c0000000000948dc add r31,r0,r9
0.0 c0000000000948e0 bne- c000000000094a34
1.6 c0000000000948e4 ld r9,-32768(r30)
0.0 c0000000000948e8 ld r0,0(r9)
0.0 c0000000000948ec cmpld r31,r0
0.0 c0000000000948f0 bge- c00000000009497c
1.1 c0000000000948f4 ld r0,40(r29)
0.0 c0000000000948f8 addi r31,r29,40
0.0 c0000000000948fc rldicl r0,r0,53,63
0.1 c000000000094900 cmpwi r0,0
0.0 c000000000094904 bne- c00000000009497c
0.7 c000000000094908 addi r11,r29,80
0.0 c00000000009490c li r9,1
0.0 c000000000094910 b c000000000094920
3.4 c000000000094914 lwzx r10,r0,r11
0.0 c000000000094918 cmpwi r10,0
0.0 c00000000009491c bne- c000000000094914
0.9 c000000000094920 lwarx r10,r0,r11
3.8 c000000000094924 cmpwi r10,0
0.0 c000000000094928 bne+ c000000000094914
0.5 c00000000009492c stwcx. r9,r0,r11
14.9 c000000000094930 bne+ c000000000094920
0.8 c000000000094934 isync
4.7 c000000000094938 ld r0,40(r29)
6.8 c00000000009493c rldicl r0,r0,48,63
0.2 c000000000094940 cmpwi r0,0
0.0 c000000000094944 beq- c0000000000949c0
0.1 c000000000094948 ld r0,64(r29)
0.0 c00000000009494c cmpd r0,r28
0.0 c000000000094950 beq- c0000000000949a4
2.4 c000000000094954 lhz r10,24(r13)
0.0 c000000000094958 ld r0,-32760(r30)
0.0 c00000000009495c rldicr r10,r10,7,56
0.1 c000000000094960 add r10,r10,r0
0.2 c000000000094964 ld r11,48(r10)
0.0 c000000000094968 addi r11,r11,-1
0.0 c00000000009496c std r11,48(r10)
0.3 c000000000094970 eieio
0.3 c000000000094974 li r0,0
0.0 c000000000094978 stw r0,80(r29)
0.0 c00000000009497c addi r1,r1,160
0.0 c000000000094980 ld r0,16(r1)
0.4 c000000000094984 ld r26,-48(r1)
0.2 c000000000094988 mtlr r0
0.0 c00000000009498c ld r27,-40(r1)
0.0 c000000000094990 ld r28,-32(r1)
0.0 c000000000094994 ld r29,-24(r1)
0.2 c000000000094998 ld r30,-16(r1)
0.0 c00000000009499c ld r31,-8(r1)
0.0 c0000000000949a0 blr
0.1 c0000000000949a4 std r27,64(r29)
0.0 c0000000000949a8 lis r0,1
0.0 c0000000000949ac ldarx r9,r0,r31
1.2 c0000000000949b0 andc r9,r9,r0
0.1 c0000000000949b4 stdcx. r9,r0,r31
1.4 c0000000000949b8 bne+ c0000000000949ac
0.1 c0000000000949bc b c000000000094954
0.8 c0000000000949c0 ld r3,64(r29)
0.0 c0000000000949c4 cmpdi r3,0
0.0 c0000000000949c8 beq+ c000000000094954
0.7 c0000000000949cc lis r26,1
1.4 c0000000000949d0 ld r0,8(r3)
0.0 c0000000000949d4 cmpd r0,r28
0.0 c0000000000949d8 beq- c0000000000949f0
38.4 c0000000000949dc mr r27,r3
0.1 c0000000000949e0 ld r3,0(r3)
0.0 c0000000000949e4 cmpdi r3,0
0.0 c0000000000949e8 bne+ c0000000000949d0
0.0 c0000000000949ec b c000000000094954
5.4 c0000000000949f0 mr r4,r27
0.0 c0000000000949f4 mr r5,r29
0.0 c0000000000949f8 bl c000000000094f14 <.pte_chain_free>
0.1 c0000000000949fc ld r3,64(r29)
0.1 c000000000094a00 ld r0,0(r3)
0.0 c000000000094a04 cmpdi r0,0
0.0 c000000000094a08 bne+ c000000000094954
0.5 c000000000094a0c ld r0,8(r3)
0.0 c000000000094a10 std r0,64(r29)
0.0 c000000000094a14 ldarx r9,r0,r31
0.2 c000000000094a18 or r9,r9,r26
0.0 c000000000094a1c stdcx. r9,r0,r31
1.3 c000000000094a20 bne+ c000000000094a14
0.1 c000000000094a24 li r4,0
0.0 c000000000094a28 li r5,0
0.0 c000000000094a2c bl c000000000094f14 <.pte_chain_free>
0.0 c000000000094a30 b c000000000094954
0.0 c000000000094a34 ld r3,-32736(r30)
0.0 c000000000094a38 li r5,172
0.0 c000000000094a3c ld r4,-32728(r30)
0.0 c000000000094a40 bl c000000000059620 <.printk>
0.0 c000000000094a44 nop
0.0 c000000000094a48 li r3,0
0.0 c000000000094a4c bl c0000000001ce80c <.xmon>
0.0 c000000000094a50 nop
0.0 c000000000094a54 b c0000000000948e4
000946f8 .page_add_rmap 9001
0.7 c0000000000946f8 std r30,-16(r1)
0.4 c0000000000946fc mflr r0
0.0 c000000000094700 ld r30,-18960(r2)
0.0 c000000000094704 std r28,-32(r1)
0.0 c000000000094708 mr r28,r4
0.5 c00000000009470c ld r11,-32768(r30)
0.1 c000000000094710 std r29,-24(r1)
0.0 c000000000094714 addi r29,r3,40
0.0 c000000000094718 std r31,-8(r1)
0.6 c00000000009471c mr r31,r3
0.0 c000000000094720 std r0,16(r1)
0.0 c000000000094724 stdu r1,-144(r1)
0.4 c000000000094728 ld r0,0(r4)
0.1 c00000000009472c ld r9,0(r11)
0.0 c000000000094730 rldicl r0,r0,48,16
0.0 c000000000094734 cmpld r0,r9
0.0 c000000000094738 bge- c0000000000947d8
10.3 c00000000009473c ld r0,40(r3)
0.0 c000000000094740 addi r9,r3,80
0.0 c000000000094744 li r11,1
0.0 c000000000094748 rldicl r0,r0,53,63
1.2 c00000000009474c cmpwi r0,0
0.0 c000000000094750 bne- c0000000000947d8
0.7 c000000000094754 b c000000000094764
4.1 c000000000094758 lwzx r0,r0,r9
0.0 c00000000009475c cmpwi r0,0
2.8 c000000000094760 bne- c000000000094758
0.6 c000000000094764 lwarx r0,r0,r9
8.9 c000000000094768 cmpwi r0,0
0.0 c00000000009476c bne+ c000000000094758
0.9 c000000000094770 stwcx. r11,r0,r9
24.6 c000000000094774 bne+ c000000000094764
1.3 c000000000094778 isync
9.7 c00000000009477c ld r9,40(r3)
10.0 c000000000094780 rldicl r9,r9,48,63
0.0 c000000000094784 cmpwi r9,0
0.0 c000000000094788 bne- c000000000094810
2.3 c00000000009478c ld r0,64(r31)
0.0 c000000000094790 lis r9,1
0.0 c000000000094794 cmpdi r0,0
0.0 c000000000094798 bne- c0000000000947f8
0.3 c00000000009479c std r28,64(r31)
0.1 c0000000000947a0 ldarx r0,r0,r29
2.8 c0000000000947a4 or r0,r0,r9
0.1 c0000000000947a8 stdcx. r0,r0,r29
2.5 c0000000000947ac bne+ c0000000000947a0
1.1 c0000000000947b0 eieio
0.9 c0000000000947b4 li r0,0
0.0 c0000000000947b8 stw r0,80(r31)
0.0 c0000000000947bc lhz r9,24(r13)
0.2 c0000000000947c0 ld r0,-32760(r30)
0.6 c0000000000947c4 rldicr r9,r9,7,56
0.0 c0000000000947c8 add r9,r9,r0
0.0 c0000000000947cc ld r10,48(r9)
0.4 c0000000000947d0 addi r10,r10,1
2.3 c0000000000947d4 std r10,48(r9)
0.0 c0000000000947d8 addi r1,r1,144
0.0 c0000000000947dc ld r0,16(r1)
0.3 c0000000000947e0 ld r28,-32(r1)
0.7 c0000000000947e4 mtlr r0
0.0 c0000000000947e8 ld r29,-24(r1)
0.0 c0000000000947ec ld r30,-16(r1)
0.0 c0000000000947f0 ld r31,-8(r1)
0.0 c0000000000947f4 blr
1.2 c0000000000947f8 bl c000000000094f98 <.pte_chain_alloc>
0.4 c0000000000947fc std r28,8(r3)
1.0 c000000000094800 ld r0,64(r31)
0.0 c000000000094804 std r0,0(r3)
0.0 c000000000094808 std r3,64(r31)
0.0 c00000000009480c b c0000000000947b0
0.4 c000000000094810 bl c000000000094f98 <.pte_chain_alloc>
0.1 c000000000094814 li r0,0
0.0 c000000000094818 ld r11,64(r31)
0.0 c00000000009481c lis r9,1
0.2 c000000000094820 std r0,0(r3)
0.1 c000000000094824 std r11,8(r3)
0.0 c000000000094828 std r3,64(r31)
0.2 c00000000009482c ldarx r0,r0,r29
0.4 c000000000094830 andc r0,r0,r9
0.0 c000000000094834 stdcx. r0,r0,r29
3.3 c000000000094838 bne+ c00000000009482c
0.3 c00000000009483c b c00000000009478c
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