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Message-ID: <20110418081808.GA10374@localhost>
Date: Mon, 18 Apr 2011 16:18:08 +0800
From: Wu Fengguang <fengguang.wu@...el.com>
To: "sedat.dilek@...il.com" <sedat.dilek@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Jan Kara <jack@...e.cz>,
Christoph Hellwig <hch@....de>,
Trond Myklebust <Trond.Myklebust@...app.com>,
Dave Chinner <david@...morbit.com>,
Theodore Ts'o <tytso@....edu>,
Chris Mason <chris.mason@...cle.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Mel Gorman <mel@....ul.ie>, Rik van Riel <riel@...hat.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
Greg Thelen <gthelen@...gle.com>,
Minchan Kim <minchan.kim@...il.com>,
Vivek Goyal <vgoyal@...hat.com>,
Andrea Righi <arighi@...eler.com>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
linux-mm <linux-mm@...ck.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/12] IO-less dirty throttling v7
> Unfortunately, this "v2" patch still breaks with gcc-4.6 here:
>
> LD .tmp_vmlinux1
> mm/built-in.o: In function `calc_period_shift.part.10':
> page-writeback.c:(.text+0x6458): undefined reference to `____ilog2_NaN'
> make[4]: *** [.tmp_vmlinux1] Error 1
>
> My patchset against next-20110415 looks like this:
>
> (+) OK writeback-dirty-throttling-v7/writeback-dirty-throttling-v7.patch
> (+) OK writeback-dirty-throttling-post-v7/0001-writeback-i386-compile-fix.patch
> (+) OK writeback-dirty-throttling-post-v7/0002-writeback-quick-CONFIG_BLK_DEV_THROTTLING-n-compile-.patch
> (+) OK writeback-dirty-throttling-post-v7/0003-Revert-writeback-scale-dirty-proportions-period-with.patch
> (+) OK writeback-dirty-throttling-v7-fix/writeback-scale-dirty-proportions-period-with-writeout-bandwidth-v2.patch
>
> Attached are the disasm of mm/page-writeback.o (v2, gcc-4.6) and the
> disasm of yesterday's experiments with gcc-4.5.
>
> [ gcc-4.5 ]
>
> 00006574 <calc_period_shift>:
> 6574: a1 90 00 00 00 mov 0x90,%eax 6575:
> R_386_32 default_backing_dev_info
> 6579: 55 push %ebp
> 657a: 89 e5 mov %esp,%ebp
> 657c: e8 02 f8 ff ff call 5d83 <__ilog2_u32>
> 6581: 5d pop %ebp
> 6582: 83 c0 02 add $0x2,%eax
> 6585: c3 ret
gcc-4.5 is generating the right code, while the below silly macro
expansion seems like __builtin_constant_p(n) wrongly evaluating to true.
I wonder if the attached patch will workaround the gcc's bug. It adds a
local variable in calc_period_shift() for passing to ilog2().
Thanks,
Fengguang
> [ gcc-4.6 ]
>
> 000008c9 <calc_period_shift.part.10>:
> 8c9: 8b 15 90 00 00 00 mov 0x90,%edx 8cb:
> R_386_32 default_backing_dev_info
> 8cf: 55 push %ebp
> 8d0: 89 e5 mov %esp,%ebp
> 8d2: 85 d2 test %edx,%edx
> 8d4: 0f 88 46 01 00 00 js a20
> <calc_period_shift.part.10+0x157>
> 8da: f7 c2 00 00 00 40 test $0x40000000,%edx
> 8e0: b8 20 00 00 00 mov $0x20,%eax
> 8e5: 0f 85 3a 01 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 8eb: f7 c2 00 00 00 20 test $0x20000000,%edx
> 8f1: b0 1f mov $0x1f,%al
> 8f3: 0f 85 2c 01 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 8f9: f7 c2 00 00 00 10 test $0x10000000,%edx
> 8ff: b0 1e mov $0x1e,%al
> 901: 0f 85 1e 01 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 907: f7 c2 00 00 00 08 test $0x8000000,%edx
> 90d: b0 1d mov $0x1d,%al
> 90f: 0f 85 10 01 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 915: f7 c2 00 00 00 04 test $0x4000000,%edx
> 91b: b0 1c mov $0x1c,%al
> 91d: 0f 85 02 01 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 923: f7 c2 00 00 00 02 test $0x2000000,%edx
> 929: b0 1b mov $0x1b,%al
> 92b: 0f 85 f4 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 931: f7 c2 00 00 00 01 test $0x1000000,%edx
> 937: b0 1a mov $0x1a,%al
> 939: 0f 85 e6 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 93f: f7 c2 00 00 80 00 test $0x800000,%edx
> 945: b0 19 mov $0x19,%al
> 947: 0f 85 d8 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 94d: f7 c2 00 00 40 00 test $0x400000,%edx
> 953: b0 18 mov $0x18,%al
> 955: 0f 85 ca 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 95b: f7 c2 00 00 20 00 test $0x200000,%edx
> 961: b0 17 mov $0x17,%al
> 963: 0f 85 bc 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 969: f7 c2 00 00 10 00 test $0x100000,%edx
> 96f: b0 16 mov $0x16,%al
> 971: 0f 85 ae 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 977: f7 c2 00 00 08 00 test $0x80000,%edx
> 97d: b0 15 mov $0x15,%al
> 97f: 0f 85 a0 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 985: f7 c2 00 00 04 00 test $0x40000,%edx
> 98b: b0 14 mov $0x14,%al
> 98d: 0f 85 92 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 993: f7 c2 00 00 02 00 test $0x20000,%edx
> 999: b0 13 mov $0x13,%al
> 99b: 0f 85 84 00 00 00 jne a25
> <calc_period_shift.part.10+0x15c>
> 9a1: f7 c2 00 00 01 00 test $0x10000,%edx
> 9a7: b0 12 mov $0x12,%al
> 9a9: 75 7a jne a25
> <calc_period_shift.part.10+0x15c>
> 9ab: f6 c6 80 test $0x80,%dh
> 9ae: b0 11 mov $0x11,%al
> 9b0: 75 73 jne a25
> <calc_period_shift.part.10+0x15c>
> 9b2: f6 c6 40 test $0x40,%dh
> 9b5: b0 10 mov $0x10,%al
> 9b7: 75 6c jne a25
> <calc_period_shift.part.10+0x15c>
> 9b9: f6 c6 20 test $0x20,%dh
> 9bc: b0 0f mov $0xf,%al
> 9be: 75 65 jne a25
> <calc_period_shift.part.10+0x15c>
> 9c0: f6 c6 10 test $0x10,%dh
> 9c3: b0 0e mov $0xe,%al
> 9c5: 75 5e jne a25
> <calc_period_shift.part.10+0x15c>
> 9c7: f6 c6 08 test $0x8,%dh
> 9ca: b0 0d mov $0xd,%al
> 9cc: 75 57 jne a25
> <calc_period_shift.part.10+0x15c>
> 9ce: f6 c6 04 test $0x4,%dh
> 9d1: b0 0c mov $0xc,%al
> 9d3: 75 50 jne a25
> <calc_period_shift.part.10+0x15c>
> 9d5: f6 c6 02 test $0x2,%dh
> 9d8: b0 0b mov $0xb,%al
> 9da: 75 49 jne a25
> <calc_period_shift.part.10+0x15c>
> 9dc: f6 c6 01 test $0x1,%dh
> 9df: b0 0a mov $0xa,%al
> 9e1: 75 42 jne a25
> <calc_period_shift.part.10+0x15c>
> 9e3: f6 c2 80 test $0x80,%dl
> 9e6: b0 09 mov $0x9,%al
> 9e8: 75 3b jne a25
> <calc_period_shift.part.10+0x15c>
> 9ea: f6 c2 40 test $0x40,%dl
> 9ed: b0 08 mov $0x8,%al
> 9ef: 75 34 jne a25
> <calc_period_shift.part.10+0x15c>
> 9f1: f6 c2 20 test $0x20,%dl
> 9f4: b0 07 mov $0x7,%al
> 9f6: 75 2d jne a25
> <calc_period_shift.part.10+0x15c>
> 9f8: f6 c2 10 test $0x10,%dl
> 9fb: b0 06 mov $0x6,%al
> 9fd: 75 26 jne a25
> <calc_period_shift.part.10+0x15c>
> 9ff: f6 c2 08 test $0x8,%dl
> a02: b0 05 mov $0x5,%al
> a04: 75 1f jne a25
> <calc_period_shift.part.10+0x15c>
> a06: f6 c2 04 test $0x4,%dl
> a09: b0 04 mov $0x4,%al
> a0b: 75 18 jne a25
> <calc_period_shift.part.10+0x15c>
> a0d: f6 c2 02 test $0x2,%dl
> a10: b0 03 mov $0x3,%al
> a12: 75 11 jne a25
> <calc_period_shift.part.10+0x15c>
> a14: 80 e2 01 and $0x1,%dl
> a17: b0 02 mov $0x2,%al
> a19: 75 0a jne a25
> <calc_period_shift.part.10+0x15c>
> a1b: e8 fc ff ff ff call a1c
> <calc_period_shift.part.10+0x153> a1c: R_386_PC32 ____ilog2_NaN
> a20: b8 21 00 00 00 mov $0x21,%eax
> a25: 5d pop %ebp
> a26: c3 ret
>
> 00000a27 <calc_period_shift>:
> a27: 55 push %ebp
> a28: 83 ca ff or $0xffffffff,%edx
> a2b: 89 e5 mov %esp,%ebp
> a2d: 0f bd 05 90 00 00 00 bsr 0x90,%eax a30:
> R_386_32 default_backing_dev_info
> a34: 0f 44 c2 cmove %edx,%eax
> a37: 5d pop %ebp
> a38: 83 c0 02 add $0x2,%eax
> a3b: c3 ret
>
> - EOT -
>
> - Sedat -
View attachment "writeback-adaptive-proportions-shift.patch" of type "text/x-diff" (2281 bytes)
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