Re: [PATCH] mm: disallow direct reclaim page writeback

[Minchan Kim <minchan.kim@gmail.com>]

On Wed, Apr 14, 2010 at 6:42 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Wed, 14 Apr 2010 16:19:02 +0900
> Minchan Kim <minchan.kim@gmail.com> wrote:
>
>> On Wed, Apr 14, 2010 at 3:13 PM, Minchan Kim <minchan.kim@gmail.com> wrote:
>> > On Wed, Apr 14, 2010 at 2:54 PM, KOSAKI Motohiro
>> > <kosaki.motohiro@jp.fujitsu.com> wrote:
>> >>> On Wed, Apr 14, 2010 at 01:59:45PM +0900, KAMEZAWA Hiroyuki wrote:
>> >>> > On Wed, 14 Apr 2010 11:40:41 +1000
>> >>> > Dave Chinner <david@fromorbit.com> wrote:
>> >>> >
>> >>> > >  50)     3168      64   xfs_vm_writepage+0xab/0x160 [xfs]
>> >>> > >  51)     3104     384   shrink_page_list+0x65e/0x840
>> >>> > >  52)     2720     528   shrink_zone+0x63f/0xe10
>> >>> >
>> >>> > A bit OFF TOPIC.
>> >>> >
>> >>> > Could you share disassemble of shrink_zone() ?
>> >>> >
>> >>> > In my environ.
>> >>> > 00000000000115a0 <shrink_zone>:
>> >>> >    115a0:       55                      push   %rbp
>> >>> >    115a1:       48 89 e5                mov    %rsp,%rbp
>> >>> >    115a4:       41 57                   push   %r15
>> >>> >    115a6:       41 56                   push   %r14
>> >>> >    115a8:       41 55                   push   %r13
>> >>> >    115aa:       41 54                   push   %r12
>> >>> >    115ac:       53                      push   %rbx
>> >>> >    115ad:       48 83 ec 78             sub    $0x78,%rsp
>> >>> >    115b1:       e8 00 00 00 00          callq  115b6 <shrink_zone+0x16>
>> >>> >    115b6:       48 89 75 80             mov    %rsi,-0x80(%rbp)
>> >>> >
>> >>> > disassemble seems to show 0x78 bytes for stack. And no changes to %rsp
>> >>> > until retrun.
>> >>>
>> >>> I see the same. I didn't compile those kernels, though. IIUC,
>> >>> they were built through the Ubuntu build infrastructure, so there is
>> >>> something different in terms of compiler, compiler options or config
>> >>> to what we are both using. Most likely it is the compiler inlining,
>> >>> though Chris's patches to prevent that didn't seem to change the
>> >>> stack usage.
>> >>>
>> >>> I'm trying to get a stack trace from the kernel that has shrink_zone
>> >>> in it, but I haven't succeeded yet....
>> >>
>> >> I also got 0x78 byte stack usage. Umm.. Do we discussed real issue now?
>> >>
>> >
>> > In my case, 0x110 byte in 32 bit machine.
>> > I think it's possible in 64 bit machine.
>> >
>> > 00001830 <shrink_zone>:
>> >    1830:       55                      push   %ebp
>> >    1831:       89 e5                   mov    %esp,%ebp
>> >    1833:       57                      push   %edi
>> >    1834:       56                      push   %esi
>> >    1835:       53                      push   %ebx
>> >    1836:       81 ec 10 01 00 00       sub    $0x110,%esp
>> >    183c:       89 85 24 ff ff ff       mov    %eax,-0xdc(%ebp)
>> >    1842:       89 95 20 ff ff ff       mov    %edx,-0xe0(%ebp)
>> >    1848:       89 8d 1c ff ff ff       mov    %ecx,-0xe4(%ebp)
>> >    184e:       8b 41 04                mov    0x4(%ecx)
>> >
>> > my gcc is following as.
>> >
>> > barrios@barriostarget:~/mmotm$ gcc -v
>> > Using built-in specs.
>> > Target: i486-linux-gnu
>> > Configured with: ../src/configure -v --with-pkgversion='Ubuntu
>> > 4.3.3-5ubuntu4'
>> > --with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
>> > --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
>> > --enable-shared --with-system-zlib --libexecdir=/usr/lib
>> > --without-included-gettext --enable-threads=posix --enable-nls
>> > --with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3
>> > --enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc
>> > --enable-mpfr --enable-targets=all --with-tune=generic
>> > --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu
>> > --target=i486-linux-gnu
>> > Thread model: posix
>> > gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4)
>> >
>> >
>> > Is it depends on config?
>> > I attach my config.
>>
>> I changed shrink list by noinline_for_stack.
>> The result is following as.
>>
>>
>> 00001fe0 <shrink_zone>:
>>     1fe0:       55                      push   %ebp
>>     1fe1:       89 e5                   mov    %esp,%ebp
>>     1fe3:       57                      push   %edi
>>     1fe4:       56                      push   %esi
>>     1fe5:       53                      push   %ebx
>>     1fe6:       83 ec 4c                sub    $0x4c,%esp
>>     1fe9:       89 45 c0                mov    %eax,-0x40(%ebp)
>>     1fec:       89 55 bc                mov    %edx,-0x44(%ebp)
>>     1fef:       89 4d b8                mov    %ecx,-0x48(%ebp)
>>
>> 0x110 -> 0x4c.
>>
>> Should we have to add noinline_for_stack for shrink_list?
>>
>
> Hmm. about shirnk_zone(), I don't think uninlining functions directly called
> by shrink_zone() can be a help.
> Total stack size of call-chain will be still big.

Absolutely.
But above 500 byte usage is one of hogger and uninlining is not
critical about reclaim performance. So I think we don't get any lost
than gain.

But I don't get in a hurry. adhoc approach is not good.
I hope when Mel tackles down consumption of stack in reclaim path, he
modifies this part, too.

Thanks.

> Thanks,
> -Kame
>
>
>



-- 
Kind regards,
Minchan Kim