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

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

On Wed, Apr 14, 2010 at 7:07 PM, Mel Gorman <mel@csn.ul.ie> wrote:
> On Wed, Apr 14, 2010 at 07:01:47PM +0900, Minchan Kim wrote:
>> >> >>> > 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.
>>
>
> Beat in mind that uninlining can slightly increase the stack usage in some
> cases because arguments, return addresses and the like have to be pushed
> onto the stack. Inlining or unlining is only the answer when it reduces the
> number of stack variables that exist at any given time.

Yes. I totally have missed it.
Thanks, Mel.

-- 
Kind regards,
Minchan Kim

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