Date:   Wed, 27 Apr 2022 21:22:32 +1200
From:   Barry Song <21cnbao@...il.com>
To:     Rongwei Wang <rongwei.wang@...ux.alibaba.com>
Cc:     sj@...nel.org, Andrew Morton <akpm@...ux-foundation.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>, shuah@...nel.org,
        brendanhiggins@...gle.com, foersleo@...zon.de, sieberf@...zon.com,
        Shakeel Butt <shakeelb@...gle.com>, sjpark@...zon.de,
        tuhailong@...il.com, Song Jiang <sjiang88@...il.com>,
        张诗明(Simon Zhang) 
        <zhangshiming@...o.com>,
        李培锋(wink) <lipeifeng@...o.com>,
        xhao@...ux.alibaba.com
Subject: Re: DAMON VA regions don't split on an large Android APP

On Wed, Apr 27, 2022 at 7:44 PM Barry Song <21cnbao@...il.com> wrote:
>
> On Wed, Apr 27, 2022 at 6:56 PM Rongwei Wang
> <rongwei.wang@...ux.alibaba.com> wrote:
> >
> >
> >
> > On 4/27/22 7:19 AM, Barry Song wrote:
> > > Hi SeongJae & Andrew,
> > > (also Cc-ed main damon developers)
> > > On an Android phone, I tried to use the DAMON vaddr monitor and found
> > > that vaddr regions don't split well on large Android Apps though
> > > everything works well on native Apps.
> > >
> > > I have tried the below two cases on an Android phone with 12GB memory
> > > and snapdragon 888 CPU.
> > > 1. a native program with small memory working set  as below,
> > > #define size (1024*1024*100)
> > > main()
> > > {
> > >          volatile int *p = malloc(size);
> > >          memset(p, 0x55, size);
> > >
> > >          while(1) {
> > >                  int i;
> > >                  for (i = 0; i < size / 4; i++)
> > >                          (void)*(p + i);
> > >                  usleep(1000);
> > >
> > >                  for (i = 0; i < size / 16; i++)
> > >                          (void)*(p + i);
> > >                  usleep(1000);
> > >
> > >          }
> > > }
> > > For this application, the Damon vaddr monitor works very well.
> > > I have modified monitor.py in the damo userspace tool a little bit to
> > > show the raw data getting from the kernel.
> > > Regions can split decently on this kind of applications, a typical raw
> > > data is as below,
> > >
> > > monitoring_start:             2.224 s
> > > monitoring_end:               2.329 s
> > > monitoring_duration:       104.336 ms
> > > target_id: 0
> > > nr_regions: 24
> > > 005fb37b2000-005fb734a000(  59.594 MiB): 0
> > > 005fb734a000-005fbaf95000(  60.293 MiB): 0
> > > 005fbaf95000-005fbec0b000(  60.461 MiB): 0
> > > 005fbec0b000-005fc2910000(  61.020 MiB): 0
> > > 005fc2910000-005fc6769000(  62.348 MiB): 0
> > > 005fc6769000-005fca33f000(  59.836 MiB): 0
> > > 005fca33f000-005fcdc8b000(  57.297 MiB): 0
> > > 005fcdc8b000-005fd115a000(  52.809 MiB): 0
> > > 005fd115a000-005fd45bd000(  52.387 MiB): 0
> > > 007661c59000-007661ee4000(   2.543 MiB): 2
> > > 007661ee4000-0076623e4000(   5.000 MiB): 3
> > > 0076623e4000-007662837000(   4.324 MiB): 2
> > > 007662837000-0076630f1000(   8.727 MiB): 3
> > > 0076630f1000-007663494000(   3.637 MiB): 2
> > > 007663494000-007663753000(   2.746 MiB): 1
> > > 007663753000-007664251000(  10.992 MiB): 3
> > > 007664251000-0076666fd000(  36.672 MiB): 2
> > > 0076666fd000-007666e73000(   7.461 MiB): 1
> > > 007666e73000-007667c89000(  14.086 MiB): 2
> > > 007667c89000-007667f97000(   3.055 MiB): 0
> > > 007667f97000-007668112000(   1.480 MiB): 1
> > > 007668112000-00766820f000(1012.000 KiB): 0
> > > 007ff27b7000-007ff27d6000( 124.000 KiB): 0
> > > 007ff27d6000-007ff27d8000(   8.000 KiB): 8
> > >
> > > 2. a large Android app like Asphalt 9
> > > For this case, basically regions can't split very well, but monitor
> > > works on small vma:
> > >
> > > monitoring_start:             2.220 s
> > > monitoring_end:               2.318 s
> > > monitoring_duration:        98.576 ms
> > > target_id: 0
> > > nr_regions: 15
> > > 000012c00000-0001c301e000(   6.754 GiB): 0
> > > 0001c301e000-000371b6c000(   6.730 GiB): 0
> > > 000371b6c000-000400000000(   2.223 GiB): 0
> > > 005c6759d000-005c675a2000(  20.000 KiB): 0
> > > 005c675a2000-005c675a3000(   4.000 KiB): 3
> > > 005c675a3000-005c675a7000(  16.000 KiB): 0
> > > 0072f1e14000-0074928d4000(   6.510 GiB): 0
> > > 0074928d4000-00763c71f000(   6.655 GiB): 0
> > > 00763c71f000-0077e863e000(   6.687 GiB): 0
> > > 0077e863e000-00798e214000(   6.590 GiB): 0
> > > 00798e214000-007b0e48a000(   6.002 GiB): 0
> > > 007b0e48a000-007c62f00000(   5.323 GiB): 0
> > > 007c62f00000-007defb19000(   6.199 GiB): 0
> > > 007defb19000-007f794ef000(   6.150 GiB): 0
> > > 007f794ef000-007fe8f53000(   1.745 GiB): 0
> > >
> > > As you can see, we have some regions which are very very big and they
> > > are losing the chance to be splitted. But
> > > Damon can still monitor memory access for those small VMA areas very well like:
> > > 005c675a2000-005c675a3000(   4.000 KiB): 3
> > Hi, Barry
> >
> > Actually, we also had found the same problem in redis by ourselves
> > tool[1]. The DAMON can not split the large anon VMA well, and the anon
> > VMA has 10G~20G memory. I guess the whole region doesn't have sufficient
> > hot areas to been monitored or found by DAMON, likes one or more address
> > choose by DAMON not been accessed during sample period.
>
> Hi Rongwei,
> Thanks  for your comments and thanks for sharing your tools.
>
> I guess the cause might be:
> in case a region is very big like 10GiB, we have only 1MiB hot pages
> in this large region.
> damon will randomly pick one page to sample, but the page has only
> 1MiB/10GiB, thus
> less than 1/10000 chance to hit the hot 1MiB. so probably we need
> 10000 sample periods
> to hit the hot 1MiB in order to split this large region?
>
> @SeongJae, please correct me if I am wrong.
>
> >
> > I'm not sure whether sets init_regions can deal with the above problem,
> > or dynamic choose one or limited number VMA to monitor.
> >
>
> I won't set a limited number of VMA as this will make the damon too hard to use
> as nobody wants to make such complex operations, especially an Android
> app might have more than 8000 VMAs.
>
> I agree init_regions might be the right place to enhance the situation.
>
> > I'm not sure, just share my idea.
> >
> > [1] https://github.com/aliyun/data-profile-tools.git
>
> I suppose this tool is based on damon? How do you finally resolve the problem
> that large anon VMAs can't be splitted?
> Anyway, I will give your tool a try.

Unfortunately, data-profile-tools.git doesn't build on aarch64 ubuntu
though autogen.sh
runs successfully.

/usr/bin/ld: ./.libs/libdatop.a(disp.o): in function `cons_handler':
/root/data-profile-tools/src/disp.c:625: undefined reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/disp.c:625: undefined
reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/disp.c:625: undefined
reference to `wgetch'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_win_create':
/root/data-profile-tools/src/reg.c:108: undefined reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:108: undefined
reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:108: undefined
reference to `subwin'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_erase':
/root/data-profile-tools/src/reg.c:161: undefined reference to `werase'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_refresh':
/root/data-profile-tools/src/reg.c:171: undefined reference to `wrefresh'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_refresh_nout':
/root/data-profile-tools/src/reg.c:182: undefined reference to `wnoutrefresh'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_update_all':
/root/data-profile-tools/src/reg.c:191: undefined reference to `doupdate'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_win_destroy':
/root/data-profile-tools/src/reg.c:200: undefined reference to `delwin'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_line_write':
/root/data-profile-tools/src/reg.c:226: undefined reference to `mvwprintw'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:230: undefined
reference to `wattr_off'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:217: undefined
reference to `wattr_on'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_highlight_write':
/root/data-profile-tools/src/reg.c:245: undefined reference to `wattr_on'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:255: undefined
reference to `wattr_off'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:252: undefined
reference to `mvwprintw'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:255: undefined
reference to `wattr_off'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_curses_fini':
/root/data-profile-tools/src/reg.c:367: undefined reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:367: undefined
reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:367: undefined
reference to `wclear'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:368: undefined
reference to `wrefresh'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:369: undefined
reference to `endwin'
/usr/bin/ld: ./.libs/libdatop.a(reg.o): in function `reg_curses_init':
/root/data-profile-tools/src/reg.c:382: undefined reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:381: undefined
reference to `initscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:382: undefined
reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:382: undefined
reference to `wrefresh'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:383: undefined
reference to `use_default_colors'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:384: undefined
reference to `start_color'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:385: undefined
reference to `keypad'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:386: undefined
reference to `nonl'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:387: undefined
reference to `cbreak'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:388: undefined
reference to `noecho'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:389: undefined
reference to `curs_set'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:401: undefined
reference to `stdscr'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:401: undefined
reference to `mvwprintw'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:403: undefined
reference to `mvwprintw'
/usr/bin/ld: /root/data-profile-tools/src/reg.c:405: undefined
reference to `wrefresh'
collect2: error: ld returned 1 exit status
make[1]: *** [Makefile:592: datop] Error 1
make[1]: Leaving directory '/root/data-profile-tools'
make: *** [Makefile:438: all] Error 2

>
> > >
> > > Typical characteristics of a large Android app is that it has
> > > thousands of vma and very large virtual address spaces:
> > > ~/damo # pmap 2550 | wc -l
> > > 8522
> > >
> > > ~/damo # pmap 2550
> > > ...
> > > 0000007992bbe000      4K r----   [ anon ]
> > > 0000007992bbf000     24K rw---   [ anon ]
> > > 0000007fe8753000      4K -----   [ anon ]
> > > 0000007fe8754000   8188K rw---   [ stack ]
> > >   total         36742112K
> > >
> > > Because the whole vma list is too long, I have put the list here for
> > > you to download:
> > > wget http://www.linuxep.com/patches/android-app-vmas
> > >
> > > I can reproduce this problem on other Apps like youtube as well.
> > > I suppose we need to boost the algorithm of splitting regions for this
> > > kind of application.
> > > Any thoughts?
> > >
>
> Thanks
> Barry

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