[Crash-utility] Re: [External Mail]Re: [BUG FIXED]fix bug of CACHED in kmem -i show memory

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Hi kazu:


1. I know that kernel have nr_swapper_spaces since kernel 4.11 which brought into kernel with struct address_space *swapper_spaces[]

my team think GKI vmlinux did not have nr_swapper_spaces this symbol, may due to compile rule changed in AOSP code.

we will try to find the root cause of vmlinux without symbol name nr_swappera_space.


     >> RELEASE: 6.1.25-android14-11-maybe-dirty-qki-consolidate
     >> crash> nr_swapper_spaces
     >> crash: command not found: nr_swapper_spaces

2. I printf log of crash when execute kmem -i, it run into branch of "symbol_exists("swapper_spaces")", also can not find nr_swapper_spaces


if (symbol_exists("nr_swapper_spaces") {

    ......

} else if (symbol_exists("swapper_spaces") {

    ......

} else if (symbol_exists("swapper_space") {

    ......

}


3. using my patch, it can fix output log of kmem -i which CACHED show not right.


Fix before:
crash> kmem -i
                 PAGES        TOTAL      PERCENTAGE
    TOTAL MEM  2854115      10.9 GB         ----
         FREE   169699     662.9 MB    5% of TOTAL MEM
         USED  2684416      10.2 GB   94% of TOTAL MEM
       SHARED   891094       3.4 GB   31% of TOTAL MEM
      BUFFERS      329       1.3 MB    0% of TOTAL MEM
       CACHED  873327085626  3331478.4 GB  30598875% of TOTAL MEM
         SLAB   230128     898.9 MB    8% of TOTAL MEM

Fix after:
crash> kmem -i
                 PAGES        TOTAL      PERCENTAGE
    TOTAL MEM  2854115      10.9 GB         ----
         FREE   169699     662.9 MB    5% of TOTAL MEM
         USED  2684416      10.2 GB   94% of TOTAL MEM
       SHARED   891094       3.4 GB   31% of TOTAL MEM
      BUFFERS      329       1.3 MB    0% of TOTAL MEM
       CACHED  1729018       6.6 GB   60% of TOTAL MEM
         SLAB   230128     898.9 MB    8% of TOTAL MEM


I think crash tools without my patch, maybe miss some situation like this which symbol miss in kenrel vmlinux.
I think that using both branch of symbol_exist("nr_swapper_spaces") and symbol_exists("swapper_spaces") means to double check
the situation of all kinds of kernel and vmlinux. 
It seen that bring my patch can deal with more unusual situation and make crash tool more compatible.


Thanks!
Best Regards


From: HAGIO KAZUHITO(?尾 一仁) <k-hagio-ab@xxxxxxx>
Sent: Friday, December 1, 2023 3:08:03 PM
To: 薛国伦; devel@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: Lianbo Jiang
Subject: Re: [External Mail]Re: [BUG FIXED]fix bug of CACHED in kmem -i show memory
 
[外部邮件] 此邮件来源于小米公司外部,请谨慎处理。若对邮件安全性存疑,请将邮件转发给misec@xxxxxxxxxx进行反馈

On 2023/11/30 22:05, 薛国伦 wrote:
> Hi kazu:
>
>
> 1. I found that vmlinux of kernel-6.1 did not have symbol nr_swapper_spaces but only have swapper_spaces
>
> Also check in GKI vmlinux, can not find nr_swapper_spaces

Hmm, upstream kernel 6.1 has it.

$ git show v6.1:mm/swap_state.c

struct address_space *swapper_spaces[MAX_SWAPFILES] __read_mostly;
static unsigned int nr_swapper_spaces[MAX_SWAPFILES] __read_mostly;

>
> It may have some problem in symbol of nr_swapper_spaces
>
>
> 2. I think that crash tools will check nr_swapper_spaces first and then check *swapper_spaces, swaper_space[] last.
>
> so first check nr_swapper_spaces not found, crash tool can use *swapper_spaces to enhance compatibility.
>
> The patch i send can resolve this situation which nr_swapper_spaces symbols can not found.

But I cannot determine whether your patch is correct and should be
applied, without kernel patches or the cause of no nr_swapper_spaces.
Could you please find the information (e.g. links) of the related kernel
patches?

Thanks,
Kazu
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