7:27 a.m.
Hi,Dave & hatayama
I made two patchs in crash-utility and gcore to support zram decompress
1.In crash-utility,I add patch in readmem to support zram decompression, readmem interface
automatically recognizes and decompresses zram data.
There are some limitations to zram support,only support lzo decompress,kernel support
lzo,lz4,lz4hc,842,zstd,but lzo is default.
use "rd" command also read data even if mapping to zram
[without patch]
crash> rd 144fc000 2
rd: invalid user virtual address: 144fc000 type: "64-bit UVADDR"
[with patch]
crash> rd 144fc000 2
144fc000: 06ecdc6b06ecb280 06f027f906eebebe ....k........'..
2.In gcore, I have to make a small change ,change parameter of readmem from PHYADDR to
UVADDR, other work will be done by crash
Please help review.
Thanks
-----邮件原件-----
发件人: Dave Anderson <anderson(a)redhat.com>
发送时间: 2020年4月2日 0:29
收件人: 赵乾利 <zhaoqianli(a)xiaomi.com>
抄送: d hatayama <d.hatayama(a)fujitsu.com>; Discussion list for crash utility usage,
maintenance and development <crash-utility(a)redhat.com>
主题: Re: [External Mail]Re: [Crash-utility] zram decompress support for
gcore/crash-utility
----- Original Message -----
Hi,Dave
Zram is a virtual device,it simulated as a block device,it's part of
memroy/ramdump,just enable CONFIG_ZRAM,no other settings needed.
you can refer to drivers/block/zram/zram_drv.c driver calling
zram_meta_alloc to alloc memory from RAM.
We want to be able to access these zram page like a normal page.
I understand all that. I'm just curious how makedumpfile will handle/filter the
physical RAM pages that make up the zram block device.
Anyway, send a patch and I'll take a look.
Dave
________________________________________
From: Dave Anderson <anderson(a)redhat.com>
Sent: Wednesday, April 1, 2020 23:24
To: 赵乾利
Cc: d hatayama; Discussion list for crash utility usage, maintenance
and development
Subject: Re: [External Mail]Re: [Crash-utility] zram decompress
support for gcore/crash-utility
----- Original Message -----
> Hi,Dave
> zram is same with other swap device,but every swaped page will be
> compressed then saved to another memory address.
> The process is same with the common swap device,non-swap just a
> normal user address,pgd and mmu will translate to phy address
>
> please refer to below information:
> crash> vm -p
> PID: 1565 TASK: ffffffe1fce32d00 CPU: 7 COMMAND: "system_server"
> MM PGD RSS TOTAL_VM
> ffffffe264431c00 ffffffe1f54ad000 528472k 9780384k
> VMA START END FLAGS FILE
> ffffffe0ea401300 12c00000 12e00000 100073
> VIRTUAL PHYSICAL
> ...
> 144fc000 SWAP: /dev/block/zram0 OFFSET: 236750
> ...
> 1738e000 SWAP: /dev/block/zram0 OFFSET: 73426
> 1738f000 21aa2c000
> 17390000 1c3308000
> 17391000 SWAP: /dev/block/zram0 OFFSET: 73431
> 17392000 19c162000
> 17393000 19c132000
> 17394000 SWAP: /dev/block/zram0 OFFSET: 234576
> 17395000 19c369000
> 17396000 20b35c000
> 17397000 18011e000
> 17398000 SWAP: /dev/block/zram0 OFFSET: 73433
> 17399000 1dc3d2000
> 1739a000 1bc59f000
> 1739b000 SWAP: /dev/block/zram0 OFFSET: 73437
>
>
> crash> vtop -c 1565 144fc000
> VIRTUAL PHYSICAL
> 144fc000 (not mapped)
>
> PAGE DIRECTORY: ffffffe1f54ad000
> PGD: ffffffe1f54ad000 => 1f54ab003
> PMD: ffffffe1f54ab510 => 1f43b8003
> PTE: ffffffe1f43b87e0 => 39cce00
>
> PTE SWAP OFFSET
> 39cce00 /dev/block/zram0 236750
>
> VMA START END FLAGS FILE
> ffffffe148bafe40 144c0000 14540000 100073
>
> SWAP: /dev/block/zram0 OFFSET: 236750
Ok, so with respect to user-space virtual addresses, there is nothing
other than handling zram swap-backed memory.
So what you're proposing is that when reading user-space memory that
happens to be backed-up on a zram swap device, then the user data
could alternatively be read from the zram swap device, and presented
as if it were present in physical memory?
Are the physical RAM pages that make up the contents of a zram device
collected with a typical filtered compressed kdump? If not, what
makedumpfile -d flag is required for them to be captured?
Dave
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