linux-kernel - Re: [RFC PATCH] Add /proc/<pid>/numa

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Message-ID: <dd4c3282-03b8-7480-fea7-fecce0ea2444@oracle.com>
Date:   Thu, 13 Sep 2018 15:17:57 -0700
From:   "prakash.sangappa" <prakash.sangappa@...cle.com>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     linux-kernel@...r.kernel.org, mhocko@...nel.org,
        dave.hansen@...el.com, cl@...ux.com, khandual@...ux.vnet.ibm.com
Subject: Re: [RFC PATCH] Add /proc/<pid>/numa_vamaps for numa node information



On 09/12/2018 04:02 PM, Alexey Dobriyan wrote:
>> The /proc/pid/numa_vamaps shows mapped address ranges to numa node id
>> from where the physical pages are allocated.
> All these files make the problem with useless dentry and /proc/*/* inode
> instantiations worse (unlike top level /proc/* files which are
> tolerable).
>
>> +address-range	numa-node-id
>> +
>> +00400000-00410000 N1
>> +00410000-0047f000 N0
>> +0047f000-00480000 N2
>> +00480000-00481000 -
>> +00481000-004a0000 N0
>> +004a0000-004a2000 -
>> +004a2000-004aa000 N2
>> +004aa000-004ad000 N0
>> +004ad000-004ae000 -
> 'N' is useless data.

'N' could be dropped.

>
> Parsing with awk won't work because field #3 is separated with space
> but field #2 with '-'.
>
> %08lx-%08lx kind of sucks: 32-bit get aligned data so parsing can be
> faster by pointing to &p[8+1] but not on 64-bit.
> If scanf("%lx-%lx") is used then leading zeroes are useless.

This was similar to how '/proc/*/maps' file presents the  address range.
However, we could separate start and end address of the range with a
space, if that would be preferred.

> Text is harder than it looks.

We could make each line fixed length.  It could be  "%016lx %016lx %04d"
i.e 4 digit for node number?

> Please in the name of everything holy add new honest system call.