linux-kernel - Re: [PATCH RFC 2/2] net: Optimize snmp stat aggregation by walking all the percpu data at once

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Message-ID: <1440518424.8932.19.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 25 Aug 2015 09:00:24 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
Cc:	davem@...emloft.net, kuznet@....inr.ac.ru, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org, kaber@...sh.net, jiri@...nulli.us,
	edumazet@...gle.com, hannes@...essinduktion.org,
	tom@...bertland.com, azhou@...ira.com, ebiederm@...ssion.com,
	ipm@...rality.org.uk, nicolas.dichtel@...nd.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	anton@....ibm.com, nacc@...ux.vnet.ibm.com,
	srikar@...ux.vnet.ibm.com
Subject: Re: [PATCH RFC 2/2] net: Optimize snmp stat aggregation by walking
 all the percpu data at once

On Tue, 2015-08-25 at 21:17 +0530, Raghavendra K T wrote:
> On 08/25/2015 07:58 PM, Eric Dumazet wrote:

> >
> >
> > This is a great idea, but kcalloc()/kmalloc() can fail and you'll crash
> > the whole kernel at this point.
> >
> 
> Good catch, and my bad. Though system is in bad memory condition,
> since fill_stat is not critical for the system do you think silently
> returning from here is a good idea?
> or do you think we should handle with -ENOMEM way up.?

Hmm... presumably these 288 bytes could be allocated in
inet6_fill_ifla6_attrs() stack frame.

Also it is weird we fill all these stats for a device we just created
and never enabled : initial stats are all 0 for them.


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