netdev - Re: OOM when adding ipv6 route: How to make available more per-cpu memory?

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Date:	Fri, 05 Nov 2010 23:11:43 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	NetDev <netdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: OOM when adding ipv6 route:  How to make available more
 per-cpu memory?

Le vendredi 05 novembre 2010 à 21:20 +0100, Eric Dumazet a écrit :
> Your vmalloc space is very fragmented. pcpu_get_vm_areas() want
> hugepages (4MB on your machine, 2MB on mine because I have
> CONFIG_HIGHMEM64G=y)

Well, this is wrong. We use normal (4KB) pages, unfortunately.

I have a NUMA machine, with two nodes, so pcpu_get_vm_areas() allocates
two zones, one for each node, with a 'known' offset between them.
Then, 4KB pages are allocated to populate the zone when needed.

# grep pcpu_get_vm_areas /proc/vmallocinfo 
0xffffe8ffa0400000-0xffffe8ffa0600000 2097152 pcpu_get_vm_areas+0x0/0x740 vmalloc
0xffffe8ffffc00000-0xffffe8ffffe00000 2097152 pcpu_get_vm_areas+0x0/0x740 vmalloc

BTW, we dont have the number of pages currently allocated in each
'vmalloc' zone, and/or node information.

Tejun, do you have plans to use hugepages eventually ?
(and fallback to 4KB pages, but most percpu data are allocated right
after boot)

Thanks

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