netdev - Re: [PATCH v2 net-next 0/12] bpf: map pre-alloc

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Date:	Tue, 8 Mar 2016 10:13:12 +0100
From:	Daniel Wagner <daniel.wagner@...-carit.de>
To:	Alexei Starovoitov <ast@...com>,
	"David S . Miller" <davem@...emloft.net>
CC:	Daniel Borkmann <daniel@...earbox.net>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	Wang Nan <wangnan0@...wei.com>, He Kuang <hekuang@...wei.com>,
	Martin KaFai Lau <kafai@...com>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel-team@...com>
Subject: Re: [PATCH v2 net-next 0/12] bpf: map pre-alloc

Hi Alexei,

On 03/08/2016 06:57 AM, Alexei Starovoitov wrote:
> v1->v2:
> . fix few issues spotted by Daniel
> . converted stackmap into pre-allocation as well
> . added a workaround for lockdep false positive
> . added pcpu_freelist_populate to be used by hashmap and stackmap
> 
> this path set switches bpf hash map to use pre-allocation by default
> and introduces BPF_F_NO_PREALLOC flag to keep old behavior for cases
> where full map pre-allocation is too memory expensive.
> 
> Some time back Daniel Wagner reported crashes when bpf hash map is
> used to compute time intervals between preempt_disable->preempt_enable
> and recently Tom Zanussi reported a dead lock in iovisor/bcc/funccount
> tool if it's used to count the number of invocations of kernel
> '*spin*' functions. Both problems are due to the recursive use of
> slub and can only be solved by pre-allocating all map elements.

I gave it a short spin and lathist sample works just fine.

cheers,
daniel