linux-kernel - Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog

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Message-ID: <5670A577.3010207@iogearbox.net>
Date:	Wed, 16 Dec 2015 00:42:47 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Ming Lei <tom.leiming@...il.com>
CC:	linux-kernel@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 5/6] bpf: hash: avoid to call kmalloc() in eBPF prog

On 12/16/2015 12:10 AM, Alexei Starovoitov wrote:
...
> this rounding to cache line is great for performance, but it's extra
> memory upfront which may not be needed. The per-allocation is a classic
> performance vs memory trade-off. In other cases it may hurt.
> So could you change the patch to do pre-allocation only when
> requested by user space via extra flag for hash map or via
> new BPF_MAP_TYPE_HASH_PREALLOC type? Not sure yet whether flag or
> new type is better. I guess implementation will dictate.

Was also thinking about this, probably new map type makes sense.
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