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Message-Id: <20150202.181834.2201965486446161539.davem@davemloft.net> Date: Mon, 02 Feb 2015 18:18:34 -0800 (PST) From: David Miller <davem@...emloft.net> To: eric.dumazet@...il.com Cc: netdev@...r.kernel.org Subject: Re: [PATCH net-next] pkt_sched: fq: better control of DDOS traffic From: Eric Dumazet <eric.dumazet@...il.com> Date: Fri, 30 Jan 2015 06:06:12 -0800 > From: Eric Dumazet <edumazet@...gle.com> > > FQ has a fast path for skb attached to a socket, as it does not > have to compute a flow hash. But for other packets, FQ being non > stochastic means that hosts exposed to random Internet traffic > can allocate million of flows structure (104 bytes each) pretty > easily. Not only host can OOM, but lookup in RB trees can take > too much cpu and memory resources. > > This patch adds a new attribute, orphan_mask, that is adding > possibility of having a stochastic hash for orphaned skb. > > Its default value is 1024 slots. > > This patch also handles the specific case of SYNACK messages: > > They are attached to the listener socket, and therefore all map > to a single hash bucket. If listener have set SO_MAX_PACING_RATE, > hoping to have new accepted socket inherit this rate, SYNACK > might be paced and even dropped. > > This is very similar to an internal patch Google have used more > than one year. > > Signed-off-by: Eric Dumazet <edumazet@...gle.com> Can you document the mask value a little bit more? For example, I don't understand why "(1024 - 1) << 1" means 1024 slots just from looking at this change. Thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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