netdev - Re: [PATCH net-next 03/10] tipc: sk_recv_queue size check only for connectionless sockets

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Message-ID: <20121207192030.GA30339@hmsreliant.think-freely.org>
Date:	Fri, 7 Dec 2012 14:20:30 -0500
From:	Neil Horman <nhorman@...driver.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Jon Maloy <jon.maloy@...csson.com>,
	Ying Xue <ying.xue@...driver.com>
Subject: Re: [PATCH net-next 03/10] tipc: sk_recv_queue size check only for
 connectionless sockets

On Fri, Dec 07, 2012 at 09:28:11AM -0500, Paul Gortmaker wrote:
> From: Ying Xue <ying.xue@...driver.com>
> 
> The sk_receive_queue limit control is currently performed for
> all arriving messages, disregarding socket and message type.
> But for connected sockets this check is redundant, since the protocol
> flow control already makes queue overflow impossible.
> 
Can you explain where that occurs?  I see where the tipc dispatch function calls
sk_add_backlog, which checks the per socket recieve queue (regardless of weather
the receiving socket is connection oriented or connectionless), but if the
receiver doesn't call receive very often, This just adds a check against your
global limit, doing nothing for your per-socket limits.  In fact it seems to
repeat the same check twice, as in the worst case of the incomming message being
TIPC_LOW_IMPORTANCE, its just going to check that the global limit is exactly
OVERLOAD_LIMIT_BASE/2 again.

Neil

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