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Message-ID: <20121207160733.GD29819@shamino.rdu.redhat.com> Date: Fri, 7 Dec 2012 11:07:33 -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 02/10] tipc: eliminate aggregate sk_receive_queue limit On Fri, Dec 07, 2012 at 09:28:10AM -0500, Paul Gortmaker wrote: > From: Ying Xue <ying.xue@...driver.com> > > As a complement to the per-socket sk_recv_queue limit, TIPC keeps a > global atomic counter for the sum of sk_recv_queue sizes across all > tipc sockets. When incremented, the counter is compared to an upper > threshold value, and if this is reached, the message is rejected > with error code TIPC_OVERLOAD. > > This check was originally meant to protect the node against > buffer exhaustion and general CPU overload. However, all experience > indicates that the feature not only is redundant on Linux, but even > harmful. Users run into the limit very often, causing disturbances > for their applications, while removing it seems to have no negative > effects at all. We have also seen that overall performance is > boosted significantly when this bottleneck is removed. > > Furthermore, we don't see any other network protocols maintaining > such a mechanism, something strengthening our conviction that this > control can be eliminated. > > Signed-off-by: Ying Xue <ying.xue@...driver.com> > Signed-off-by: Jon Maloy <jon.maloy@...csson.com> > Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com> > --- > net/tipc/socket.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/net/tipc/socket.c b/net/tipc/socket.c > index 1a720c8..a059ed0 100644 > --- a/net/tipc/socket.c > +++ b/net/tipc/socket.c > @@ -2,7 +2,7 @@ > * net/tipc/socket.c: TIPC socket API > * > * Copyright (c) 2001-2007, Ericsson AB > - * Copyright (c) 2004-2008, 2010-2011, Wind River Systems > + * Copyright (c) 2004-2008, 2010-2012, Wind River Systems > * All rights reserved. > * > * Redistribution and use in source and binary forms, with or without > @@ -1241,11 +1241,6 @@ static u32 filter_rcv(struct sock *sk, struct sk_buff *buf) > } > > /* Reject message if there isn't room to queue it */ > - recv_q_len = (u32)atomic_read(&tipc_queue_size); > - if (unlikely(recv_q_len >= OVERLOAD_LIMIT_BASE)) { > - if (rx_queue_full(msg, recv_q_len, OVERLOAD_LIMIT_BASE)) > - return TIPC_ERR_OVERLOAD; > - } If you're going to remove the one place that you read this variable, don't you also want to remove the points where you increment/decrement the atomic as well, and for that matter eliminate the definition itself? Neil -- 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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