netdev - Re: [PATCH net-next] net: bcmgenet: collect Rx discarded packet count

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Message-Id: <20150310.172905.949955668286642370.davem@davemloft.net>
Date:	Tue, 10 Mar 2015 17:29:05 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	pgynther@...gle.com
Cc:	f.fainelli@...il.com, netdev@...r.kernel.org, jaedon.shin@...il.com
Subject: Re: [PATCH net-next] net: bcmgenet: collect Rx discarded packet
 count

From: Petri Gynther <pgynther@...gle.com>
Date: Tue, 10 Mar 2015 13:52:32 -0700

> It is a rare event that discards > 0. Thus, the extra register write
> happens very infrequently.
> 
> And, writing 0 to RDMA_PROD_INDEX does not reset the producer index
> bits 15:0 that are used in Rx processing.

You can defer the write until you see the 0xffff saturation value.

Or, perhaps, half the saturation value.

Anything is better than doing it on any discard, because this overhead
will make whatever is causing the cpu to be backlogged even worse.
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