netdev - RE: [PATCH net-next V3 05/16] net: fec: reduce interrupts

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Date:	Wed, 6 Apr 2016 10:06:25 +0000
From:	Fugang Duan <fugang.duan@....com>
To:	Troy Kisky <troy.kisky@...ndarydevices.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"lznuaa@...il.com" <lznuaa@...il.com>
CC:	Fabio Estevam <fabio.estevam@....com>,
	"l.stach@...gutronix.de" <l.stach@...gutronix.de>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"tremyfr@...il.com" <tremyfr@...il.com>,
	"gerg@...inux.org" <gerg@...inux.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"johannes@...solutions.net" <johannes@...solutions.net>,
	"stillcompiling@...il.com" <stillcompiling@...il.com>,
	"sergei.shtylyov@...entembedded.com" 
	<sergei.shtylyov@...entembedded.com>,
	"arnd@...db.de" <arnd@...db.de>
Subject: RE: [PATCH net-next V3 05/16] net: fec: reduce interrupts

From: Troy Kisky <troy.kisky@...ndarydevices.com> Sent: Wednesday, April 06, 2016 10:26 AM
> To: netdev@...r.kernel.org; davem@...emloft.net; Fugang Duan
> <fugang.duan@....com>; lznuaa@...il.com
> Cc: Fabio Estevam <fabio.estevam@....com>; l.stach@...gutronix.de;
> andrew@...n.ch; tremyfr@...il.com; gerg@...inux.org; linux-arm-
> kernel@...ts.infradead.org; johannes@...solutions.net;
> stillcompiling@...il.com; sergei.shtylyov@...entembedded.com;
> arnd@...db.de; Troy Kisky <troy.kisky@...ndarydevices.com>
> Subject: [PATCH net-next V3 05/16] net: fec: reduce interrupts
> 
> By clearing the NAPI interrupts in the NAPI routine and not in the interrupt
> handler, we can reduce the number of interrupts. We also don't need any status
> variables as the registers are still valid.
> 
> Also, notice that if budget pkts are received, the next call to fec_enet_rx_napi
> will now continue to receive the previously pending packets.
> 
> To test that this actually reduces interrupts, try this command before/after patch
> 
> cat /proc/interrupts |grep ether; \
> ping -s2800 192.168.0.201 -f -c1000 ; \
> cat /proc/interrupts |grep ether
> 
> For me, before this patch is 2996 interrupts.
> After patch is 2010 interrupts.
> 
> Signed-off-by: Troy Kisky <troy.kisky@...ndarydevices.com>
>

As my previous comments on V2, if you want to improve performance, you can try to separate tx and rx napi process like calling netif_tx_napi_add() to initialize tx NAPI context.