netdev - RE: [PATCH net-next 2/2] net/mlx4: Revert "mlx4: set maximal number of default RSS queues"

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Date:	Wed, 1 Jan 2014 18:46:42 +0000
From:	Yuval Mintz <yuvalmin@...adcom.com>
To:	Amir Vadai <amirv@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eugenia Emantayev <eugenia@...lanox.com>,
	Ido Shamay <idos@...lanox.com>
Subject: RE: [PATCH net-next 2/2] net/mlx4: Revert "mlx4: set maximal number
 of default RSS queues"

> From: Eugenia Emantayev <eugenia@...lanox.com>
> 
> This reverts commit 90b1ebe "mlx4: set maximal number of default RSS
> queues".
> Limiting the number of receive rings to default (8) reduces overall
> packet rate by 15% in multiple TCP streams application:
> 
>           Packet rate
> 8  rings  967691
> 16 rings  1142070
> 
> Results were obtained using netperf:
> 
> S=200 ; ( for i in $(seq 1 $S) ; do ( \
>   netperf -H 11.7.13.55 -t TCP_RR -l 30 &) ; \
>   wait ; done | grep "1        1" | awk '{SUM+=$6} END {print SUM}' )

Seems odd - well, to be more exact, nothing is odd about the results;
the whole notion of the original patch was to set an upper limit on the
number of  interrupt vectors multi-queue devices ask by default, not
to improve the default performance.

If you believe this is a better default (or some relaxation will be, 
e.g.,  16 instead of 8),  why not set it as default for ALL multi-queue 
networking drivers?

Thanks,
Yuval
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