netdev - Re: [net-next.git 3/8 (V2)] stmmac: add the initial tx coalesce schema

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Date:	Thu, 13 Sep 2012 16:23:33 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	peppe.cavallaro@...com
Cc:	netdev@...r.kernel.org, bhutchings@...arflare.com
Subject: Re: [net-next.git 3/8 (V2)] stmmac: add the initial tx coalesce
 schema

From: Giuseppe CAVALLARO <peppe.cavallaro@...com>
Date: Tue, 11 Sep 2012 08:55:09 +0200

> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&priv->tx_lock, flags);
>  
> -	spin_lock(&priv->tx_lock);
> +	priv->xstats.tx_clean++;

You are changing the locking here for the sake of the new timer.

But timers run in software interrupt context, so this change is
completely unnecessary since NAPI runs in software interrupt context
as well, and neither timers nor NAPI run in hardware interrupts
context.

Therefore, disabling hardware interrupts for this lock is unnecessary
and will decrease performance.
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