linux-kernel - Re: [PATCH 13/17] net: stmmac: Implement NAPI for TX

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Message-Id: <20170131.231225.59679013563845652.davem@davemloft.net>
Date:   Tue, 31 Jan 2017 23:12:25 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     clabbe.montjoie@...il.com
Cc:     peppe.cavallaro@...com, alexandre.torgue@...com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/17] net: stmmac: Implement NAPI for TX

From: Corentin Labbe <clabbe.montjoie@...il.com>
Date: Tue, 31 Jan 2017 10:11:48 +0100

> The stmmac driver run TX completion under NAPI but without checking
> the work done by the TX completion function.

The current behavior is correct and completely intentional.

A driver should _never_ account TX work to the NAPI poll budget.

This is because TX liberation is orders of magnitude cheaper than
receiving a packet, and such SKB freeing makes more SKBs available
for RX processing.

Therefore, TX work should never count against the NAPI budget.

Please do not fix something which is not broken.