netdev - Re: [PATCH net-next,v5] net/tls: Calculate nsg for zerocopy path without skb_cow

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Message-Id: <20180829.195722.531666131078420785.davem@davemloft.net>
Date:   Wed, 29 Aug 2018 19:57:22 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     doronrk@...com
Cc:     aviadye@...lanox.com, vakul.garg@....com, davejwatson@...com,
        borisp@...lanox.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next,v5] net/tls: Calculate nsg for zerocopy path
 without skb_cow_data.

From: Doron Roberts-Kedes <doronrk@...com>
Date: Tue, 28 Aug 2018 16:33:57 -0700

> decrypt_skb fails if the number of sg elements required to map it
> is greater than MAX_SKB_FRAGS. nsg must always be calculated, but
> skb_cow_data adds unnecessary memcpy's for the zerocopy case.
> 
> The new function skb_nsg calculates the number of scatterlist elements
> required to map the skb without the extra overhead of skb_cow_data.
> This patch reduces memcpy by 50% on my encrypted NBD benchmarks.
> 
> Reported-by: Vakul Garg <Vakul.garg@....com>
> Reviewed-by: Vakul Garg <Vakul.garg@....com>
> Tested-by: Vakul Garg <Vakul.garg@....com>
> Signed-off-by: Doron Roberts-Kedes <doronrk@...com>

Applied, thank you.