linux-kernel - Re: [PATCH v3 4/5] net: hpe: Add GXP UMAC Driver

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Message-ID: <88B3833C-19FB-4E4C-A398-E7EF3143ED02@hpe.com>
Date:   Fri, 18 Aug 2023 20:11:05 +0000
From:   "Hawkins, Nick" <nick.hawkins@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     "christophe.jaillet@...adoo.fr" <christophe.jaillet@...adoo.fr>,
        "simon.horman@...igine.com" <simon.horman@...igine.com>,
        "Verdun, Jean-Marie" <verdun@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 4/5] net: hpe: Add GXP UMAC Driver

Hi Andrew,

> > + length = 1514;
> > + }
> > +
> > + memset(pframe, 0, UMAC_MAX_FRAME_SIZE);
> > + memcpy(pframe, skb->data, length);


> Is this cached or uncached memory? uncached is expansive so you want
> to avoid touching it twice. Depending on how busy your cache is,
> touching it twice might cause it to expelled from L1 on the first
> write, so you could be writing to L2 twice for no reason. Do the math
> and calculate the tail space you need to zero.

> I would also suggest you look at the page pool code and use that for
> all you buffer handling. It is likely to be more efficient than what
> you have here.

Would this be the #include <linux/dmapool.h> library?

Thank you for the assistance,

-Nick Hawkins