netdev - RE: [PATCH] net: ethernet: fs-enet: Use generic CRC32 implementation

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Message-ID: <5ef968e1cb2a473cad97f6bfead369ca@AcuMS.aculab.com>
Date:   Tue, 24 Jul 2018 11:05:59 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Krzysztof Kozlowski' <krzk@...nel.org>,
        Pantelis Antoniou <pantelis.antoniou@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Eric Biggers <ebiggers3@...il.com>
Subject: RE: [PATCH] net: ethernet: fs-enet: Use generic CRC32 implementation

From: Krzysztof Kozlowski
> Sent: 23 July 2018 17:20
> Use generic kernel CRC32 implementation because it:
> 1. Should be faster (uses lookup tables),

Are you sure?
The lookup tables are unlikely to be in the data cache and
the 6 cache misses kill performance.
(Not that it particularly matters when setting up multicast hash tables).

> 2. Removes duplicated CRC generation code,
> 3. Uses well-proven algorithm instead of coding it one more time.
...
> 
> Not tested on hardware.

Have you verified that the old and new functions give the
same result for a few mac addresses?
It is very easy to use the wrong bits in crc calculations
or generate the output in the wrong bit order.

	David

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