From: "David S. Miller" <davem@redhat.com>
To: Russell King <rmk@arm.linux.org.uk>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Zerocopy implementation issues
Date: Sun, 29 Apr 2001 04:32:57 -0700 (PDT) [thread overview]
Message-ID: <15083.64489.305160.772564@pizda.ninka.net> (raw)
In-Reply-To: <20010429121841.F30243@flint.arm.linux.org.uk>
In-Reply-To: <20010429005206.J21792@flint.arm.linux.org.uk> <15083.40318.158099.137018@pizda.ninka.net> <20010429072342.B30041@flint.arm.linux.org.uk> <15083.52835.992666.897323@pizda.ninka.net> <20010429101739.D30243@flint.arm.linux.org.uk> <20010429113122.E30243@flint.arm.linux.org.uk> <15083.62888.860815.889046@pizda.ninka.net> <20010429121841.F30243@flint.arm.linux.org.uk>
Russell King writes:
> I'm doing it _NOW_, but I'm having to rotate the checksum
> at the end if dst & 1, only to have it unrotated in an
> inefficient manner in csum_block_*. Seems a bit of a
> waste of CPU cycles.
This is certainly the kind of enhancement we can make, where
possible. No problem.
But I currently can't see how you would apply it even
in the net/ipv4/tcp.c:tcp_copy_to_page() case. Look:
page_address(page) + off
This determines whether you need to rotate at the end
in your checksum code, right? We know pages are aligned
so 'off' is all that is relevant for that determination.
Later we use:
skb->len
to determine the behavior of csum_block_add() (to byte swap
or not).
There is no connection between 'off' and 'skb->len' so I
don't see how in this case we could make use of your optimization.
Later,
David S. Miller
davem@redhat.com
prev parent reply other threads:[~2001-04-29 11:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-04-28 23:52 Russell King
2001-04-29 4:50 ` David S. Miller
[not found] ` <20010429072342.B30041@flint.arm.linux.org.uk>
[not found] ` <15083.52835.992666.897323@pizda.ninka.net>
2001-04-29 8:39 ` Russell King
2001-04-29 9:17 ` Russell King
2001-04-29 10:31 ` Russell King
2001-04-29 11:06 ` David S. Miller
2001-04-29 11:18 ` Russell King
2001-04-29 11:32 ` David S. Miller [this message]
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