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Message-ID: <3DF5075A.2090009@colorfullife.com>
Date: Mon, 09 Dec 2002 22:12:58 +0100
From: Manfred Spraul <manfred@colorfullife.com>
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To: "David S. Miller" <davem@redhat.com>
CC: wli@holomorphy.com, anton@samba.org, linux-kernel@vger.kernel.org
Subject: Re: 2.5.50-BK + 24 CPUs
References: <20021208212808.GY9882@holomorphy.com>	<1039389778.13079.1.camel@rth.ninka.net>	<3DF4CCCE.7040407@colorfullife.com> <20021209.121557.17268348.davem@redhat.com>
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David S. Miller wrote:

>   From: Manfred Spraul <manfred@colorfullife.com>
>   Date: Mon, 09 Dec 2002 18:03:10 +0100
>
>   Unfortunately zero-copy doesn't help to avoid the schedules:
>   Zero copy just avoid the copy to kernel - you still need one schedule 
>   for each page to be transfered.
>
>The zerocopy patches copied up to 64k (or rather, 16 pages, something
>like that) at once, that's going to lead to 16 times less schedules.
>
>The 64k number was decided arbitrarily (it's what freebsd's pipe code
>uses) and it can be experimented with.
>  
>
Only if user space writes in 64 kB chunks - if user space writes 4 kB 
chunks, then zerocopy doesn't help much against schedule [depending on 
the implementation, it halves the number of schedules].
And page table tricks (COW) tricks are not acceptable.

--
    Manfred

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