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Date:      Sun, 11 Mar 2007 00:57:55 -0500
From:      "Keith Arner" <vornum@gmail.com>
To:        "Robert Watson" <rwatson@freebsd.org>
Cc:        Dave Baukus <david.baukus@us.fujitsu.com>, net@freebsd.org
Subject:   Re: netisr_direct
Message-ID:  <8e552a500703102157p1845926au65bb3adaf81c01c0@mail.gmail.com>
In-Reply-To: <20070310035135.B30274@fledge.watson.org>
References:  <45C0CA5D.5090903@incunabulum.net> <45E6BEE0.2050307@FreeBSD.org> <45E6C22D.7060200@freebsd.org> <45E6D70C.10104@FreeBSD.org> <45EEB086.3050409@FreeBSD.org> <45F03269.7050705@FreeBSD.org> <45F08F1D.5080708@us.fujitsu.com> <20070310035135.B30274@fledge.watson.org>

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On 3/9/07, Robert Watson <rwatson@freebsd.org> wrote:

>   It also introduces
> parallelism in the in-bound network layer processing path by allowing
> processing to occur in more than one thread at a time.  However, you can
> see


>From the experimentation I've done, it seems that for TCP loads at least,
the
input path tends to bottleneck on INP_INFO_WLOCK(&tcbinfo), essentially
reducing the input path to a single thread.

reduced parallelism in some environments as the ithread no longer run
> concurrently with the netisr.  I would not use net.isr.direct in versions
> of
> FreeBSD before 6.1, but it should be pretty safe for 6.1 and later.
>

Admitedly, the experimentation I've done has been with 6.0, rather than 6.1.
Have there been any changes in 6.1 that address the locking in the TCP input
path?  I'm very interested in being able to run highly parallel TCP loads.

Keith



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