netdev - Re: setsockopt()

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Message-ID: <20080708235125.GA11699@citi.umich.edu>
Date:	Tue, 8 Jul 2008 19:51:26 -0400
From:	Jim Rees <rees@...ch.edu>
To:	John Heffner <johnwheffner@...il.com>
Cc:	netdev@...r.kernel.org, aglo@...i.umich.edu, shemminger@...tta.com,
	bfields@...ldses.org
Subject: Re: setsockopt()

John Heffner wrote:

  I actually like your idea for a "soft"
  SO_SNDBUF -- ask the kernel for at least that much, but let it
  autotune higher if needed.  This is almost trivial to implement --
  it's the same as SO_SNDBUF but don't set the sock sndbuf lock.

Which brings me to another issue.  The nfs server doesn't call
sock_setsockopt(), it diddles sk_sndbuf and sk_rcvbuf directly, so as to get
around the max socket buf limit.  I don't like this.  If this is a legit
thing to do, there should be an api.

I'm thinking we need a sock_set_min_bufsize(), where the values passed in
are minimums, subject to autotuning, and maybe are not limited by the max.
It would, as you say, just set sk_sndbuf and sk_rcvbuf without setting the
corresponding flags SOCK_SNDBUF_LOCK and SOCK_RCVBUF_LOCK.

Would this do the trick, or is there a danger that autotuning would reduce
the buffer sizes below the given minimum?  If so, we might need
sk_min_rcvbuf or something like that.
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