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Message-ID: <47D8A63D.3050903@FreeBSD.org>
Date: Thu, 13 Mar 2008 03:57:49 +0000
From: "Bruce M. Simpson" <bms@FreeBSD.org>
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To: Robert Watson <rwatson@FreeBSD.org>
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Cc: net@FreeBSD.org
Subject: Re: FYI: inpcb/pcbinfo mutex -> rwlock at some point in the
 mid-distant future
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Robert Watson wrote:
> One of those issues is that we need to demonstrate to ourselves that 
> exclusive access contention is managed as well with rwlocks as with 
> sleep mutexes, as these locks would continue to be fairly highly 
> contended in TCP.  The other issue is that rwlocks don't support full 
> priority propagation for reader access, although Jeff Roberson has 
> recently improved fairness to writers with many readers.

Don't forget that p4 bms_netdev contains a number of optimizations for 
the multicast paths -- there are lock acquisitions which are quite often 
unnecessary, or whose granularity is too high for the data structure(s) 
which need to be shared.

BMS