Date: Mon, 26 Nov 2007 09:13:51 -0800 From: Sam Leffler <sam@errno.com> To: Robert Watson <rwatson@freebsd.org> Cc: Perforce Change Reviews <perforce@freebsd.org>, Kip Macy <kmacy@freebsd.org> Subject: Re: PERFORCE change 129544 for review Message-ID: <474AFECF.4010402@errno.com> In-Reply-To: <20071126115044.J65286@fledge.watson.org> References: <200711260527.lAQ5RNSw090238@repoman.freebsd.org> <20071126115044.J65286@fledge.watson.org>
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Robert Watson wrote: > > On Mon, 26 Nov 2007, Kip Macy wrote: > >> http://perforce.freebsd.org/chv.cgi?CH=129544 >> >> Change 129544 by kmacy@kmacy:storage:toestack on 2007/11/26 05:26:43 >> >> disable merging of data into existing mbufs if >> new SB_TOE flag is set > > One of the reasons we compact socket buffers with TCP and other stream > protocols is that if you're dealing with an application/protocol that > spits out data in small chunks (i.e., a series of printfs) and nagel > is disabled, you end up with a series of packets that make quite > inefficient use of mbufs, as the space wasted per chunk of data is > significant. Not only that, we bill for space in socket buffers based > on the space held by the full mbuf, not just the data in the mbuf when > it comes to socket buffer resource limits, so you can rapidly fill up > socket buffer limits without compaction in this type of scenario. I'm > not sure which protocols this would affect, but I'd imagine that > RPC-like protocols supporting asynchronous operation (so that you get > a series of replies and responses in flight at once) might be > relevant, such as IMAP. > > On an unrelated not, if we want a non-coalescing modes for socket > bufferss, we should probably also give it a name like "SB_NOCOALESCE" > rather than something TOE-specific. There used to be a record boundary indication to inhibit coalescing. Sam
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