Date: Fri, 12 Jul 2002 15:07:57 +0300 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: Bosko Milekic <bmilekic@unixdaemons.com> Cc: Luigi Rizzo <rizzo@icir.org>, freebsd-net@FreeBSD.org Subject: Re: mbuf external buffer reference counters Message-ID: <20020712120757.GE51735@hades.hell.gr> In-Reply-To: <20020711171255.A19014@unixdaemons.com> References: <20020711162026.A18717@unixdaemons.com> <20020711133802.A31827@iguana.icir.org> <20020711164225.A18852@unixdaemons.com> <20020711135608.A32460@iguana.icir.org> <20020711171255.A19014@unixdaemons.com>
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On 2002-07-11 17:12 +0000, Bosko Milekic wrote: > On Thu, Jul 11, 2002 at 01:56:08PM -0700, Luigi Rizzo wrote: > > example: userland does an 8KB write, in the old case this requires > > 4 clusters, with the new one you end up using 4 clusters and stuff > > the remaining 16 bytes in a regular mbuf, then depending on the > > relative producer-consumer speed the next write will try to fill > > the mbuf and attach a new cluster, and so on... and when TCP hits > > these data-in-mbuf blocks will have to copy rather than reference > > the data blocks... > > This is a good observation if we're going to be doing benchmarking, > but I'm not sure whether the repercussions are that important (unless, > as I said, there's a lot of applications that send exactly 8192 > byte chunks?). This is not true only for 8192 byte-sized writes. Anything that uses a block size >2048 near a power of 2 will have the same problem. Writes that use 2048 bytes, 4096, 8192, 16384, ... will all have this very same problem :/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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