Date: Wed, 13 Mar 2013 19:18:43 +0400 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Andre Oppermann <andre@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r248196 - head/sys/nfs Message-ID: <20130313151843.GS48089@FreeBSD.org> In-Reply-To: <513F9BC9.3060300@freebsd.org> References: <201303121219.r2CCJN5Z069789@svn.freebsd.org> <513F3A54.3090702@freebsd.org> <20130312150053.GI48089@FreeBSD.org> <513F4A39.8040107@freebsd.org> <20130312155005.GJ48089@FreeBSD.org> <513F58C0.4050302@freebsd.org> <20130312194936.GL48089@FreeBSD.org> <513F9BC9.3060300@freebsd.org>
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Okay, I will redo my patch to make default not to allow > PAGE_SIZE clusters. On Tue, Mar 12, 2013 at 10:19:05PM +0100, Andre Oppermann wrote: A> Jumbos always were physically contiguous. That was the very reason for A> their existence. They were invented to allow early NIC's with limited A> DMA capabilities to handle jumbo ethernet frames. Today they should only A> be used for DMA challenged NIC's and nothing else. They definitely were not physically contigous prior to r174247. A> > Let me repeat: there is a lot of code, that does handmade allocation of A> > an mbuf chain of an arbitrary length using mbufs and common clusters. This A> > code can be cut and use m_getm2(), if we can restrict it to avoid page size A> > clusters. I don't have time to dig deeper in the code and analyze and test A> > whether it can support page sized clusters in chains. A> A> m_getm2() can be used in any such case and doesn't have to avoid PAGE_SIZE A> clusters. PAGE_SIZE jumbo clusters are fine. Larger than PAGE_SIZE is not. A> A> When the code is able to work with mbuf chains the exact size of each cluster A> isn't important anymore. We can use the optimal size. Do you volunteer to fix if anything is broken? If not, I'd prefer to be conservative and make m_getm() capable to produce chains without clusters bigger than MCLBYTES. -- Totus tuus, Glebius.
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