Date: Sun, 10 Mar 2013 01:04:58 -0500 From: Garrett Wollman <wollman@bimajority.org> To: Jack Vogel <jfvogel@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: Limits on jumbo mbuf cluster allocation Message-ID: <20796.8842.691923.899276@hergotha.csail.mit.edu> In-Reply-To: <CAFOYbc=7iROKzUwnB0fMR=ix8VFo%2BONfG=NX43jeF7jkp74JhQ@mail.gmail.com> References: <20793.36593.774795.720959@hergotha.csail.mit.edu> <51399926.6020201@freebsd.org> <CAFOYbc=x7U-s70KvcZJdrVP6v-On716qMi=HN1P2Kj%2Bd_K972A@mail.gmail.com> <20794.6692.191898.682241@hergotha.csail.mit.edu> <513A2887.2010408@freebsd.org> <CAFOYbc=7iROKzUwnB0fMR=ix8VFo%2BONfG=NX43jeF7jkp74JhQ@mail.gmail.com>
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<<On Fri, 8 Mar 2013 12:13:28 -0800, Jack Vogel <jfvogel@gmail.com> said: > Yes, in the past the code was in this form, it should work fine Garrett, > just make sure > the 4K pool is large enough. [Andre Oppermann's patch:] >> if (adapter->max_frame_size <= 2048) adapter-> rx_mbuf_sz = MCLBYTES; >> - else if (adapter->max_frame_size <= 4096) >> + else adapter-> rx_mbuf_sz = MJUMPAGESIZE; >> - else if (adapter->max_frame_size <= 9216) >> - adapter->rx_mbuf_sz = MJUM9BYTES; >> - else >> - adapter->rx_mbuf_sz = MJUM16BYTES; So I tried exactly this, and it certainly worked insofar as only 4k clusters were allocated, but NFS performance went down precipitously (to fewer than 100 ops/s where normally it would be doing 2000 ops/s). I took a tcpdump while it was in this state, which I will try to make some sense of when I get back to the office. (It wasn't livelocked; in fact, the server was mostly idle, but responses would take seconds rather than milliseconds -- assuming the client could even successfully mount the server at all, which the Debian automounter frequently refused to do.) I ended up reverting back to the old kernel (which I managed to lose the sources for), and once I get my second server up, I will try to do some more testing to see if I can identify the source of the problem. -GAWollman
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