Date: Wed, 22 Mar 2006 13:12:34 -0500 From: Mikhail Teterin <mi+mx@aldan.algebra.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Kostik Belousov <kostikbel@gmail.com>, alc@freebsd.org, stable@freebsd.org Subject: Re: more weird bugs with mmap-ing via NFS Message-ID: <200603221312.38502.mi%2Bmx@aldan.algebra.com> In-Reply-To: <200603221723.k2MHNmu0012943@apollo.backplane.com> References: <200603211607.30372.mi%2Bmx@aldan.algebra.com> <20060322091010.GA20929@deviant.kiev.zoral.com.ua> <200603221723.k2MHNmu0012943@apollo.backplane.com>
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ÓÅÒÅÄÁ 22 ÂÅÒÅÚÅÎØ 2006 12:23, Matthew Dillon ÷É ÎÁÐÉÓÁÌÉ: > My guess is that you are exporting the filesystem as a particular > user id that is not root (i.e. you do not have -maproot=root: in the > exports line on the server). Yes, indeed, re-exporting with -maproot=0 leads to normal behavior. Thanks for the workaround! Here are the stats: As the program is working hard, the incoming traffic on the client is about 200Kb/s (I guess, all those not yet existant pages being faulted in) and the outgoing -- about 7Kb/s with occasional spikes to 8Mb/s (I guess, this is when the flushing takes place). > š š What is likely happening is that the NFS client is trying to push out > š š the pages using the root uid rather then the user uid. šThis is a > highly probable circumstance for VM pages because once they get > disassociated from the related buffer cache buffer, the cred information > for the last process to modify the related VM pages is lost. šWhen the > kernel tries to flush the pages out it winds up using root creds. So mmap is just a more "reliable" way to trigger this problem, right? Is not this, like, a major bug? A file can be opened, written to for a while, and then -- at a semi-random moment -- the log will drop across the road? Ouch... Thanks a lot to all concerned for helping solve this problem. Yours, -mi
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