Date: Mon, 9 Mar 2009 17:43:52 +0100 From: Nicolas Haller <nicolas@boiteameuh.org> To: freebsd-questions@freebsd.org Subject: Re: Busy disk and page fault Message-ID: <20090309164352.GE1481@boiteameuh.org> In-Reply-To: <alpine.BSF.2.00.0903091701500.2680@wojtek.tensor.gdynia.pl> References: <20090309153057.GD1481@boiteameuh.org> <alpine.BSF.2.00.0903091701500.2680@wojtek.tensor.gdynia.pl>
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On Mon, Mar 09, 2009 at 05:04:16PM +0100, Wojciech Puchar wrote: >> The server is overload, the disk is 100% busy with 250 write operations >> per second and a throuput of 6MB/s. >> My first idea is because of mass random access/write on the disk. But I also see >> the server can make 20k page fault per second. > what page fault? most page faults in FreeBSD doesn't mean disk access, > just no mapping present in page tables, which gets mapped after the > fault. > Only if page is actually not present in memory it is fetched from disk. > top shows in what state is a process. > if it's biord or biorw - it's doing disk/file I/O, not swapping. The box don't swap. I just ask if page fault interrupt postgresql process and fragment/de-optimize disk write. -- Nicolas Haller
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