Date: Mon, 29 Sep 1997 12:01:24 +0100 From: Alan Judge <Alan.Judge@indigo.ie> To: scsi@freebsd.org, stable@freebsd.org Subject: Kernel disk hangs under load with 2.2-STABLE Message-ID: <199709291101.MAA16750@indigo.ie>
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[Posting to both scsi and stable, since I'm not sure which is at fault and if there is a hang bug in 2.2-STABLE, it would be good to find it.] I have a machine running squid (with the data stored on a CCD striped set of disks). Since it's a major web cache, the disks get a fairly steady and sometimes heavy load. The machine doesn't do anything else and squid is the only large process (RSS of 120MB on a 256MB machine). The kernel is 2.2-STABLE, cvsuped last Tuesday; hardware is dual Adaptec 2940UWs with Quantum Atlas II UW disks. No unusual config options other than increases of NBUF and NMBCLUSTERS. Every so often (about once in two to three days), the squid process hangs and shows up in D state in ps. The process cannot be killed and commands that are disk related sometimes hang. The only cure is to reboot, and the reboot is usually not clean (syncing disks, .... giving up). Oddly, reducing the size of the web cache (which indirectly reduces squids RSS and the proportion of the CCD array in use) reduces the frequency of the hangs. I know that's probably not enough info to find a bug. Any suggestions on how to start debugging this? What commands should I try? How do I find what squid is stuck waiting for? Should I bring up gdb or DDB and look at something? -- Alan Judge Phone: +353-1-6046901 Indigo Network Operations Centre Fax: +353-1-6046948
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