Date: Sat, 14 Mar 1998 11:53:18 -0700 (MST) From: Kenneth Merry <ken@plutotech.com> To: karl@mcs.net (Karl Denninger) Cc: scsi@FreeBSD.ORG Subject: Re: CAM question Message-ID: <199803141853.LAA21278@pluto.plutotech.com> In-Reply-To: <19980314122132.45239@mcs.net> from Karl Denninger at "Mar 14, 98 12:21:32 pm"
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Karl Denninger wrote... > > I put CAM into a -CURRENT kernel last night. > > I like the layer, it seems to have significantly helped performance and > general operation of the system. > > HOWEVER, it immediately broke "systat", even after a rebuild. It now > complains that "dk_ndrive = 0" in the kernel and refuses to allow a "vmstat" > display. > > Since "iostat" works after the rebuild, obviously the stats are THERE. > What's missing? The answer is time. In CAM, there is a completely new kernel statistics interface. Look in sys/sys/devicestat.h and sys/kern/subr_devstat.c. The old interface only allowed you to gather dk_ndrive drives worth of statistics. The new devstat interface allows you to gather statistics on every I/O device in the system. It also keeps more statistics than the old stat system, and many of the counters are 64 bits, so they won't wrap very frequently on high-I/O systems. The devstat information is available through sysctl, so you don't have to go groking through /dev/mem to get it. The CAM layer does not use the old interface at all, so it isn't possible to get statistics that way. As a proof of concept, and to just have something that worked, I rewrote iostat back in November/December. systat is on my list of things to do, but that list keeps getting longer. (thankfully, most of the pieces of the list are CAM-related in one way or another) In any case, if someone wants to try their hand at porting systat, I'll be more than happy to help. Some of the code in iostat, albeit a little complicated, might be helpful in porting systat. Ken -- Kenneth Merry ken@plutotech.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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