Date: Fri, 23 Jul 2010 08:47:12 +0300 From: Alexander Motin <mav@FreeBSD.org> To: Jerry Toung <jrytoung@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: Giant free GEOM/CAM XPT Message-ID: <4C492CE0.3050105@FreeBSD.org> In-Reply-To: <mailpost.1279833356.3711031.57007.mailing.freebsd.hackers@FreeBSD.cs.nctu.edu.tw> References: <mailpost.1279833356.3711031.57007.mailing.freebsd.hackers@FreeBSD.cs.nctu.edu.tw>
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Jerry Toung wrote: > Hello List, > while going through the xpt code (8.0 RELEASE), it seems to me that some > gains can be had > in src/sys/geom/geom_disk.c where dp->d_strategy(bp2) is surrounded by Giant > lock. Especially in the case > where one has 2+ controllers on the system with /dev/daXX attached to them > during heavy I/O. Giant locked there only if DISKFLAG_NEEDSGIANT flag is set, which da driver is not doing. > I am currently trying to get rid of giant there, but it branches in sys/cam > and sys/dev/twa. Definitely not a > trivial exercise. The dependency on Giant seems to come from the XPT code. > > would be neat if I could just use the SIM lock, which is per controller. > > Question: do you think it's worth the effort? I think you misunderstood something. Most of CAM protected by SIM locks. If some SIMs use Giant for that purpose - it is their own problem. But as I can see, twa uses own lock, not Giant. -- Alexander Motin
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