Date: Sun, 9 Aug 2009 20:16:28 +0200 From: Attilio Rao <attilio@freebsd.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: freebsd-usb@freebsd.org Subject: Re: Performance issues Message-ID: <3bbf2fe10908091116x3ac66e63t4b34174f492a4bce@mail.gmail.com> In-Reply-To: <20090809.115606.1943337744.imp@bsdimp.com> References: <20090809.105507.-646227496.imp@bsdimp.com> <3bbf2fe10908091025t7f8d00dbw5b0589728cf400ad@mail.gmail.com> <3bbf2fe10908091038m3efb3612l2923d8b3238e111f@mail.gmail.com> <20090809.115606.1943337744.imp@bsdimp.com>
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2009/8/9 M. Warner Losh <imp@bsdimp.com>: > In message: <3bbf2fe10908091038m3efb3612l2923d8b3238e111f@mail.gmail.com> > Attilio Rao <attilio@freebsd.org> writes: > : 2009/8/9 Attilio Rao <attilio@freebsd.org>: > : > 2009/8/9 M. Warner Losh <imp@bsdimp.com>: > : >> In message: <200908091840.55000.hselasky@c2i.net> > : >> Hans Petter Selasky <hselasky@c2i.net> writes: > : >> : On Sunday 09 August 2009 18:23:41 M. Warner Losh wrote: > : >> : > Any ideas how to track this down? > : >> : > : >> : Hi, > : >> : > : >> : USB is only draining from "usbd_transfer_drain()" in > : >> : /sys/dev/usb/usb_transfer.c . You could add a print including the backtrace > : >> : and see if that function gets called when it freezes. > : >> > : >> Ummm. No. Adding a traceback print to a function that's called 60 > : >> times a second in steady state doesn't seem like a viable option. > : >> > : >> : Else I would try to compile a fresh kernel from USB P4. There are > : >> : some patches there in relation to the recent newbus lock change, > : >> : that might help. > : >> > : >> This kernel predates the newbus lock change. > : >> > : >> : USB uses uppercase "WDRAIN". Is your printout lowercase "wdrain" ? > : >> > : >> Yes. > : > > : > That's used by the buffer cache in order to reduce pressure of > : > asynchronous writes. It waits for other writes to complete before to > : > go on. Probabilly, I/O requests get stuck for another reasong starving > : > the asynchronous requests queue flushing. > : > : It would be also interesting to understand if the allowed requests are > : just lost or still pending and can be effectively flushed out. Can you > : please show the content of vm.runningbufspace ? > > The writes eventually happen, it is just stalled. I'll run the > experiment again and see if I can give you that info... > > : However, keep in mind that as long as the buffer cache is global, if > : the bluethoot dongle breaks I/O requests, it can be the offending > : part, so USB may not be involved. > > I'm not sure I understand this statement. I think what is happening > is a race between multiple devices. I also see problems when I have > both a usb disk and a usb dvd burner attached. I didn't used to see > that problem (I made hundreds of DVDs of my son's hockey games). Now, > I can't even burn one disc to save my life... > > Besides, the bluetooth dongle isn't going to be doing any disk block > requests, so how can that interfere with the buffer cache? Ok, so it should not. Can you compile a KTR kernel with KTR_BUF and monitor the buffer cache activity? Please just stop it collecting points early otherwise we could loose many interesting informations due to KTR buffer entries replacements politique. Attilio -- Peace can only be achieved by understanding - A. Einstein
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