On 9/2/05, Grant Grundler <[EMAIL PROTECTED]> wrote: > On Thu, Sep 01, 2005 at 05:45:54PM -0500, Brent Casavant wrote: > ... > > The first is serialization of all I/O reads and writes. This will > > be a severe problem on systems with large numbers of PCI buses, the > > very type of system that stands the most to gain in reliability from > > these efforts. At a minimum any locking should be done on a per-bus > > basis. > > The lock could be per "error domain" - that would require some > arch specific support though to define the scope of the "error domain".
I do not think the basic inX/outX and readX/writeX operations should involve spinlocks. That would be really nasty if an MCA/INIT handler had to call them, for example... > > The second is the raw performance penalty from acquiring and dropping > > a lock with every read and write. This will be a substantial amount > > of activity for any I/O-intensive system, heck even for moderate I/O > > levels. > > Sorry - I think this is BS. > > Please run mmio_test on your box and share the results. > mmio_test is available here: > svn co http://svn.gnumonks.org/trunk/mmio_test/ Reads are slow, sure, but writes are not (or should not). --david -- Mosberger Consulting LLC, voice/fax: 510-744-9372, http://www.mosberger-consulting.com/ 35706 Runckel Lane, Fremont, CA 94536 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
