Messages in this thread | | | Date | Fri, 2 Sep 2005 09:48:28 -0700 | From | Grant Grundler <> | Subject | Re: [PATCH 2.6.13] IOCHK interface for I/O error handling/detecting (for ia64) |
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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".
> 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/
Then we can talk about the cost of spinlocks vs cost of MMIO access.
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