Re: [PATCH 2.6.13] IOCHK interface for I/O error handling/detecting (for ia64)

From: david mosberger <>
Date: 2005-09-03 04:16:10
On 9/2/05, Grant Grundler <> 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

Reads are slow, sure, but writes are not (or should not).

Mosberger Consulting LLC, voice/fax: 510-744-9372,
35706 Runckel Lane, Fremont, CA 94536
To unsubscribe from this list: send the line "unsubscribe linux-ia64" in
the body of a message to
More majordomo info at
Received on Sat Sep 03 04:16:54 2005

This archive was generated by hypermail 2.1.8 : 2005-09-03 04:17:00 EST