[PATCH 0/2] x86: Speed up ioremap operations
From: Mike Travis
Date: Fri Aug 29 2014 - 15:54:26 EST
We have a large university system in the UK that is experiencing
very long delays modprobing the driver for a specific I/O device.
The delay is from 8-10 minutes per device and there are 31 devices
in the system. This 4 to 5 hour delay in starting up those I/O
devices is very much a burden on the customer.
There are two causes for requiring a restart/reload of the drivers.
First is periodic preventive maintenance (PM) and the second is if
any of the devices experience a fatal error. Both of these trigger
this excessively long delay in bringing the system back up to full
The problem was tracked down to a very slow IOREMAP operation and
the excessively long ioresource lookup to insure that the user is
not attempting to ioremap RAM. These patches provide a speed up
to that function.
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