On 8/27/2014 4:06 PM, Andrew Morton wrote: > On Wed, 27 Aug 2014 17:59:27 -0500 Mike Travis <travis@xxxxxxx> wrote: > >> >> 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. > > That's nuts. Exactly! The customer was (as expected) not terribly pleased... :) > >> 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 >> capability. >> >> 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. > > With what result? > Early measurements on our in house lab system (with far fewer cpus and memory) shows about a 60-75% increase. They have a 31 devices, 3000+ cpus, 10+Tb of memory. We have 20 devices, 480 cpus, ~2Tb of memory. I expect their ioresource list to be about 5-10 times longer. [But their system is in production so we have to wait for the next scheduled PM interval before a live test can be done.] -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>