On Thu, Aug 15, 2013 at 02:01:09AM +0200, Rafael J. Wysocki wrote: > On Wednesday, August 14, 2013 02:31:45 PM Seth Jennings wrote: > > Large memory systems (~1TB or more) experience boot delays on the order > > of minutes due to the initializing the memory configuration part of > > sysfs at /sys/devices/system/memory/. > > > > ppc64 has a normal memory block size of 256M (however sometimes as low > > as 16M depending on the system LMB size), and (I think) x86 is 128M. With > > 1TB of RAM and a 256M block size, that's 4k memory blocks with 20 sysfs > > entries per block that's around 80k items that need be created at boot > > time in sysfs. Some systems go up to 16TB where the issue is even more > > severe. > > > > This patch provides a means by which users can prevent the creation of > > the memory block attributes at boot time, yet still dynamically create > > them if they are needed. > > > > This patch creates a new boot parameter, "largememory" that will prevent > > memory_dev_init() from creating all of the memory block sysfs attributes > > at boot time. Instead, a new root attribute "show" will allow > > the dynamic creation of the memory block devices. > > Another new root attribute "present" shows the memory blocks present in > > the system; the valid inputs for the "show" attribute. > > I wonder how this is going to work with the ACPI device object binding to > memory blocks that's in 3.11-rc. Thanks for pointing this out. Yes the walking of the memory blocks in this code will present a problem for the dynamic creation of memory blocks :/ Sounds like there are some other challenges (backward compatibility, no boot paramater) that I'll have to look at as well. Seth > > That stuff will only work if the memory blocks are already there when > acpi_memory_enable_device() runs and that is called from the ACPI namespace > scanning code executed (1) during boot and (2) during hotplug. So I don't > think you can just create them on the fly at run time as a result of a > sysfs write. > > Thanks, > Rafael > -- 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>