On Mon, 09 Aug 2010 12:53:00 -0500 Nathan Fontenot <nfont@xxxxxxxxxxxxxx> wrote: > This set of patches de-couples the idea that there is a single > directory in sysfs for each memory section. The intent of the > patches is to reduce the number of sysfs directories created to > resolve a boot-time performance issue. On very large systems > boot time are getting very long (as seen on powerpc hardware) > due to the enormous number of sysfs directories being created. > On a system with 1 TB of memory we create ~63,000 directories. > For even larger systems boot times are being measured in hours. And those "hours" are mainly due to this problem, I assume. > This set of patches allows for each directory created in sysfs > to cover more than one memory section. The default behavior for > sysfs directory creation is the same, in that each directory > represents a single memory section. A new file 'end_phys_index' > in each directory contains the physical_id of the last memory > section covered by the directory so that users can easily > determine the memory section range of a directory. What you're proposing appears to be a non-back-compatible userspace-visible change. This is a big issue! It's not an unresolvable issue, as this is a must-fix problem. But you should tell us what your proposal is to prevent breakage of existing installations. A Kconfig option would be good, but a boot-time kernel command line option which selects the new format would be much better. However you didn't mention this issue at all, and it's the most important one. > Updates for version 5 of the patchset include the following: > > Patch 4/8 Add mutex for add/remove of memory blocks > - Define the mutex using DEFINE_MUTEX macro. > > Patch 8/8 Update memory-hotplug documentation > - Add information concerning memory holes in phys_index..end_phys_index. And you forgot to tell us how long those machines boot with the patchset applied, which is the entire point of the patchset! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>