On 05.01.17 12:08:20, Will Deacon wrote: > On Thu, Jan 05, 2017 at 12:24:07PM +0100, Robert Richter wrote: > > On 04.01.17 14:02:23, Will Deacon wrote: > > > Using early_pfn_valid feels like a bodge to me, since having pfn_valid > > > return false for something that early_pfn_valid says is valid (and is > > > therefore initialised in the memmap) makes the NOMAP semantics even more > > > confusing. > > > > The concern I have had with HOLES_IN_ZONE is that it enables > > pfn_valid_within() for arm64. This means that each pfn of a section is > > checked which is done only once for the section otherwise. With up to > > 2^18 pages per section we traverse the memblock list by that factor > > more often. There could be a performance regression. > > There could be, but we're trying to fix a bug here. I wouldn't have > thought that walking over pfns like that is done very often. The bug happens on a small number of machines depending on the memory layout. The fix affects all systems. And right know the impact is unclear. > > I haven't numbers yet, since the fix causes another kernel crash. And, > > this is the next problem I have. The crash doesn't happen otherwise. So, > > either it uncovers another bug or the fix is incomplete. Though the > > changes look like it should work. This needs more investigation. > > I really can't see how the fix causes a crash, and I couldn't reproduce > it on any of my boards, nor could any of the Linaro folk afaik. Are you > definitely running mainline with just these two patches from Ard? Yes, just both patches applied. Various other solutions were working. -Robert -- 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>