> On Wednesday, September 01, 2010, KOSAKI Motohiro wrote: > > > === 8< === > > > PM: Marking nosave pages: ...0009f000 - ...000100000 > > > PM: basic memory bitmaps created > > > PM: Syncing filesystems ... done > > > Freezing user space processes ... (elapsed 0.01 seconds) done. > > > Freezing remaining freezable tasks ... (elapsed 0.01 seconds) done. > > > PM: Preallocating image memory... > > > shrink_all_memory start > > > PM: shrink memory: pass=1, req:310171 reclaimed:15492 free:360936 > > > PM: shrink memory: pass=2, req:294679 reclaimed:28864 free:373981 > > > PM: shrink memory: pass=3, req:265815 reclaimed:60311 free:405374 > > > PM: shrink memory: pass=4, req:205504 reclaimed:97870 free:443024 > > > PM: shrink memory: pass=5, req:107634 reclaimed:146948 free:492141 > > > shrink_all_memory: req:107634 reclaimed:146948 free:492141 > > > PM: preallocate_image_highmem 556658 278329 > > > PM: preallocate_image_memory 103139 103139 > > > PM: preallocate_highmem_fraction 183908 556658 760831 -> 183908 > > > === >8 === > > > > Rafael, this log mean hibernate_preallocate_memory() has a bug. > > Well, it works as designed ... > > > It allocate memory as following order. > > 1. preallocate_image_highmem() (i.e. __GFP_HIGHMEM) > > 2. preallocate_image_memory() (i.e. GFP_KERNEL) > > 3. preallocate_highmem_fraction (i.e. __GFP_HIGHMEM) > > 4. preallocate_image_memory() (i.e. GFP_KERNEL) > > > > But, please imazine following scenario (as Vefa's scenario). > > - system has 3GB memory. 1GB is normal. 2GB is highmem. > > - all normal memory is free > > - 1.5GB memory of highmem are used for tmpfs. rest 500MB is free. > > Indeed, that's a memory allocation pattern I didn't anticipate. > > > At that time, hibernate_preallocate_memory() works as following. > > > > 1. call preallocate_image_highmem(1GB) > > 2. call preallocate_image_memory(500M) total 1.5GB allocated > > 3. call preallocate_highmem_fraction(660M) total 2.2GB allocated > > > > then, all of normal zone memory was exhaust. next preallocate_image_memory() > > makes OOM, and oom_killer_disabled makes infinite loop. > > (oom_killer_disabled careless is vmscan bug. I'll fix it soon) > > So, it looks like the problem will go away if we check if there are any normal > pages to allocate from before calling the last preallocate_image_memory()? > > Like in the patch below, perhaps? Looks like fine. but I have one question. hibernate_preallocate_memory() call preallocate_image_memory() two times. Why do you only care latter one? former one seems similar risk. > > The problem is, alloc_pages(__GFP_HIGHMEM) -> alloc_pages(GFP_KERNEL) is > > wrong order. alloc_pages(__GFP_HIGHMEM) may allocate page from lower zone. > > then, next alloc_pages(GFP_KERNEL) lead to OOM. > > > > Please consider alloc_pages(GFP_KERNEL) -> alloc_pages(__GFP_HIGHMEM) order. > > Even though vmscan fix can avoid infinite loop, OOM situation might makes > > big slow down on highmem machine. It seems no good. > > There's a problem with the ordering change that it wouldn't be clear how many > pages to request from the normal zone in step 1 and 3. ok, I see. thanks for good correction my mistake. _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
