On Tue, Feb 11, 2020 at 3:23 PM Luigi Semenzato <semenzato@xxxxxxxxxx> wrote: > > On Tue, Feb 11, 2020 at 11:50 AM Chris Murphy <lists@xxxxxxxxxxxxxxxxx> wrote: > > > > Original thread: > > https://lore.kernel.org/linux-mm/CAA25o9RSWPX8L3s=r6A+4oSdQyvGfWZ1bhKfGvSo5nN-X58HQA@xxxxxxxxxxxxxx/ > > > > This whole thread is a revelation. I have no doubt most users have no > > idea that hibernation image creation is expected to fail if more than > > 50% RAM is used. Please bear with me while I ask some possibly > > rudimentary questions to ensure I understand this in simple terms. > > To be clear, I am not completely sure of this. Other developers are > not in agreement with this (as you can see from the thread). However, > I can easily and consistently reproduce the memory allocation failure > when anon is >50% of total. According to others, the image allocation > should reclaim pages by forcing anon pages to swap. I don't > understand if/how the swap partition accommodates both swapped pages > and the hibernation image, but in any case, in my experiments, I > allocate a swap disk the same size of RAM, which should be sufficient > (again, according to the threads). I'm testing with this method: # echo reboot > /sys/power/disk # echo disk > /sys/power/state About 2/3rd of the time on a test system, hibernation entry fails. It's fatal. The last journal entry is: [ 349.732372] PM: hibernation: hibernation entry Screen is blank, system gets hot, fans go to high, and it doesn't recover after 15 minutes. After forcing power off and rebooting, there is no hibernation signature reported in the swap partition so I don't think the kernel every reached reboot. Shifting over to a qemu-kvm with pm support enabled, this is working. If I fill up pretty much all of RAM and a small amount of swap is used, the above two commands succeed, the VM reboots, and the hibernation image is resumed without error. AnonPages is 73% of total. Upon successful resume, it appears quite a lot of pages were pushed to swap. It looks like about 1GiB was paged out. Before hibernation: $ cat /proc/meminfo MemTotal: 2985944 kB MemFree: 148376 kB MemAvailable: 220428 kB Buffers: 172 kB Cached: 366100 kB SwapCached: 4632 kB Active: 1962088 kB Inactive: 592576 kB Active(anon): 1842560 kB Inactive(anon): 467904 kB Active(file): 119528 kB Inactive(file): 124672 kB Unevictable: 1628 kB Mlocked: 1628 kB SwapTotal: 3117052 kB SwapFree: 2899952 kB Dirty: 6248 kB Writeback: 0 kB AnonPages: 2187236 kB Mapped: 245800 kB Shmem: 120504 kB KReclaimable: 58016 kB Slab: 203260 kB SReclaimable: 58016 kB SUnreclaim: 145244 kB KernelStack: 13712 kB PageTables: 23364 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 4610024 kB Committed_AS: 6019396 kB VmallocTotal: 34359738367 kB VmallocUsed: 27528 kB VmallocChunk: 0 kB Percpu: 4016 kB HardwareCorrupted: 0 kB AnonHugePages: 0 kB ShmemHugePages: 0 kB ShmemPmdMapped: 0 kB FileHugePages: 0 kB FilePmdMapped: 0 kB CmaTotal: 0 kB CmaFree: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 0 kB DirectMap4k: 238332 kB DirectMap2M: 2904064 kB After resume: [chris@vm ~]$ cat /proc/meminfo MemTotal: 2985944 kB MemFree: 1007132 kB MemAvailable: 1069576 kB Buffers: 76 kB Cached: 400464 kB SwapCached: 296112 kB Active: 755856 kB Inactive: 955624 kB Active(anon): 731668 kB Inactive(anon): 683352 kB Active(file): 24188 kB Inactive(file): 272272 kB Unevictable: 1632 kB Mlocked: 1632 kB SwapTotal: 3117052 kB SwapFree: 1874788 kB Dirty: 2716 kB Writeback: 0 kB AnonPages: 1182108 kB Mapped: 225352 kB Shmem: 102480 kB KReclaimable: 48968 kB Slab: 183104 kB SReclaimable: 48968 kB SUnreclaim: 134136 kB KernelStack: 14000 kB PageTables: 22924 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 4610024 kB Committed_AS: 5937732 kB VmallocTotal: 34359738367 kB VmallocUsed: 27800 kB VmallocChunk: 0 kB Percpu: 4016 kB HardwareCorrupted: 0 kB AnonHugePages: 0 kB ShmemHugePages: 0 kB ShmemPmdMapped: 0 kB FileHugePages: 0 kB FilePmdMapped: 0 kB CmaTotal: 0 kB CmaFree: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Hugetlb: 0 kB DirectMap4k: 238332 kB DirectMap2M: 2904064 kB $ There must be some other cause for the 50% limitation. Is it possible it only starts once there's a certain amount of RAM present? e.g. maybe it can only page out 4GiB of Anon pages to swap? And after that point if at least 50% RAM isn't available, hibernation image creation fails? -- Chris Murphy
