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--- notiz:pm-hibernation-image-allocation-is-97054-pages-short [2023/07/10 23:48] – gelöscht - Externe Bearbeitung (Unknown date) 127.0.0.1
+++ notiz:pm-hibernation-image-allocation-is-97054-pages-short [2023/07/10 23:48] (aktuell) – ↷ Seitename wurde von notiz:hibenate-memory-management auf notiz:pm-hibernation-image-allocation-is-97054-pages-short geändert clerie
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+====== PM: hibernation: Image allocation is 97054 pages short ======
+I encountered an issue where hibernation on a freshly booted system works, but after a while it failed and the system just came up again.
+I checked dmegs and found the following messages.
+<code>
+[Di Jul 11 06:07:02 2023] PM: hibernation: hibernation entry
+[Di Jul 11 06:07:02 2023] Filesystems sync: 0.011 seconds
+[Di Jul 11 06:07:02 2023] Freezing user space processes
+[Di Jul 11 06:07:02 2023] Freezing user space processes completed (elapsed 0.003 seconds)
+[Di Jul 11 06:07:02 2023] OOM killer disabled.
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x00000000-0x00000fff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x0009e000-0x000fffff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x40000000-0x403fffff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x4652b000-0x4652cfff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x5b72c000-0x5b743fff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x5e4e2000-0x5fffefff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Marking nosave pages: [mem 0x60000000-0xffffffff]
+[Di Jul 11 06:07:02 2023] PM: hibernation: Basic memory bitmaps created
+[Di Jul 11 06:07:02 2023] PM: hibernation: Preallocating image memory
+[Di Jul 11 06:07:03 2023] PM: hibernation: Image allocation is 97054 pages short
+[Di Jul 11 06:07:03 2023] PM: hibernation: Basic memory bitmaps freed
+[Di Jul 11 06:07:03 2023] OOM killer enabled.
+[Di Jul 11 06:07:03 2023] Restarting tasks ... done.
+[Di Jul 11 06:07:03 2023] PM: hibernation: hibernation exit
+</code>
+A similar situation got described in the [[https://forums.gentoo.org/viewtopic-t-1134165-start-0.html|Gentoo Forum]] where a comment references the [[https://www.kernel.org/doc/html/latest/power/pci.html#system-hibernation|Linux Documentation]] which states:
+> The freezing of devices is carried out after enough memory has been freed (at the time of this writing the image creation requires at least 50% of system RAM to be free)
+So I checked with my system and yes, more than 50% of RAM got allocated.
+I wondered why this doesn't work anymore, because in a previous Linux installation hibernation just worked fine, even with full RAM.
+Because all of my systems have enough RAM for their intended use, I tuned swap allocation to a minimum and have set:
+<code bash>
+sysctl vm.swappiness=0
+</code>
+Which is literally a "don't dare using swap" option.
+It is okay, because hibernate can still use the swap as a storage, but it does not get used to out source stuff that usually belongs into RAM.
+When there is enough free RAM for hibernation, then everything is fine.
+When there is not, hibernate usually tries to free some memory in RAM and temporarily moves it to swap to it can pack it's resume image.
+But unfortunately this is not allowed due to swappiness being set to 0.
+As a result, setting swappiness to 1 fixes it, because we still deny usage of swap, but allow it for cases where absolutely no other option exist.
+<code bash>
+sysctl vm.swappiness=1
+</code>