[Bug 111512] [snb] GPU HANG in gnome-shell (after swap?)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111512

--- Comment #9 from Chris Murphy <bugzilla at colorremedies.com> ---
(In reply to Chris Wilson from comment #7)
> It's definitely the kernel's problem in mishandling resources, there are
> plenty still available, we just aren't getting the pages when they are
> required, as they are required. 

I see this very pronounced in the conventional swap on SSD case above, where
top reports ~60% wa, and while free RAM is low, there's still quite a lot of
swap left. But not a lot of activity compared to the swap on ZRAM case.

Active(file):      94364 kB
$ cat /proc/meminfo                                                             
MemTotal:        8025296 kB                                                     
MemFree:          120132 kB                                                     
MemAvailable:     119600 kB                                                     
Buffers:              84 kB                                                     
Cached:           232996 kB                                                     
SwapCached:       601992 kB                                                     
Active:          6403420 kB                                                     
Inactive:         980736 kB                                                     
Active(anon):    6309056 kB                                                     
Inactive(anon):   914428 kB                                                     
Active(file):      94364 kB                                                     
Inactive(file):    66308 kB
Unevictable:       23220 kB
Mlocked:               0 kB
SwapTotal:       8214524 kB
SwapFree:        3756296 kB
Dirty:               840 kB
Writeback:             0 kB
AnonPages:       6899812 kB
Mapped:           128652 kB
Shmem:             72784 kB
KReclaimable:     116684 kB
Slab:             324752 kB
SReclaimable:     116684 kB
SUnreclaim:       208068 kB
KernelStack:       15296 kB
PageTables:        44364 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    12227172 kB
Committed_AS:   15204776 kB
VmallocTotal:   34359738367 kB
VmallocUsed:       40452 kB
VmallocChunk:          0 kB
Percpu:            20864 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        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:      381944 kB
DirectMap2M:     7917568 kB
[chris at fmac ~]$ 


> Yup. Death-by-swap is an old problem (when the oomkiller doesn't kill you,
> you can die of old age waiting for a response wishing it had). Most of our
> effort is spent trying to minimise the system-wide impact when running at
> max memory (when the caches are regularly reaped), handling swap well has
> been an after thought for a decade.

I've tried quite a lot of variations, different sized swaps, swap on ZRAM, and
zswap. And mostly it seems like rearranging deck chairs. I'm not getting enough
quality data to have any idea which one is even marginally better, there's
always some trade off. I guess I should focus instead on ways of containing
unprivileged fork bombs - better they get mad in their own box than take down
the whole system.

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