Tested with this kernel module: http://bsdbackstore.eu/misc/oomk/ It requires 2 parameters: the first one is the amount of memory you want to allocate with page_frag_alloc(), the second one is the size of the fragment I tested it on a machine with ~7Gb of free memory. Without the patch: ------------------------------------------------- 3Gb of memory will be used with frag size = 1024 byte. No issue: #insmod oomk.ko memory_size_gb=3 fragsize=1024 [ 177.875107] Test begins, memory size = 3 fragsize = 1024 [ 177.974538] Test completed! 10 Gb of memory, 1024 byte frag. page allocation failure but the kernel handles it and doesn't crash: #insmod oomk.ko memory_size_gb=10 fragsize=1024 [ 215.104801] Test begins, memory size = 10 fragsize = 1024 [ 215.227854] insmod: page allocation failure: order:0, mode:0xa20(GFP_ATOMIC), nodemask=(null),cpuset=/,mems_allowed=0 [ 215.230231] CPU: 1 PID: 1738 Comm: insmod Kdump: loaded Tainted: G OE --------- --- 5.14.0-124.kpq0.el9.x86_64 #1 [ 215.232344] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [ 215.233523] Call Trace: [ 215.234001] dump_stack_lvl+0x34/0x44 [ 215.234894] warn_alloc+0x134/0x160 [ 215.235592] __alloc_pages_slowpath.constprop.0+0x809/0x840 [ 215.236687] ? get_page_from_freelist+0xc6/0x500 [ 215.237569] __alloc_pages+0x1fa/0x230 [ 215.238381] page_frag_alloc_align+0x16c/0x1a0 [...] [ 215.315722] allocation number 7379888 failed! [ 215.426227] Test completed! 10Gb, 4097 byte frag. Kernel crashes: #insmod oomk.ko memory_size_gb=10 fragsize=4097 [ 623.461505] BUG: Bad page state in process insmod pfn:10a80c [ 623.462634] page:000000000654dc14 refcount:0 mapcount:0 mapping:000000007a56d6cd index:0x0 pfn:0x10a80c [ 623.464401] memcg:ffff900343a5b501 [ 623.465058] aops:0xffff9003409e5d38 with invalid host inode 00003524480055f0 [ 623.466394] flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff) [ 623.467632] raw: 0017ffffc0000000 dead000000000100 dead000000000122 ffff900346cf2900 [ 623.469069] raw: 0000000000000000 0000000000100010 00000000ffffffff ffff900343a5b501 [ 623.470521] page dumped because: page still charged to cgroup [...] [ 626.632838] general protection fault, probably for non-canonical address 0xdead000000000108: 0000 [#1] PREEMPT SMP PTI [ 626.633913] ------------[ cut here ]------------ [ 626.639981] CPU: 0 PID: 722 Comm: agetty Kdump: loaded Tainted: G B OE --------- --- 5.14.0-124.kpq0.el9.x86_64 #1 [ 626.640923] WARNING: CPU: 1 PID: 22 at mm/slub.c:4566 __ksize+0xc4/0xe0 [ 626.645018] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011 [ 626.645021] RIP: 0010:___slab_alloc+0x1b7/0x5c0 ------------------------------------------ With the patch the kernel doesn't crash: #insmod oomk.ko memory_size_gb=10 fragsize=4097 [ 4859.358496] Test begins, memory size = 10 fragsize = 4097 [ 4859.459674] allocation number 607754 failed! [ 4859.495489] Test completed! #insmod oomk.ko memory_size_gb=10 fragsize=40000 [ 8428.021491] Test begins, memory size = 10 fragsize = 40000 [ 8428.024308] allocation number 0 failed! [ 8428.025709] Test completed! Maurizio
