mm: mmap: add trace point of vm_unmapped_area

2020-04-02T16:35:30Z

Even on 64 bit kernel, the mmap failure can happen for a 32 bit task. Virtual memory space shortage of a task on mmap is reported to userspace as -ENOMEM. It can be confused as physical memory shortage of overall system. The vm_unmapped_area can be called to by some drivers or other kernel core system like filesystem. In my platform, GPU driver calls to vm_unmapped_area and the driver returns -ENOMEM even in GPU side shortage. It can be hard to distinguish which code layer returns the -ENOMEM. Create mmap trace file and add trace point of vm_unmapped_area. i.e.) 277.156599: vm_unmapped_area: addr=77e0d03000 err=0 total_vm=0x17014b flags=0x1 len=0x400000 lo=0x8000 hi=0x7878c27000 mask=0x0 ofs=0x1 342.838740: vm_unmapped_area: addr=0 err=-12 total_vm=0xffb08 flags=0x0 len=0x100000 lo=0x40000000 hi=0xfffff000 mask=0x0 ofs=0x22 [akpm@linux-foundation.org: prefix address printk with 0x, per Matthew] Signed-off-by: Jaewon Kim Signed-off-by: Andrew Morton Cc: Borislav Petkov Cc: Matthew Wilcox (Oracle) Cc: Michel Lespinasse Cc: Vlastimil Babka Link: http://lkml.kernel.org/r/20200320055823.27089-3-jaewon31.kim@samsung.com Signed-off-by: Linus Torvalds

kernel/include/trace/events/mmap.h, branch linux-5.11.y

mm: mmap: add trace point of vm_unmapped_area