Can do mincore warning #78
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Good idea, thank you! |
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As reported by #74, on Kernal 5.2+ mincore does not report correctly if you don't have write permission. Touch and evict still work as expect it's just the reporting that is wrong. This PR adds a runtime
can_do_mincorefunction for__linux__which checks the Kernal version and if the user running the process has write permission to the file. Ifo_verboseand vmtouch can't get accurate information it issues a warning: vmtouch: WARNING: Process does not have write permission, residency chart will not be accurate.Actual kernal check:
https://github.com/torvalds/linux/blob/b7a16c7ad790d0ecb44dcb08a6a75d0d0455ab5f/mm/mincore.c#L181-L195
Example:
[john@machine vmtouch]$ ./vmtouch -v /nvme/arthor/pubchem.smi.atdb /nvme/arthor/pubchem.smi.atdb vmtouch: WARNING: Process does not have write permission, residency chart will not be accurate [OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO] 3543272/3543272 Files: 1 Directories: 0 Resident Pages: 3543272/3543272 13G/13G 100% Elapsed: 0.014981 seconds # sudo can see the residency correctly and doesn't get a warning [john@machine vmtouch]$ sudo ./vmtouch -v /nvme/arthor/pubchem.smi.atdb /nvme/arthor/pubchem.smi.atdb [OOOOOOOOOOOOOOOo ] 904352/3543272 Files: 1 Directories: 0 Resident Pages: 904352/3543272 3G/13G 25.5% Elapsed: 0.13137 seconds # allow group/other write access, residency is correct - no warning [john@machine vmtouch]$ sudo chmod ugo+w /nvme/arthor/pubchem.smi.atdb [john@machine vmtouch]$ ./vmtouch -v /nvme/arthor/pubchem.smi.atdb /nvme/arthor/pubchem.smi.atdb [OOOOOOOOOOOOOOOo ] 904352/3543272 Files: 1 Directories: 0 Resident Pages: 904352/3543272 3G/13G 25.5% Elapsed: 0.13547 seconds