Increased process "memory usage" after upgrading to SLES 12 SP2
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A page in X86 is 4 kilobytes/4096. If only one small function in a library in SP0 [that does not have "do_fault_around"] is used, that is how much RSS that library will get charged.
For SP2, that same function call will map 64 kilobytes/65536, and this will be reflected in Resident Set Size (RSS) and Proportional Set Size (PSS).
The values can be found in /proc/<pid>/smaps.
Note though, that the physical pages are already present in the "page cache", so there is no difference in the actual memory usage here.
The file /sys/kernel/debug/fault_around_bytes does not exist on SLES 12 GA, but on SP2 it exists with a default value of 65536.
In the end the customer was able to restore the memory use characteristics/stats of SP0 on SP2 by
echo 4096 > /sys/kernel/debug/fault_around_bytes
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- Document ID:7021290
- Creation Date: 05-Sep-2017
- Modified Date:03-Mar-2020
- SUSE Linux Enterprise Server
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