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How to track SLAB usage using slub_debug=U
When there is high usage in kernel side, most common reason is high usage in SLAB. As the SLAB memory blocks are all data, it is hard to tell which parts of code was consuming this memory blocks. Fortunately, there is this kernel option slub_debug=U which is saving backtrace of the allocation and freeing calls. […]
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Difference between ‘pgscank/s’ and ‘pgscand/s’
In the sar output like below, there are pgscank and pgscand. In the man page, it says. This description is not much helpful to understand the difference between those two columns. These data are from kernel code which is showing in vmstat. It is basically updated when there’s memory reclaiming. If the reclaiming was happened […]
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5-level paging in KVM
Latest kernels such as RHEL8 and above are supporting 5-level page table. You can check if this is available/enabled by looking at /boot/config-$(uname -r). If you don’t want to use 5-level page table, you can disable that by adding ‘no5lvl’ as a kernel parameter in grub file (/boot/grub2/grubenv) and reboot the system. This 5 level […]
Sungju's Slow Life 