<ul><li>In the process of reading a file, the CPU execution context will switch from executing a user program to the kernel code.</li><li>The overhead in context switching from user to kernel mode is relatively nominal compared to a context switch between two different processes.</li><li>Kernel memory space can only be accessed in the kernel mode.</li><li>Frequent mode switches can still affect a system’s overall performance.</li><li>When the number of user kernel mode switches increased, it affected the performance of the data store application running on the servers.</li><li>To solve the problem, they had to monitor file changes from kernel space using an eBPF program.</li><li>eBPF runs inside the kernel to monitor file changes by attaching it to the file change syscalls, such as write.</li><li>This new solution no longer affected the performance of the data store server.</li><li>Understanding OS internals can help troubleshoot rare occurrences.</li><li>Learning about nitty-gritty OS internal details can be helpful in rare troubleshooting scenarios.</li></ul>

Context Switching Performance — User vs Kernel modes

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