> The problem with platform threads is that they are expensive from a lot of points of view. First, they are costly to create. Whenever a platform thread is made, the OS must allocate a large amount of memory (megabytes) in the stack to store the thread context, native, and Java call stacks. This is due to the not resizable nature of the stack. Moreover, whenever the scheduler preempts a thread from execution, this enormous amount of memory must be moved around.

There are a few issues and inaccuracies in this statement.

While it is true that platform threads can be expensive in terms of resources, the claim that the OS must allocate "megabytes" of memory for the stack is an exaggeration. The actual size of the stack depends on the operating system and the specific implementation, but typical default values range from a few dozen kilobytes to a few hundred kilobytes, not megabytes.

The statement implies that the entire stack is moved around when the scheduler preempts a thread from execution. This is not accurate. When a thread is preempted, the operating system saves the context of the thread, which is a relatively small amount of data, including the values of the CPU registers and the program counter. The stack itself is not moved around during this process.

It is not correct to say that the stack is "not resizable." While the default stack size is set by the operating system, many programming languages and operating systems allow you to specify the stack size when creating a new thread. However, it is true that once a thread has been created, its stack size typically cannot be changed.

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