Thursday, April 7, 2011

memory^thread creation - kernel always involved?

memory - see post on new-and-syscall-wholesale^retail (http://bigblog.tanbin.com/2010/02/new-and-syscall-wholesaleretail.html)
A) wholesale -  malloc grabbing from kernel [1]
B) retail - malloc to divvy up to host application. Note malloc is an /embedded-library/ and not a separate process. It is in the code section of one application only.

thread -
A) if you create a kernel thread or create a Solaris LWP, then you probably call into kernel[1]
A2) when your kernel thread is scheduled, it's scheduled by kernel. Your application can't interfere with it
B) if you create a userland thread, then the thread library does it without kernel
B2) when your userland thread is schedule, it's scheduled by the thread library. Kernel is unaware of userland threads and can't schedule them.

Note the thread library could be bundled with the OS, just like malloc, but it doesn't have to be. Half the time, these libraries can serve user applications without calling into the kernel.

[1] since memory is a hardware resource protected by OS

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