Linux – How to see complete list of processes in top

As there are no answers yet...

I do not have an easy suggestion (like an iotop switch) but if this is important to you then you may write a FUSE module which just remounts the file systems elsewhere (chroot for the process to be examined) and counts the amount of data read / written. That should be a rather easy adaption of existing modules. You may ask the FUSE community which might be the best existing solution to start from. Probably even their demo module will do.

Your confusion stems from mixing two things: (1) keeping the process descriptors organized, and (2) the parent/child relationship.

You don't need the parent/child relationship to decide which process to run next, or (in general) which process to deliver a signal to. So, the Linux task_struct (which I found in linux/sched.h for the 3.11.5 kernel source) has:

struct task_struct __rcu *real_parent; /* real parent process */
struct task_struct __rcu *parent; /* recipient of SIGCHLD, wait4() reports */
/*
 * children/sibling forms the list of my natural children
 */

struct list_head children;  /* list of my children */
struct list_head sibling;   /* linkage in my parent's children list */

You're correct, a tree struct exists for the child/parent relationship, but it seems to be concealed in another list, and a pointer to the parent.

The famed doubly-linked list isn't obvious in the 3.11.5 struct task_struct structure definition. If I read the code correctly, the uncommented struct element struct list_head tasks; is the "organizing" doubly-linked list, but I could be wrong.