From mboxrd@z Thu Jan  1 00:00:00 1970
From: pratyushpatel.1995@gmail.com (Pratyush Patel)
Date: Tue, 22 Mar 2016 13:08:21 +0530
Subject: hrtimer_clock_base and hrtimer_cpu_base
Message-ID: <CAAnMKKYsazrASEDFST++X4Q-qfT1H3uoAhpt8V2b9chr9uzTiA@mail.gmail.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Hello,

I am unable to understand what exactly "clock_base" and "cpu_base", or
simply "base" means (I am seeking an intuitive idea).

I understand that hrtimer subsystem stores its timers in a red-black
tree data structure, and the node for each timer can be found in
struct hrtimer. And if I understand correctly, these red-black trees
are stored per-CPU, each of which is processed differently, leading to
a "hrtimer_cpu_base"? However, as mentioned in a comment in the
hrtimer.h, the "active" attribute in "hrtimer_clock_base" stores the
root node of the red-black tree. Does this mean that each CPU has
multiple clock_bases, and hence multiple red-black trees? Also, could
someone please let me know, or perhaps point to a relevant resource,
which explains what a "timer_base" means?

Relevant files:
1) http://lxr.free-electrons.com/source/include/linux/hrtimer.h
2) http://lxr.free-electrons.com/source/kernel/time/hrtimer.c

Thank you,
Pratyush