Merge pull request #242 from simar7/patch-4

Update timers-1.md

Timers/timers-1.md

@@ -6,7 +6,7 @@ Introduction
 
 This is yet another post that opens new chapter in the [linux-insides](http://0xax.gitbooks.io/linux-insides/content/) book. The previous [part](https://0xax.gitbooks.io/linux-insides/content/SysCall/syscall-4.html) was a list part of the chapter that describes [system call](https://en.wikipedia.org/wiki/System_call) concept and now time is to start new chapter. As you can understand from the post's title, this chapter will be devoted to the `timers` and `time management` in the Linux kernel. The choice of topic for the current chapter is not accidental. Timers and generally time management are very important and widely used in the Linux kernel. The Linux kernel uses timers for various tasks, different timeouts for example in [TCP](https://en.wikipedia.org/wiki/Transmission_Control_Protocol) implementation, the kernel must know current time, scheduling asynchronous functions, next event interrupt scheduling and many many more.
 
-So, we will start to learn implementation of the different time management related stuff in this part. We will see different types of timers and how do different Linux kernel subsystems use them. As always we will start from the earliest part of the Linux kernel and will go through initialization process of the Linux kernel. We already did it in the special [chapter](https://0xax.gitbooks.io/linux-insides/content/Initialization/index.html) which describes initialization process of the Linux kernel, but as you may remember we missied some things there. And one of these is initialization of timers.
+So, we will start to learn implementation of the different time management related stuff in this part. We will see different types of timers and how do different Linux kernel subsystems use them. As always we will start from the earliest part of the Linux kernel and will go through initialization process of the Linux kernel. We already did it in the special [chapter](https://0xax.gitbooks.io/linux-insides/content/Initialization/index.html) which describes initialization process of the Linux kernel, but as you may remember we missied some things there. And one of them is the initialization of timers.
 
 Let's start.
 
@@ -168,7 +168,7 @@ Now we know a little theory about `jiffies` and we can return to the our functio
 The `clocksource` is hardware abstraction for a free-running counter.
 ```
 
-I don't know how about you, but this not full description didn't give me almost anything in understanding of the `clocksource` concept. Let's try to understand what is it, but we will not go deeper because this topic will be described in the separate part in details. The main point of the `clocksource` is timekeeping abstraction or in very simple words - it provides a time value to the kernel. We already know about `jiffies` interface that represents number of ticks that have occurred since the system booted. It represented by the global variable in the Linux kernel and incremented each timer interrupt. The Linux kernel can use `jiffies` for time measurement. So why do we need in separate context like the `clocksource`? Actually different hardware devices provide different clock sources that are widely in their capabilities. The availability of more precise techniques for time intervals measurement is hardware-dependent.
+I'm not sure about you, but that description didn't give a good understanding about the `clocksource` concept. Let's try to understand what is it, but we will not go deeper because this topic will be described in a separate part in much more detail. The main point of the `clocksource` is timekeeping abstraction or in very simple words - it provides a time value to the kernel. We already know about `jiffies` interface that represents number of ticks that have occurred since the system booted. It represented by the global variable in the Linux kernel and incremented each timer interrupt. The Linux kernel can use `jiffies` for time measurement. So why do we need in separate context like the `clocksource`? Actually different hardware devices provide different clock sources that are widely in their capabilities. The availability of more precise techniques for time intervals measurement is hardware-dependent.
 
 For example `x86` has on-chip a 64-bit counter that is called [Time Stamp  Counter](https://en.wikipedia.org/wiki/Time_Stamp_Counter) and its frequency can be equal to processor frequency. Or for example [High Precision Event Timer](https://en.wikipedia.org/wiki/High_Precision_Event_Timer) that consists of a `64-bit` counter of at least `10 MHz` frequency. Two different timers and they are both for `x86`. If we will add timers from other architectures, this only makes this problem more complex. The Linux kernel provides `clocksource` concept to solve the problem.