代写实现操作系统中的Malloc/Free函数，需要做到线程安全。
Introduction
Your task in this assignment is to implement a multithreaded malloc i.e. we
should be able to use it in a multithreaded application. The basic requirement
is of course that it is thread safe, that it still works even if two threads
us it at the same time. This is of course very easy to solve by having one
central lock that protects any data structures that are used by the module.
It is a bit harder to allow multiple threads to actually use the malloc module
at the same time to improve efficiency. This is your task; implement the malloc() and free() procedures in way that allows concurrent access. You
should also provide benchmarks of you system that shows that it is faster (or
shows that it is not worth the trouble).
The implementation
Before you start you should have done the experiments that teach you how to
implement malloc() and free() . Since you will implement a
multithreaded system and provide concurrent updates to shared structures it is
also advisable to have done the experiments that shows how pthread mutex locks
are used. If you can combine this knowledge you should be fine.
Start by implementing a malloc procedure that is protected by one global lock.
Run some benchmarks and describe the performance, this is the system that you
will try to beat.
Think about what strategy that could be best to explore, depending on which
strategy that you choose there will be more or less access to shared data
structures and if you want things to run fast you will have to minimize this.
As an extra challenge you can start to think about a thread local cache. If a
thread does a free on a data structure it might be a good idea to give this
structure back to the same thread instead of to some other thread. This is
tricky to solve since all threads execute the same code, yet they should keep
track of thread local data structures. If you do it right you should see some
improvement in execution speed.
The benchmarks
Start doing benchmarks from day one. It will be much easier to change your
strategy early on if you benchmarks tells you that you’re on the wrong track.
In your presentation you should present benchmarks that shows if your approach
was successful or not. If you have a brilliant idea that you think would work
and the benchmarks proves you wrong, this is also very interesting and might
be the conclusion of your report.
