Re: Move unused buffers to freelist

As per my understanding Summarization of points raised by you and Andres

which this patch should address to have a bigger win:

1. Bgwriter needs to be improved so that it can help in reducing usage count
and finding next victim buffer
   (run the clock sweep and add buffers to the free list).
2. SetLatch for bgwriter (wakeup bgwriter) when elements in freelist are
less.
3. Split the workdone globallock (Buffreelist) in StrategyGetBuffer
   (a spinlock for the freelist, and an lwlock for the clock sweep).
4. Separate processes for writing dirty buffers and moving buffers to
freelist
5. Bgwriter needs to be more aggressive, logic based on which it calculates
how many buffers it needs to process needs to be improved.
6. There can be contention around buffer mapping locks, but we can focus on
it later
7. cacheline bouncing around the buffer header spinlocks, is there anything
we can do to reduce this?