SSIS Performance tuning Suppose my system has 8GB RAM and I have installed SQL Server 2012 on it along with the DataTools. Sql server engine uses 6GB memory. Will the SSIS uses remaning memory apart from 6GB or it uses 6GB? 
Also is there a way to count the number of buffers used and the records accomodated in each buffer and the size of the buffer?

If am not wrong buffer refers to the RAM memory?﻿
SSIS will use as much memory as it needs. If there is not enough physical DRAM on the box, it will take it from the page file (which generally results in a big slowdown)

The memory for running SSIS does not come out of the SQL Server memory space, it comes out of the memory that is left on the box after SQL Server has taken what it wants. In your case, this would be 2GB. Remember that out of those 2GB, you will also need space for the OS and another other applications running on the box.

In other words, think of SSIS just like any other application - not as part of SQL Server (even though it installs with it).