# Look Ahead buffer vs Translation Look aside buffer

I know that Translation look aside buffer is used for address translation in paging to achieve better performance.

I came across term called Look Ahead buffer in a document which said it implements Temporal locality.

I tried searching for Look Ahead buffer's but could not get any significant data.

Please help

## 3 Answers

I do not know the exact definitions of TLBs and look-ahead buffers, but here is what I understand about them.

TLBs help make translations from virtual to physical addresses quicker via caching. So, you can see how the TLB is implementing temporal locality (any kind of caching is implementing temporal locality) in some sense.

Look ahead buffers on the other hand come into play when while bringing data from disk to memory. Pages that are explicitly requested may be brought into the disk buffer along with other pages (often selected based on spatial locality to the requested page -- but there are other heuristics that the disk can use). The idea is to not have to go to disk too often. Instead the disk will try to predict what pages will be required in the RAM in the future (hence the term "look-ahead").

Note: I have heard people call the TLB the look-aside buffer and the look-ahead buffer. To me it seems like "translation look-aside buffer" is the correct expansion (because I dont see where any "looking ahead" is happening).

As you have already stated that concept of look-aside buffers are used in TLAB .Similarly the look-ahead buffers have very important usage in data compression techniques ( especially the LZ family of algorithms which are cornerstone of compression techniques ). This algorithm divides the stream into 2 segments. Left segment ( or buffer) is search buffer which contains the symbols already encountered and processed. The right segment is termed look ahead buffer which contains symbols yet to be encoded. An excellent explanation can be found here

yes look-ahead buffer can be implemented by working set algorithm to take care of spatial locality.

• Can you expand on this? Right now, your answer is more of a comment. You could explain what spatial locality is, and it what sense the working set algorithm takes care of it. – Yuval Filmus Sep 7 '18 at 2:44