Scott F. Kaplan sfkaplan@cs.amherst.edu August 1999 Here is a description of the trace format for our page-image "traces", which are really LRU behavior sequences. In case you've never encountered this kind of trace, here's a description: An LRU behavior sequence contains the paging traffic for an LRU memory of some fixed size. So, imagine an M-page memory. For every reference that would miss on that memory, the behavior sequence contains a pair. That is, each record in the behavior sequences contains both the page that was referenced and therefore must be fetched, *and* the page that would be evicted from the M-page LRU memory. Note that these traces were gathered on an Intel x86 machine. If you use these traces for processing on a different architecture, you may have to adjust for a different endianness -- the SPARC architecture is such a processor. Here are the fields for our page-image traces. Note that fields 1, 2, and 3 comprise the fetch component, while fields 4, 5, and 6 comprise the evict component. 1. Compulsory Tag: This is a one character tag that should be either a 'C' or a 'F'. The 'C' indicates that this fault is a compulsory fault---that this page hasn't been referenced before. The 'F' indicates that it is just a regular fault on a page that has been referenced before. 2. Fetched Page Number: A four character hex representation of the page number referenced. 3. Fetched Page Image: A 4096 byte binary copy of the page contents when it was referenced during real execution. 4. Dirtiness Tag: A one character tag that should be 'W', 'R', or 'N'. A 'W' for this tag indicates that the evicted page was written at some point during this trip through the M-page LRU queue, and so it is dirty. An 'R' indicates that the page was only read, and so it is clean. An 'N' indicates that the M-page memory is not full, and no eviction occurred. 5. Evicted Page Number: A four character hex representation of the page number evicted. If field #4 is 'N' (no eviction), then this field is "0000". 6. Evicted Page Image: A 4096 byte binary copy of the page contents, exactly as it would be if evicted from an M-page LRU memory. If field #4 is 'N' (no eviction), then this field does not exist (i.e. its length is zero bytes).