Prefetches are speculative, where either the SW or HW is trying to load something into the cache in advance without knowing for sure that it will be needed. Demand accesses are driven by program loads and stores and are necessary for the program to proceed. They are both just accesses to the L2, but they're flagged differently in the request. In a real system the cache could choose to deprioritize or even drop prefetches since they're not critical to forward progress, but I don't believe we do that in our models.
On Thu, Dec 18, 2008 at 1:37 PM, Bob Nagel <[email protected]> wrote: > Hello, thanks for your answer Steve, I am very new to this world, and > I do not see the difference between prefecth and demand, can you > please expalin this to me?. For me both are the same just accesses to > the L2. > > Thanks. > > 2008/12/18, Steve Reinhardt <[email protected]>: >> "demand" is the complement of "prefetch". "overall" includes both. >> by default there's no prefetching enabled, which is why they are >> typically the same. >> >> >> On Thu, Dec 18, 2008 at 1:05 PM, Bob Nagel <[email protected]> wrote: >> > Hello, >> > >> > Exploring the statistics genreated for the simulator, I do not >> > understand the difference between this two outputs: >> > >> > system.l2.overall_accesses 482 >> > # number of overall (read+write) accesses >> > >> > system.l2.demand_accesses 482 >> > # number of demand (read+write) accesses >> > >> > What is the difference between overall and demand, can anyone please >> > clarify me this?, thank you. >> >> > _______________________________________________ >> > m5-users mailing list >> > [email protected] >> > http://m5sim.org/cgi-bin/mailman/listinfo/m5-users >> > >> _______________________________________________ >> m5-users mailing list >> [email protected] >> http://m5sim.org/cgi-bin/mailman/listinfo/m5-users >> > _______________________________________________ > m5-users mailing list > [email protected] > http://m5sim.org/cgi-bin/mailman/listinfo/m5-users > _______________________________________________ m5-users mailing list [email protected] http://m5sim.org/cgi-bin/mailman/listinfo/m5-users
