No, I meant the whole RAM size. You can limit the size by passing mem=XXX boot option, where XXX is the size (e.g. 1G, 512M, etc). The problem of i915 driver is tied with the RAM size. When user-space use more memory and the free page becomes tight, the system tries to swap out, and the i915 driver tries shrink its page lists. The problem seems happening during it.