Peter Wemm to change FreeBSD/i386 segment limit to 4GB
To quote him:
“Change the segment limits to 4GB, we set the user accessible bit on all of the kernel address space already. Intel recommend this anyway, because using a non-4GB limit adds an additional clock cycle to address generation. We were able to install 4GB segments into the LDT, so any limits we imposed on %cs and %ds were academic anyway. More importantly, this allows us to make a page in the kernel readable to user applications, for holding things like the signal trampoline and other fun things.”
This change has drastically improved potential performance, and flexibility.
在线阅读本文并参与讨论 delphij's Chaos https://blog.delphij.net/posts/2005/04/peter-wemm-to-c/