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| /gem5/src/arch/x86/ | ||
| H A D | faults.hh | diff 11218:d135bc832ffe Mon Nov 16 06:08:00 EST 2015 Swapnil Haria <swapnilh@cs.wisc.edu> x86: Invalidating TLB entry on page fault As per the x86 architecture specification, matching TLB entries need to be invalidated on a page fault. For instance, after a page fault due to inadequate protection bits on a TLB hit, the TLB entry needs to be invalidated. This behavior is clearly specified in the x86 architecture manuals from both AMD and Intel. This invalidation is missing currently in gem5, due to which linux kernel versions 3.8 and up cannot be simulated efficiently. This is exposed by a linux optimisation in commit e4a1cc56e4d728eb87072c71c07581524e5160b1, which removes a tlb flush on updating page table entries in x86. Testing: Linux kernel versions 3.8 onwards were booting very slowly in FS mode, due to repeated page faults (~300000 before the first print statement in a bash file). Ensured that page fault rate drops drastically and observed reduction in boot time from order of hours to minutes for linux kernel v3.8 and v3.11 |
| H A D | faults.cc | diff 11218:d135bc832ffe Mon Nov 16 06:08:00 EST 2015 Swapnil Haria <swapnilh@cs.wisc.edu> x86: Invalidating TLB entry on page fault As per the x86 architecture specification, matching TLB entries need to be invalidated on a page fault. For instance, after a page fault due to inadequate protection bits on a TLB hit, the TLB entry needs to be invalidated. This behavior is clearly specified in the x86 architecture manuals from both AMD and Intel. This invalidation is missing currently in gem5, due to which linux kernel versions 3.8 and up cannot be simulated efficiently. This is exposed by a linux optimisation in commit e4a1cc56e4d728eb87072c71c07581524e5160b1, which removes a tlb flush on updating page table entries in x86. Testing: Linux kernel versions 3.8 onwards were booting very slowly in FS mode, due to repeated page faults (~300000 before the first print statement in a bash file). Ensured that page fault rate drops drastically and observed reduction in boot time from order of hours to minutes for linux kernel v3.8 and v3.11 |
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