On 04/21/2014 02:24 PM, Dave Hansen wrote: > From: Dave Hansen <[email protected]> > > I think the flush_tlb_mm_range() code that tries to tune the > flush sizes based on the CPU needs to get ripped out for > several reasons: > > 1. It is obviously buggy. It uses mm->total_vm to judge the > task's footprint in the TLB. It should certainly be using > some measure of RSS, *NOT* ->total_vm since only resident > memory can populate the TLB. > 2. Haswell, and several other CPUs are missing from the > intel_tlb_flushall_shift_set() function. Thus, it has been > demonstrated to bitrot quickly in practice. > 3. It is plain wrong in my vm: > [ 0.037444] Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0 > [ 0.037444] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0 > [ 0.037444] tlb_flushall_shift: 6 > Which leads to it to never use invlpg. > 4. The assumptions about TLB refill costs are wrong: > > http://lkml.kernel.org/r/[email protected] > (more on this in later patches) > 5. I can not reproduce the original data: https://lkml.org/lkml/2012/5/17/59 > I believe the sample times were too short. Running the > benchmark in a loop yields times that vary quite a bit. > > Note that this leaves us with a static ceiling of 1 page. This > is a conservative, dumb setting, and will be revised in a later > patch. > > Signed-off-by: Dave Hansen <[email protected]>
Acked-by: Rik van Riel <[email protected]> -- All rights reversed -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
