Benjamin Herrenschmidt <b...@kernel.crashing.org> writes: > On Thu, 2017-02-09 at 14:49 +1100, Benjamin Herrenschmidt wrote: >> On Thu, 2017-02-09 at 08:28 +0530, Aneesh Kumar K.V wrote: >> > In the kernel we do follow the below sequence in different code >> > paths. >> > pte = ptep_get_clear(ptep) >> > .... >> > set_pte_at(ptep, pte) >> > >> > We do that for mremap, autonuma protection update and softdirty >> > clearing. This >> > implies our optimization to skip a tlb flush when clearing a pte >> > update is >> > not valid, because for DD1 system that followup set_pte_at will be >> > done witout >> > doing the required tlbflush. Fix that by always doing the dd1 style >> > pte update >> > irrespective of new_pte value. In a later patch we will optimize >> > the application >> > exit case. >> >> What about my change to set_pte_at() ? We seem to be overwriting >> valid PTEs, >> shouldn't we deal with that ? > > So the HW guys confirmed that the TLB will never cache a valid entry > that has all permissions clear. That leaves the THP write problem > though.
Which is fixed by the autonuma related changes posted at https://lkml.kernel.org/r/1486609259-6796-1-git-send-email-aneesh.ku...@linux.vnet.ibm.com Right now i am running a kernel compile in loop with parallel perf bench numa mem run to make sure we got most of the details correct. (this is on p8) -aneesh
