On Tue, Dec 20, 2022 at 11:15:00PM +0500, Muhammad Usama Anjum wrote: > Hi Peter, Hi, Muhammad, [...] > Nothing has changed for the userspace. But when the default soft-dirty > feature always updates the soft-dirty flag in the PTEs regardless of > VM_SOFTDIRTY is set or not But it was not? I don't see why the pte flags must be considered at all if VM_SOFTDIRTY is set in existing code base, or before this patch. > why does other components of the mm stop caring for soft-dirty flag in > the PTE when VM_SOFTDIRTY is set? > > > > > Your approach introduced PAGEMAP_NO_REUSED_REGIONS but that special > > information is not remembered in vma, IIUC that's why you find things > > messed up. Fundamentally, it's because you're trying to reuse soft-dirty > > design but it's not completely soft-dirty anymore. > Correct, that's why I'm trying to find a way to correct the soft-dirty > support instead of using anything else. We should try and correct it. I've > sent a RFC to track the soft-dirty flags for sub regions in the VMA. Note that I'm not against the change if that's servicing the purpose of the enhancement you're proposing. But again I wouldn't use "correct" as the word here because I still didn't see anything wrong with the old code. so IMHO the extra complexity on handling VM_SOFTDIRTY (even if to drop it and replace with other structures to maintain ranged soft-dirty) needs to be justified along with the feature introduced, not be justified as a fix. Thanks, -- Peter Xu
