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charset="UTF-8" X-Rspamd-Queue-Id: CE3E2180008 X-Stat-Signature: znpepxwgjqh5sgx9rywwz7ecyt6e8ukf X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1771872949-177775 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > > - Is 64 bits really needed for reverse mapping? For the context, reverse > > mapping here is a swap entry recorded in a lower / physical device > > pointing to the ghost / virtual device. > > I think you can compact this a bit. Swap space itself is not fully 64 > bits right? > > Just not sure if the juice is worth the squeeze to save a couple of > bits here and there, especially if the reverse mapping is already > dynamic :) I think we should actually revisit the need for a reverse mapping to begin with. For swapoff, we can probably scan the virtual swap space looking for entries that belong to the backend being swapped off. Not as efficient as a reverse map, but still better than the status quo of scanning page tables. I don't think optimizing for swapoff is worth the consistent overhead. The other use cases are probably cluster readahead and swapcache-only reclaim, and I think both of these can also be revisited.