On Wed, Dec 13, 2023 at 3:34 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > > On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou > <zhouchengming@xxxxxxxxxxxxx> wrote: > > > > Change the dstmem size from 2 * PAGE_SIZE to only one page since > > we only need at most one page when compress, and the "dlen" is also > > PAGE_SIZE in acomp_request_set_params(). If the output size > PAGE_SIZE > > we don't wanna store the output in zswap anyway. > > > > So change it to one page, and delete the stale comment. > > I couldn't find the history of why we needed 2 * PAGE_SIZE, it would > be nice if someone has the context, perhaps one of the maintainers. It'd be very nice indeed. > > One potential reason is that we used to store a zswap header > containing the swap entry in the compressed page for writeback > purposes, but we don't do that anymore. Maybe we wanted to be able to > handle the case where an incompressible page would exceed PAGE_SIZE > because of that? It could be hmm. I didn't study the old zswap architecture too much, but it has been 2 * PAGE_SIZE since the time zswap was first merged last I checked. I'm not 100% comfortable ACK-ing the undoing of something that looks so intentional, but FTR, AFAICT, this looks correct to me.
