On Fri, Mar 29, 2024 at 03:02:10PM +0100, Maciej S. Szmigiero wrote: > On 29.03.2024 03:14, Yosry Ahmed wrote: > > On Thu, Mar 28, 2024 at 1:06 PM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > >> > >> On Thu, Mar 28, 2024 at 12:11 PM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > >>> > >>> On Mon, Mar 25, 2024 at 11:50:13PM +0000, Yosry Ahmed wrote: > >>>> There is no logical reason to refuse storing same-filled pages more > >>>> efficiently and opt for compression. Remove the userspace knob. > >>>> > >>>> Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx> > >>> > >>> Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > >>> > >>> I also think the non_same_filled_pages_enabled option should go > >>> away. Both of these tunables are pretty bizarre. > >> > >> Happy to remove both in the next version :) > > > > I thought non_same_filled_pages_enabled was introduced with the > > initial support for same-filled pages, but it was introduced > > separately (and much more recently): > > https://lore.kernel.org/all/7dbafa963e8bab43608189abbe2067f4b9287831.1641247624.git.maciej.szmigiero@xxxxxxxxxx/ > > > > I am CCing Maciej to hear more about the use case for this. > > Thanks for CCing me. > > I introduced "non_same_filled_pages_enabled" a few years ago to > enable using zswap in a lightweight mode where it is only used for > its ability to store same-filled pages effectively. But all the pages it rejects go to disk swap instead, which is much slower than compression... > As far as I remember, there were some interactions between full > zswap and the cgroup memory controller - like, it made it easier > for an aggressive workload to exceed its cgroup memory.high limits. Ok, that makes sense! A container fairness measure, rather than a performance optimization. Fair enough, but that's moot then with cgroup accounting of the backing memory, f4840ccfca25 ("zswap: memcg accounting"). Thanks for prodiving context.
