Messages in this thread | | | Date | Fri, 29 Mar 2024 13:44:57 -0400 | From | Johannes Weiner <> | Subject | Re: [RFC PATCH 5/9] mm: zswap: remove zswap_same_filled_pages_enabled |
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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@google.com> wrote: > >> > >> On Thu, Mar 28, 2024 at 12:11 PM Johannes Weiner <hannes@cmpxchg.org> 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@google.com> > >>> > >>> Acked-by: Johannes Weiner <hannes@cmpxchg.org> > >>> > >>> 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@oracle.com/ > > > > 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.
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