On Thu, Feb 22, 2024 at 01:23:43PM +0700, Nhat Pham wrote: > On Fri, Feb 9, 2024 at 10:27 AM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > > > > I did not perform any sophisticated analysis on these histograms, but > > eyeballing them makes it clear that all allocators have somewhat > > similar latencies. zbud is slightly better than zsmalloc, and z3fold > > is slightly worse than zsmalloc. This corresponds naturally to the > > build times in (a). > > > > (c) Maximum size of the zswap pool > > > > *** zsmalloc *** > > 1,137,659,904 bytes = ~1.13G > > > > *** zbud *** > > 1,535,741,952 bytes = ~1.5G > > > > *** z3fold *** > > 1,151,303,680 bytes = ~1.15G > > > > zbud consumes ~32.7% more memory, and z3fold consumes ~1.8% more > > memory. This makes sense because zbud only stores a maximum of two > > compressed pages on each order-0 page, regardless of the compression > > ratio, so it is bound to consume more memory. > > > > -------------------------------- </Results> -------------------------------- > > > > According to those results, it seems like zsmalloc is superior to > > z3fold in both efficiency and latency. Zbud has a small latency > > advantage, but that comes with a huge cost in terms of memory > > consumption. Moreover, most known users of zswap are currently using > > zsmalloc. Perhaps some folks are using zbud because it was the default > > allocator up until recently. The only known disadvantage of zsmalloc > > is the dependency on MMU. > > > > Based on that, I think it doesn't make sense to keep all 3 allocators > > going forward. I believe we should start with removing either zbud or > > z3fold, leaving only one allocator supporting MMU. Once zsmalloc > > supports !MMU (if possible), we can keep zsmalloc as the only > > allocator. > > > > Thoughts and feedback are highly appreciated. I tried to CC all the > > interested folks, but others feel free to chime in. > > I already voiced my opinion on the other thread, but to reiterate, my > vote is towards deprecating/removing z3fold :) > Unless someone can present a convincing argument/use case/workload, > where z3fold outshines both zbud and zsmalloc, or at least is another > point on the Pareto front of (latency x memory saving). I can re-send the RFC to mark z3fold as deprecated with a reference to the data here or a quote to some of it. Alternatively, we can remove the code directly if we believe there are no users. There were some conflicting opinions last time and I was hoping we can settle them. I am also low key hoping Andrew would chime in at some point with what he prefers (deprecate, remove, or leave as-is).
