Re: [RFC PATCH v4 0/2] mm/zsmalloc: defer object free to per-cpu batches

[Sergey Senozhatsky]

On (26/10/16 09:09), Nhat Pham wrote:
> On Fri, Oct 16, 2026 at 5:10 AM Hongfeng Chen
> <chenhongfeng0212@xxxxxxxxx> wrote:
> >
> > Performance results:
> >
> > ROCK 5B+ (RK3588: 4x Cortex-A55 at 1.8GHz, 4x Cortex-A76 at 2.4GHz,
> > performance governor), single process munmap on A55:
> >
> >   times in ms, speedups over base
> >               Base       Patch1       Patch1+2
> >   size        time    time speedup   time speedup
> >   64MB       13.81    3.62   3.81x   3.28   4.21x
> >   128MB      28.50    7.18   3.97x   6.49   4.39x
> >   192MB      42.19   10.71   3.94x   9.69   4.36x
> >   256MB      56.06   14.26   3.93x   12.89  4.35x
> >   512MB     109.50   28.43   3.85x   25.66  4.27x
> >   1024MB    217.10   56.70   3.83x   51.15  4.24x
> >
> > Same machine, single process munmap on A76:
> >
> >   times in ms, speedups over base
> >               Base       Patch1        Patch1+2
> >   size        time    time speedup    time speedup
> >   64MB        5.59    1.58   3.54x    1.49   3.76x
> >   128MB      11.86    3.16   3.75x    2.95   4.02x
> >   192MB      17.18    4.72   3.64x    4.45   3.86x
> >   256MB      22.89    6.29   3.64x    5.87   3.90x
> >   512MB      45.15   12.52   3.61x   11.64   3.88x
> >   1024MB     89.16   24.75   3.60x   23.12   3.86x
> >
> > x86 (Intel Core i7-14700HX, P-cores locked at 2.1GHz with turbo off),
> > single process munmap:
> >
> >   times in ms, speedups over base
> >               Base       Patch1         Patch1+2
> >   size        time    time speedup    time speedup
> >   64MB        2.87    1.50   1.92x    1.14   2.53x
> >   128MB       6.00    2.93   2.05x    2.21   2.71x
> >   192MB       9.33    4.35   2.15x    3.33   2.80x
> >   256MB      12.51    5.78   2.17x    4.38   2.85x
> >   512MB      24.96   11.39   2.19x    8.62   2.90x
> >   1024MB     50.19   22.78   2.20x   17.05   2.94x
> >
> > 1-4 process munmap of 256MB each:
> >
> >   times in ms, speedups over base
> >               Base       Patch1        Patch1+2
> >   mode        time    time speedup   time speedup
> >   1p         13.18    5.78   2.28x   4.35   3.03x
> >   2p         25.83   14.41   1.79x   4.57   5.65x
> >   3p         35.70   22.14   1.61x   4.68   7.63x
> >   4p         44.25   28.71   1.54x   4.75   9.31x
> 
> The numbers look nice, but I think it's a given that if we measure the
> process whose work is offloaded, we'll see a speedup.
> 
> But would this come at a cost?
> 
> 1. Would memory freeing be slowed down? Could you compare the host
> memory usage over this period of time etc.? Hopefully the parallelism
> would cancel out the extra overhead of setting up the work offloading.

Right, especially interesting what happens if OOM-kill of an app with
a considerable amount of data stored in zsmalloc pool, is not immediately
easing the memory pressure.

[..]
> If it's the former, we should dedicate more time
					^^^^
					and tokens ;)
> towards improving zsmalloc.