Re: [PATCH 1/1] mm: vmalloc: Optimize vmap_lazy_nr arithmetic when purging each vmap_area

[Andrew Morton]

On Thu, 29 Aug 2024 21:06:33 +0800 Adrian Huang <adrianhuang0701@xxxxxxxxx> wrote:

> From: Adrian Huang <ahuang12@xxxxxxxxxx>
> 
> When running the vmalloc stress on a 448-core system, observe the average
> latency of purge_vmap_node() is about 2 seconds by using the eBPF/bcc
> 'funclatency.py' tool [1].
> 
> ...
>
> 3) The data in column "w/o patch" and "w/ patch"
>      * Unit: micro seconds (us)
>      * Each data is the average of 3-time measurements
> 
>          System        w/o patch (us)   w/ patch (us)    Improvement (%)
>      ---------------   --------------   -------------    -------------
>      72-core server          2194              14            99.36%
>      192-core server       143799            1139            99.21%
>      448-core server      1992122            6883            99.65%
> 

Holy cow.  I'll add cc:stable to this.  Partly because it fixes a
softlockup, partly because holy cow.