Re: [PATCH 0/4] mm/page_alloc: Batch callers of free_pcppages_bulk

[Andrew Morton]

On Fri, 19 Sep 2025 12:52:18 -0700 Joshua Hahn <joshua.hahnjy@xxxxxxxxx> wrote:

> While testing workloads with high sustained memory pressure on large machines
> (1TB memory, 316 CPUs), we saw an unexpectedly high number of softlockups.
> Further investigation showed that the lock in free_pcppages_bulk was being held
> for a long time, even being held while 2k+ pages were being freed [1].

What problems are caused by this, apart from a warning which can
presumably be suppressed in some fashion?

> This causes starvation in other processes for both the pcp and zone locks,
> which can lead to softlockups that cause the system to stall [2].

[2] doesn't describe such stalls.

>
> ...
>
> In our fleet, we have seen that performing batched lock freeing has led to
> significantly lower rates of softlockups, while incurring relatively small
> regressions (relative to the workload and relative to the variation).

"our" == Meta?