Re: [PATCH v4 0/7] read proc/pid/smaps_rollup under per-vma lock

[Andrew Morton]

On Fri, 11 Sep 2026 12:41:38 -0700 Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote:

> proc/pid/smaps_rollup can be read using the combination of RCU and
> VMA read locks, similar to proc/pid/{maps|smaps|numa_maps}. RCU is
> required to safely traverse the VMA tree and VMA lock stabilizes the
> VMA being processed and the pagetable walk.
> Note that we have to keep the logic to drop mmap_lock on contention
> because even when using per-VMA locks we might have to fall back to
> holding the mmap_lock.

Nice.  Queued, thanks.

The speedups described in [6/7] are significant, although I don't know
how representative Paul's tests are.  Probably not very.

So I don't know how much improvement our users will be seeing from
these changes?

And I don't know how much usage smaps_rollup gets in the real world?


As I've no doubt you know, Sashiko is saying things.  About these
patches and about the current code.  Its pre-existing
clear_soft_dirty_pmd() driveby find looks significant.

	https://sashiko.dev/#/patchset/20260911194145.1781926-1-surenb@xxxxxxxxxx