Re: [PATCH v6 1/2] memory_hotplug: Free pages as higher order

[Arun KS]

On 2018-11-06 19:36, Michal Hocko wrote:
> On Tue 06-11-18 11:33:13, Arun KS wrote:
> > When free pages are done with higher order, time spend on
> > coalescing pages by buddy allocator can be reduced. With
> > section size of 256MB, hot add latency of a single section
> > shows improvement from 50-60 ms to less than 1 ms, hence
> > improving the hot add latency by 60%. Modify external
> > providers of online callback to align with the change.
> >
> > This patch modifies totalram_pages, zone->managed_pages and
> > totalhigh_pages outside managed_page_count_lock. A follow up
> > series will be send to convert these variable to atomic to
> > avoid readers potentially seeing a store tear.
>
> Is there any reason to rush this through rather than wait for counters
> conversion first?

Sure Michal.

Conversion patch, https://patchwork.kernel.org/cover/10657217/ is 
currently incremental to this patch. I ll change the order. Will wait 
for preparatory patch to settle first.

Regards,
Arun.

> The patch as is looks good to me - modulo atomic counters of course. I
> cannot really judge whether existing updaters do really race in 
> practice
> to take this riskless.
>
> The improvement is nice of course but this is a rare operation and 50ms
> vs 1ms is hardly noticeable. So I would rather wait for the preparatory
> work to settle. Btw. is there anything blocking that? It seems to be
> mostly automated.