Messages in this thread | | | From | Shakeel Butt <> | Date | Wed, 23 Dec 2020 14:08:00 -0800 | Subject | Re: [PATCH v5 2/7] mm: memcontrol: convert NR_ANON_THPS account to pages |
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On Wed, Dec 16, 2020 at 7:45 PM Muchun Song <songmuchun@bytedance.com> wrote: > > Currently we use struct per_cpu_nodestat to cache the vmstat > counters, which leads to inaccurate statistics expecially THP
*especially
> vmstat counters. In the systems with hundreads of processors
*hundreds
> it can be GBs of memory. For example, for a 96 CPUs system, > the threshold is the maximum number of 125. And the per cpu > counters can cache 23.4375 GB in total. > > The THP page is already a form of batched addition (it will > add 512 worth of memory in one go) so skipping the batching > seems like sensible. Although every THP stats update overflows > the per-cpu counter, resorting to atomic global updates. But > it can make the statistics more accuracy for the THP vmstat > counters. > > So we convert the NR_ANON_THPS account to pages. This patch > is consistent with 8f182270dfec ("mm/swap.c: flush lru pvecs > on compound page arrival"). Doing this also can make the unit > of vmstat counters more unified. Finally, the unit of the vmstat > counters are pages, kB and bytes. The B/KB suffix can tell us > that the unit is bytes or kB. The rest which is without suffix > are pages. > > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
I agree with the motivation behind this patch but I would like to see some performance numbers in the commit message. We might agree to pay the price but at least we will know what exactly that cost is.
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