From: Roman Gushchin <roman.gushchin@linux.dev>
To: lkp@lists.01.org
Subject: Re: [PATCH 2/3] mm: page_counter: rearrange struct page_counter fields
Date: Mon, 22 Aug 2022 11:27:46 -0700 [thread overview]
Message-ID: <YwPKojTHxV4PFoKn@P9FQF9L96D> (raw)
In-Reply-To: <CALvZod4whYX+0ZuCGgyKuG-Q_9d0g7N_x+=WXOeB_1TM=3Q7vg@mail.gmail.com>
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On Mon, Aug 22, 2022 at 09:04:59AM -0700, Shakeel Butt wrote:
> On Mon, Aug 22, 2022 at 8:15 AM Michal Hocko <mhocko@suse.com> wrote:
> >
> > On Mon 22-08-22 08:06:14, Shakeel Butt wrote:
> > [...]
> > > > > struct page_counter {
> > > > > + /*
> > > > > + * Make sure 'usage' does not share cacheline with any other field. The
> > > > > + * memcg->memory.usage is a hot member of struct mem_cgroup.
> > > > > + */
> > > > > + PC_PADDING(_pad1_);
> > > >
> > > > Why don't you simply require alignment for the structure?
> > >
> > > I don't just want the alignment of the structure. I want different
> > > fields of this structure to not share the cache line. More
> > > specifically the 'high' and 'usage' fields. With this change the usage
> > > will be its own cache line, the read-most fields will be on separate
> > > cache line and the fields which sometimes get updated on charge path
> > > based on some condition will be a different cache line from the
> > > previous two.
> >
> > I do not follow. If you make an explicit requirement for the structure
> > alignement then the first field in the structure will be guarantied to
> > have that alignement and you achieve the rest to be in the other cache
> > line by adding padding behind that.
>
> Oh, you were talking explicitly about _pad1_, yes, we can remove it
> and make the struct cache align. I will do it in the next version.
Yes, please, it caught my eyes too.
With this change:
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Also, can you, please, include the numbers on the additional memory overhead?
I think it still worth it, just think we need to include them for a record.
Thanks!
next prev parent reply other threads:[~2022-08-22 18:27 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-22 0:17 [PATCH 0/3] memcg: optimizatize charge codepath Shakeel Butt
2022-08-22 0:17 ` [PATCH 1/3] mm: page_counter: remove unneeded atomic ops for low/min Shakeel Butt
2022-08-22 0:20 ` Soheil Hassas Yeganeh
2022-08-22 2:39 ` Feng Tang
2022-08-22 9:55 ` Michal Hocko
2022-08-22 10:18 ` Michal Hocko
2022-08-22 14:55 ` Shakeel Butt
2022-08-22 15:20 ` Michal Hocko
2022-08-22 16:06 ` Shakeel Butt
2022-08-23 9:42 ` Michal Hocko
2022-08-22 18:23 ` Roman Gushchin
2022-08-22 0:17 ` [PATCH 2/3] mm: page_counter: rearrange struct page_counter fields Shakeel Butt
2022-08-22 0:24 ` Soheil Hassas Yeganeh
2022-08-22 4:55 ` Shakeel Butt
2022-08-22 13:06 ` Soheil Hassas Yeganeh
2022-08-22 2:10 ` Feng Tang
2022-08-22 4:59 ` Shakeel Butt
2022-08-22 10:23 ` Michal Hocko
2022-08-22 15:06 ` Shakeel Butt
2022-08-22 15:15 ` Michal Hocko
2022-08-22 16:04 ` Shakeel Butt
2022-08-22 18:27 ` Roman Gushchin [this message]
2022-08-22 0:17 ` [PATCH 3/3] memcg: increase MEMCG_CHARGE_BATCH to 64 Shakeel Butt
2022-08-22 0:24 ` Soheil Hassas Yeganeh
2022-08-22 2:30 ` Feng Tang
2022-08-22 10:47 ` Michal Hocko
2022-08-22 15:09 ` Shakeel Butt
2022-08-22 15:22 ` Michal Hocko
2022-08-22 16:07 ` Shakeel Butt
2022-08-22 18:37 ` Roman Gushchin
2022-08-22 19:34 ` Michal Hocko
2022-08-23 2:22 ` Roman Gushchin
2022-08-23 4:49 ` Michal Hocko
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