linux-kernel - Re: [PATCH] proc: add percpu populated pages count to meminfo

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Message-ID: <20180807152107.GB59704@dennisz-mbp.dhcp.thefacebook.com>
Date:   Tue, 7 Aug 2018 08:21:09 -0700
From:   Dennis Zhou <dennisszhou@...il.com>
To:     Christopher Lameter <cl@...ux.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <guro@...com>, kernel-team@...com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] proc: add percpu populated pages count to meminfo

Hi Christopher,

On Tue, Aug 07, 2018 at 02:12:06PM +0000, Christopher Lameter wrote:
> On Mon, 6 Aug 2018, Dennis Zhou wrote:
> >  	show_val_kb(m, "VmallocUsed:    ", 0ul);
> >  	show_val_kb(m, "VmallocChunk:   ", 0ul);
> > +	show_val_kb(m, "PercpuPopulated:", pcpu_nr_populated_pages());
> 
> Populated? Can we avoid this for simplicities sake: "Percpu"?

Yeah, I've dropped populated.

> 
> We do not count pages that are not present elsewhere either and those
> counters do not have "populated" in them.

I see, that makes sense. I think I was trying to keep an external
distinction between what we reserve and what we actually have populated
that really isn't useful outside of playing with the allocator itself.

> >  int pcpu_nr_empty_pop_pages;
> >
> > +/*
> > + * The number of populated pages in use by the allocator, protected by
> > + * pcpu_lock.  This number is kept per a unit per chunk (i.e. when a page gets
> > + * allocated/deallocated, it is allocated/deallocated in all units of a chunk
> > + * and increments/decrements this count by 1).
> > + */
> > +static int pcpu_nr_populated;
> 
> pcpu_nr_pages?
> 

I'd rather keep it as pcpu_nr_populated because internally in pcpu_chunk
we maintain nr_pages and nr_populated. That way we keep the same meaning
at the chunk and global level.

Thanks,
Dennis