linux-kernel - Re: [PATCH V4 6/6] proc: show MADV

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Message-ID: <20170224214724.GA35601@shli-mbp.local>
Date:   Fri, 24 Feb 2017 13:47:25 -0800
From:   Shaohua Li <shli@...com>
To:     Dave Hansen <dave.hansen@...el.com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <Kernel-team@...com>, <mhocko@...e.com>, <minchan@...nel.org>,
        <hughd@...gle.com>, <hannes@...xchg.org>, <riel@...hat.com>,
        <mgorman@...hsingularity.net>, <akpm@...ux-foundation.org>
Subject: Re: [PATCH V4 6/6] proc: show MADV_FREE pages info in smaps

On Fri, Feb 24, 2017 at 09:08:30AM -0800, Dave Hansen wrote:
> On 02/22/2017 10:50 AM, Shaohua Li wrote:
> > @@ -770,6 +774,7 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
> >  		   "Private_Dirty:  %8lu kB\n"
> >  		   "Referenced:     %8lu kB\n"
> >  		   "Anonymous:      %8lu kB\n"
> > +		   "LazyFree:       %8lu kB\n"
> >  		   "AnonHugePages:  %8lu kB\n"
> >  		   "ShmemPmdMapped: %8lu kB\n"
> >  		   "Shared_Hugetlb: %8lu kB\n"
> 
> I've been as guily of this in the past as anyone, but are we just going
> to keep adding fields to smaps forever?  For the vast, vast, majority of
> folks, this will simply waste the 21 bytes * nr_vmas that it costs us to
> print "LazyFree:       0 kB\n" over and over.
> 
> Should we maybe start a habit of not printing an entry when it's "0 kB"?

Interesting idea! I'd like this is a separate patch if we go this way, because
this is likely to be controversial. That said, sounds there is no reason we
shouldn't do this.

Thanks,
Shaohua