linux-kernel - Re: [PATCH 2/4] mm: memcontrol: re-use global VM event enum

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 10 Apr 2017 10:13:34 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH 2/4] mm: memcontrol: re-use global VM event enum

On Fri, Apr 07, 2017 at 02:47:02PM +0200, Michal Hocko wrote:
> I do agree that we should share global and memcg specific events constants
> but I am not sure we want to share all of them. Would it make sense to
> reorganize the global enum and put those that are shared to the
> beginning? We wouldn't need the memcg specific translation then.

I'm not sure I follow. Which translation?

> Anyway, two comments on the current implementation.
> 
> On Tue 04-04-17 18:01:46, Johannes Weiner wrote:
> [...]
> > +/* Cgroup-specific events, on top of universal VM events */
> > +enum memcg_event_item {
> > +	MEMCG_LOW = NR_VM_EVENT_ITEMS,
> > +	MEMCG_HIGH,
> > +	MEMCG_MAX,
> > +	MEMCG_OOM,
> > +	MEMCG_NR_EVENTS,
> > +};
> 
> The above should mention that each supported global VM event should
> provide the corresponding translation
> 
> [...]
> 
> here...
> > +/* Universal VM events cgroup1 shows, original sort order */
> > +unsigned int memcg1_events[] = {
> > +	PGPGIN,
> > +	PGPGOUT,
> > +	PGFAULT,
> > +	PGMAJFAULT,
> > +};
> > +
> > +static const char *const memcg1_event_names[] = {
> > +	"pgpgin",
> > +	"pgpgout",
> > +	"pgfault",
> > +	"pgmajfault",
> > +};
> 
> the naming doesn't make it easier to undestand why we need this.
> global2memcg_event?

This is just to keep the file order consistent. It could have been
done like memory.stat in cgroup2, where we simply do

   seq_printf(s, "pgmajfault %lu\n", stat[PGMAJFAULT]);

but I didn't want to change the v1 code too much. So these two arrays
are just a sorted list of global VM events shown in v1's memory.stat.