linux-kernel - Re: [PATCH resend] memcg: introduce per-memcg reclaim interface

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, 4 Apr 2022 10:44:04 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Roman Gushchin <roman.gushchin@...ux.dev>
Cc:     Yosry Ahmed <yosryahmed@...gle.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Jonathan Corbet <corbet@....net>, Yu Zhao <yuzhao@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Wei Xu <weixugc@...gle.com>, Greg Thelen <gthelen@...gle.com>
Subject: Re: [PATCH resend] memcg: introduce per-memcg reclaim interface

On Fri 01-04-22 09:58:59, Roman Gushchin wrote:
> On Fri, Apr 01, 2022 at 03:49:19PM +0200, Michal Hocko wrote:
> > On Thu 31-03-22 10:25:23, Roman Gushchin wrote:
> > > On Thu, Mar 31, 2022 at 08:41:51AM +0000, Yosry Ahmed wrote:
> > [...]
> > > > - A similar per-node interface can also be added to support proactive
> > > >   reclaim and reclaim-based demotion in systems without memcg.
> > > 
> > > Maybe an option to specify a timeout? That might simplify the userspace part.
> > 
> > What do you mean by timeout here? Isn't
> > timeout $N echo $RECLAIM > ....
> > 
> > enough?
> 
> It's nice and simple when it's a bash script, but when it's a complex
> application trying to do the same, it quickly becomes less simple and
> likely will require a dedicated thread to avoid blocking the main app
> for too long and a mechanism to unblock it by timer/when the need arises.
> 
> In my experience using correctly such semi-blocking interfaces (semi- because
> it's not clearly defined how much time the syscall can take and whether it
> makes sense to wait longer) is tricky.

We have the same approach to setting other limits which need to perform
the reclaim. Have we ever hit that as a limitation that would make
userspace unnecessarily too complex?
-- 
Michal Hocko
SUSE Labs