linux-kernel - Re: [RFC 02/20] timens: Add timens

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Message-ID: <20180920184510.GC20786@uranus>
Date:   Thu, 20 Sep 2018 21:45:10 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...nvz.org>,
        Adrian Reber <adrian@...as.de>,
        Andy Lutomirski <luto@...nel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jeff Dike <jdike@...toit.com>, Oleg Nesterov <oleg@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        containers@...ts.linux-foundation.org, criu@...nvz.org,
        linux-api@...r.kernel.org, x86@...nel.org
Subject: Re: [RFC 02/20] timens: Add timens_offsets

On Wed, Sep 19, 2018 at 09:50:19PM +0100, Dmitry Safonov wrote:
> From: Andrei Vagin <avagin@...nvz.org>
> 
> Introduce offsets for time namespace. They will contain adjustment
> needed to convert clocks to/from host's.
> 
> Allocate one page for each time namespace that will be premapped into
> userspace with vvar pages.

Is not it too much?! The whole page per each clone(new-time-ns) call.
Moreover everytime it is get explicitly zeroifyed. Don't get me wrong,
maybe I miss something obvious, but additional 4K per process, guys :)