linux-kernel - Re: [PATCH v3 1/2] net: sched: make default fifo qdiscs appear in the dump

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Message-Id: <20170312.225326.432231730454919673.davem@davemloft.net>
Date:   Sun, 12 Mar 2017 22:53:26 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jikos@...nel.org
Cc:     stephen@...workplumber.org, eric.dumazet@...il.com,
        jhs@...atatu.com, phil@....cc, xiyou.wangcong@...il.com,
        daniel@...earbox.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, jiri@...nulli.us
Subject: Re: [PATCH v3 1/2] net: sched: make default fifo qdiscs appear in
 the dump

From: Jiri Kosina <jikos@...nel.org>
Date: Wed, 8 Mar 2017 16:03:32 +0100 (CET)

> From: Jiri Kosina <jkosina@...e.cz>
> 
> The original reason [1] for having hidden qdiscs (potential scalability
> issues in qdisc_match_from_root() with single linked list in case of large
> amount of qdiscs) has been invalidated by 59cc1f61f0 ("net: sched: convert
> qdisc linked list to hashtable").
> 
> This allows us for bringing more clarity and determinism into the dump by
> making default pfifo qdiscs visible.
> 
> We're not turning this on by default though, at it was deemed [2] too
> intrusive / unnecessary change of default behavior towards userspace.
> Instead, TCA_DUMP_INVISIBLE netlink attribute is introduced, which allows
> applications to request complete qdisc hierarchy dump, including the
> ones that have always been implicit/invisible.
> 
> Singleton noop_qdisc stays invisible, as teaching the whole infrastructure
> about singletons would require quite some surgery with very little gain
> (seeing no qdisc or seeing noop qdisc in the dump is probably setting
> the same user expectation).
> 
> [1] http://lkml.kernel.org/r/1460732328.10638.74.camel@edumazet-glaptop3.roam.corp.google.com
> [2] http://lkml.kernel.org/r/20161021.105935.1907696543877061916.davem@davemloft.net
> 
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>

Applied, thanks Jiri.