linux-kernel - Re: [PATCH RFC 01/10] rcu: Make CONFIG

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Message-ID: <20180809074523.GA16149@kroah.com>
Date:   Thu, 9 Aug 2018 09:45:23 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Dave Chinner <david@...morbit.com>,
        Michal Hocko <mhocko@...nel.org>,
        Kirill Tkhai <ktkhai@...tuozzo.com>, akpm@...ux-foundation.org,
        rafael@...nel.org, viro@...iv.linux.org.uk,
        darrick.wong@...cle.com, paulmck@...ux.vnet.ibm.com,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        hughd@...gle.com, shuah@...nel.org, robh@...nel.org,
        ulf.hansson@...aro.org, aspriel@...il.com,
        vivek.gautam@...eaurora.org, robin.murphy@....com, joe@...ches.com,
        heikki.krogerus@...ux.intel.com, sfr@...b.auug.org.au,
        vdavydov.dev@...il.com, chris@...is-wilson.co.uk,
        penguin-kernel@...ove.SAKURA.ne.jp, aryabinin@...tuozzo.com,
        ying.huang@...el.com, shakeelb@...gle.com, jbacik@...com,
        mingo@...nel.org, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH RFC 01/10] rcu: Make CONFIG_SRCU unconditionally enabled

On Wed, Aug 08, 2018 at 05:07:08PM -0700, Matthew Wilcox wrote:
> On Thu, Aug 09, 2018 at 07:31:25AM +1000, Dave Chinner wrote:
> > IMO, we've had enough recent bugs to deal with from shrinkers being
> > called before the filesystem is set up and from trying to handle
> > allocation errors during setup. Do we really want to make shrinker
> > shutdown just as prone to mismanagement and subtle, hard to hit
> > bugs? I don't think we do - unmount is simply not a critical
> > performance path.
> 
> It's never been performance critical for me, but I'm not so sure that
> there aren't container workloads which unmount filesystems multiple
> times per second.

What?  Why would they do that?  Who cares about tear-down speeds?  Start
up speeds I can kind of understand...