From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Ian Kent <raven@themaw.net>
Cc: Tejun Heo <tj@kernel.org>,
Rick Lindsley <ricklind@linux.vnet.ibm.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Andrew Morton <akpm@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
David Howells <dhowells@redhat.com>,
Miklos Szeredi <miklos@szeredi.hu>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement
Date: Tue, 23 Jun 2020 08:02:36 +0200 [thread overview]
Message-ID: <20200623060236.GA3818201@kroah.com> (raw)
In-Reply-To: <2ead27912e2a852bffb1477e8720bdadb591628d.camel@themaw.net>
On Tue, Jun 23, 2020 at 01:09:08PM +0800, Ian Kent wrote:
> On Mon, 2020-06-22 at 20:03 +0200, Greg Kroah-Hartman wrote:
> > On Mon, Jun 22, 2020 at 01:48:45PM -0400, Tejun Heo wrote:
> > > Hello, Ian.
> > >
> > > On Sun, Jun 21, 2020 at 12:55:33PM +0800, Ian Kent wrote:
> > > > > > They are used for hotplugging and partitioning memory. The
> > > > > > size of
> > > > > > the
> > > > > > segments (and thus the number of them) is dictated by the
> > > > > > underlying
> > > > > > hardware.
> > > > >
> > > > > This sounds so bad. There gotta be a better interface for that,
> > > > > right?
> > > >
> > > > I'm still struggling a bit to grasp what your getting at but ...
> > >
> > > I was more trying to say that the sysfs device interface with per-
> > > object
> > > directory isn't the right interface for this sort of usage at all.
> > > Are these
> > > even real hardware pieces which can be plugged in and out? While
> > > being a
> > > discrete piece of hardware isn't a requirement to be a device model
> > > device,
> > > the whole thing is designed with such use cases on mind. It
> > > definitely isn't
> > > the right design for representing six digit number of logical
> > > entities.
> > >
> > > It should be obvious that representing each consecutive memory
> > > range with a
> > > separate directory entry is far from an optimal way of representing
> > > something like this. It's outright silly.
> >
> > I agree. And again, Ian, you are just "kicking the problem down the
> > road" if we accept these patches. Please fix this up properly so
> > that
> > this interface is correctly fixed to not do looney things like this.
>
> Fine, mitigating this problem isn't the end of the story, and you
> don't want to do accept a change to mitigate it because that could
> mean no further discussion on it and no further work toward solving
> it.
>
> But it seems to me a "proper" solution to this will cross a number
> of areas so this isn't just "my" problem and, as you point out, it's
> likely to become increasingly problematic over time.
>
> So what are your ideas and recommendations on how to handle hotplug
> memory at this granularity for this much RAM (and larger amounts)?
First off, this is not my platform, and not my problem, so it's funny
you ask me :)
Anyway, as I have said before, my first guesses would be:
- increase the granularity size of the "memory chunks", reducing
the number of devices you create.
- delay creating the devices until way after booting, or do it
on a totally different path/thread/workqueue/whatever to
prevent delay at booting
And then there's always:
- don't create them at all, only only do so if userspace asks
you to.
You all have the userspace tools/users for this interface and know it
best to know what will work for them. If you don't, then hey, let's
just delete the whole thing and see who screams :)
thanks,
greg k-h
next prev parent reply other threads:[~2020-06-23 6:02 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-17 7:37 [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement Ian Kent
2020-06-17 7:37 ` [PATCH v2 1/6] kernfs: switch kernfs to use an rwsem Ian Kent
2020-06-17 7:37 ` [PATCH v2 2/6] kernfs: move revalidate to be near lookup Ian Kent
2020-06-17 7:37 ` [PATCH v2 3/6] kernfs: improve kernfs path resolution Ian Kent
2020-06-17 7:38 ` [PATCH v2 4/6] kernfs: use revision to identify directory node changes Ian Kent
2020-06-17 7:38 ` [PATCH v2 5/6] kernfs: refactor attr locking Ian Kent
2020-06-17 7:38 ` [PATCH v2 6/6] kernfs: make attr_mutex a local kernfs node lock Ian Kent
2020-06-19 15:38 ` [PATCH v2 0/6] kernfs: proposed locking and concurrency improvement Tejun Heo
2020-06-19 20:41 ` Rick Lindsley
2020-06-19 22:23 ` Tejun Heo
2020-06-20 2:44 ` Rick Lindsley
2020-06-22 17:53 ` Tejun Heo
2020-06-22 21:22 ` Rick Lindsley
2020-06-23 23:13 ` Tejun Heo
2020-06-24 9:04 ` Rick Lindsley
2020-06-24 9:27 ` Greg Kroah-Hartman
2020-06-24 13:19 ` Tejun Heo
2020-06-25 8:15 ` Ian Kent
2020-06-25 9:43 ` Greg Kroah-Hartman
2020-06-26 0:19 ` Ian Kent
2020-06-21 4:55 ` Ian Kent
2020-06-22 17:48 ` Tejun Heo
2020-06-22 18:03 ` Greg Kroah-Hartman
2020-06-22 21:27 ` Rick Lindsley
2020-06-23 5:21 ` Greg Kroah-Hartman
2020-06-23 5:09 ` Ian Kent
2020-06-23 6:02 ` Greg Kroah-Hartman [this message]
2020-06-23 8:01 ` Ian Kent
2020-06-23 8:29 ` Ian Kent
2020-06-23 11:49 ` Greg Kroah-Hartman
2020-06-23 9:33 ` Rick Lindsley
2020-06-23 11:45 ` Greg Kroah-Hartman
2020-06-23 22:55 ` Rick Lindsley
2020-06-23 11:51 ` Ian Kent
2020-06-21 3:21 ` Ian Kent
2020-12-10 16:44 ` Fox Chen
2020-12-11 2:01 ` [PATCH " Ian Kent
2020-12-11 2:17 ` Ian Kent
2020-12-13 3:46 ` Ian Kent
2020-12-14 6:14 ` Fox Chen
2020-12-14 13:30 ` Ian Kent
2020-12-15 8:33 ` Fox Chen
2020-12-15 12:59 ` Ian Kent
2020-12-17 4:46 ` Ian Kent
2020-12-17 8:54 ` Fox Chen
2020-12-17 10:09 ` Ian Kent
2020-12-17 11:09 ` Ian Kent
2020-12-17 11:48 ` Ian Kent
2020-12-17 15:14 ` Tejun Heo
2020-12-18 7:36 ` Ian Kent
2020-12-18 8:01 ` Fox Chen
2020-12-18 11:21 ` Ian Kent
2020-12-18 13:20 ` Fox Chen
2020-12-19 0:53 ` Ian Kent
2020-12-19 7:47 ` Fox Chen
2020-12-22 2:17 ` Ian Kent
2020-12-18 14:59 ` Tejun Heo
2020-12-19 7:08 ` Ian Kent
2020-12-19 16:23 ` Tejun Heo
2020-12-19 23:52 ` Ian Kent
2020-12-20 1:37 ` Ian Kent
2020-12-21 9:28 ` Fox Chen
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