linux-kernel - Re: devpts mounts too slowly

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Message-Id: <20090609165304.add1a872.akpm@linux-foundation.org>
Date:	Tue, 9 Jun 2009 16:53:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ray Lee <ray-lk@...rabbit.org>
Cc:	hpa@...or.com, renton@...ton.name, linux-kernel@...r.kernel.org
Subject: Re: devpts mounts too slowly

On Tue, 9 Jun 2009 16:30:31 -0700
Ray Lee <ray-lk@...rabbit.org> wrote:

> On Tue, Jun 9, 2009 at 4:19 PM, Andrew Morton<akpm@...ux-foundation.org> wrote:
> > On Wed, 03 Jun 2009 14:28:56 -0700
> > "H. Peter Anvin" <hpa@...or.com> wrote:
> >
> >> Alexey Vlasov wrote:
> >> > Hi.
> >> >
> >> > In comparison with bind/proc mounting it takes a lot more time mounting
> >> > devpts. Is it possible to somehow accelerate the process? Now there are
> >> > about 5k devpts mounting, it already took 20 minutes, further will take
> >> > even more time.
> >> >
> >> > # time mount -n -i -t devpts none /home/staff/.server-1/dev/pts
> >> > real __ __0m0.295s
> >> > user __ __0m0.000s
> >> > sys __ __ 0m0.288s
> >> >
> >>
> >> A profile would be handy here. __There is no sensible reason for this to
> >> that 0.3 seconds. __This might be RCU-epoch related?
> >>
> >
> > It seems OK here.
> >
> > akpm2:/home/akpm/xx# time mount -n -i -t devpts none /tmp/pts
> > mount -n -i -t devpts none /tmp/pts __0.00s user 0.00s system 0% cpu 0.002 total
> 
> I read the Original Post as that test being performed with 5k /dev/pts
> already mounted.

hm, OK.

I've now mounted 15000 devpts's and still no slowdown is evident.
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