From: Andrew Morton <akpm@osdl.org>
To: paulmck@us.ibm.com
Cc: dada1@cosmosbay.com, dipankar@in.ibm.com, torvalds@osdl.org,
linux-kernel@vger.kernel.org,
viro@parcelfarce.linux.theplanet.co.uk, nickpiggin@yahoo.com.au,
hch@infradead.org
Subject: Re: [patch 2/2] fix file counting
Date: Fri, 27 Jan 2006 15:28:57 -0800 [thread overview]
Message-ID: <20060127152857.32066a69.akpm@osdl.org> (raw)
In-Reply-To: <20060127231420.GA10075@us.ibm.com>
"Paul E. McKenney" <paulmck@us.ibm.com> wrote:
>
> > > I am using a patch that seems sligthly better : It removes the filp_count_lock
> > > as yours but introduces a percpu variable, and a lazy nr_files . (Its value
> > > can be off with a delta of +/- 16*num_possible_cpus()
> >
> > Yes, I think that is better.
>
> I agree that Eric's approach likely improves performance on large systems
> due to decreased cache thrashing. However, the real problem is getting
> both good throughput and good latency in RCU callback processing, given
> Lee Revell's latency testing results. Once we get that in hand, then
> we should consider Eric's approach.
Dipankar's patch risks worsening large-SMP scalability, doesn't it?
Putting an atomic op into the file_free path?
And afaict it fixes up the skew in the nr_files accounting but we're still
exposed to the risk of large amounts of memory getting chewed up due to RCU
latencies?
(And it forgot to initialise the atomic_t)
(And has a couple of suspicious-looking module exports. We don't support
CONFIG_PROC_FS=m).
next prev parent reply other threads:[~2006-01-27 23:27 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-01-26 18:40 [patch 0/2] RCU: fix various latency/oom issues Dipankar Sarma
2006-01-26 18:41 ` [patch 1/2] rcu batch tuning Dipankar Sarma
2006-01-26 18:42 ` [patch 2/2] fix file counting Dipankar Sarma
2006-01-26 20:15 ` Eric Dumazet
2006-01-27 22:54 ` Andrew Morton
2006-01-27 23:14 ` Paul E. McKenney
2006-01-27 23:28 ` Andrew Morton [this message]
2006-01-28 18:42 ` Dipankar Sarma
2006-01-28 18:51 ` Andrew Morton
2006-01-28 19:10 ` Dipankar Sarma
2006-01-30 17:00 ` Dipankar Sarma
2006-01-31 10:33 ` Eric Dumazet
2006-01-31 20:19 ` Dipankar Sarma
2006-01-26 19:33 ` [patch 1/2] rcu batch tuning Paul E. McKenney
2006-01-26 19:42 ` Dipankar Sarma
2006-02-17 15:41 [PATCH 0/2] RCU updates Dipankar Sarma
2006-02-17 15:43 ` [PATCH 1/2] rcu batch tuning Dipankar Sarma
2006-02-17 15:46 ` [PATCH 2/2] fix file counting Dipankar Sarma
2006-02-18 9:04 ` Andrew Morton
2006-02-18 9:25 ` Dipankar Sarma
2006-02-18 9:45 ` Andrew Morton
2006-02-18 10:06 ` Dipankar Sarma
2006-02-18 10:10 ` Andrew Morton
2006-02-18 10:44 ` Dipankar Sarma
2006-02-18 12:14 ` Christoph Hellwig
2006-02-18 12:31 ` Arjan van de Ven
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