From: Steffen Klassert <steffen.klassert@secunet.com>
To: Dan Kruchinin <dkruchinin@acm.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Herbert Xu <herbert@gondor.hengli.com.au>
Subject: Re: [PATCH 2/2] pcrypt: sysfs interface
Date: Fri, 2 Jul 2010 13:21:41 +0200 [thread overview]
Message-ID: <20100702112141.GJ10072@secunet.com> (raw)
In-Reply-To: <AANLkTinFqMtdfvbYDIGjQHoWa3dmUuruTvxG-upUU-7S@mail.gmail.com>
On Fri, Jul 02, 2010 at 02:20:15PM +0400, Dan Kruchinin wrote:
> >
> > Yes, I thought about something like this. You can still take the sum
> > over the percpu objects when you output the statistics.
>
> But summation can not be clear without some kind of lock because
> while we're summing another CPU can increase or decrease its percpu statistic
> counters. Then each statistic percpu counter must be modified under lock, right?
>
Yes, the counters must accessed under lock. In the fastpath functions you
hold the appropriate lock anyway. Modifying a local percpu value should
not be too painfull there.
The expensive thing is to access the percpu statistics, but this happens
on demand and is probaply a rare event.
Steffen
next prev parent reply other threads:[~2010-07-02 11:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-29 16:39 [PATCH 2/2] pcrypt: sysfs interface Dan Kruchinin
2010-06-30 12:47 ` Steffen Klassert
[not found] ` <AANLkTimSgp_5LwfvECaAFnW-_UwxwsYVEjKcZTDIHadx@mail.gmail.com>
2010-07-02 9:08 ` Steffen Klassert
2010-07-02 10:20 ` Dan Kruchinin
2010-07-02 11:21 ` Steffen Klassert [this message]
2010-07-05 11:12 ` Steffen Klassert
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