From: Tom Zanussi <zanussi@us.ibm.com>
To: "Perez-Gonzalez, Inaky" <inaky.perez-gonzalez@intel.com>
Cc: "'karim@opersys.com'" <karim@opersys.com>,
"'Martin Hicks'" <mort@wildopensource.com>,
"'Daniel Stekloff'" <dsteklof@us.ibm.com>,
"'Patrick Mochel'" <mochel@osdl.org>,
"'Randy.Dunlap'" <rddunlap@osdl.org>,
"'hpa@zytor.com'" <hpa@zytor.com>,
"'pavel@ucw.cz'" <pavel@ucw.cz>,
"'jes@wildopensource.com'" <jes@wildopensource.com>,
"'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>,
"'wildos@sgi.com'" <wildos@sgi.com>,
"'Tom Zanussi'" <zanussi@us.ibm.com>
Subject: RE: [patch] printk subsystems
Date: Thu, 17 Apr 2003 16:37:25 -0500 [thread overview]
Message-ID: <16031.7829.215702.474821@lepton.softprops.com> (raw)
In-Reply-To: <A46BBDB345A7D5118EC90002A5072C780C2630D5@orsmsx116.jf.intel.com>
Hi,
Perez-Gonzalez, Inaky writes:
> >
> > relayfs is there to solve the data transfer problems for the most
> > demanding of applications. Sending a few messages here and there
> > isn't really a problem. Sending messages/events/what-you-want-to-call-it
> > by the thousand every second, while using as little locking as possible
> > (lockless-logging is implemented in the case of relayfs' buffer handling
> > routines), and providing per-cpu buffering requires a different beast.
>
> Well, you are doing an IRQ lock (relay_lock_channel()), so it is not
> lockless. Or am I missing anything here? Please let me know, I am
> really interested on how to reduce locking in for logging to the
> minimal.
relayfs actually uses 2 mutually-exclusive schemes internally -
'lockless' and 'locking', depending on the availability of a cmpxchg
instruction (lockless needs cmpxchg). If the lockless scheme is being
used, relay_lock_channel() does no locking or irq disabling of any
kind i.e. it's basically a no-op in that case. It's only when the
'locking' scheme is in use that relay_lock_channel() does locking/irq
disabling. Normally the lockless scheme would be in use - the locking
scheme is there mainly as a fallback, so normally relay_lock_channel()
would indeed cause no locking.
--
Regards,
Tom Zanussi <zanussi@us.ibm.com>
IBM Linux Technology Center/RAS
next prev parent reply other threads:[~2003-04-17 21:29 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-17 19:58 [patch] printk subsystems Perez-Gonzalez, Inaky
2003-04-17 20:34 ` Karim Yaghmour
2003-04-17 21:03 ` Perez-Gonzalez, Inaky
2003-04-17 21:37 ` Tom Zanussi [this message]
2003-04-18 7:21 ` Tom Zanussi
2003-04-18 7:42 ` Greg KH
2003-04-21 15:56 ` Karim Yaghmour
-- strict thread matches above, loose matches on Subject: below --
2003-04-24 18:56 Manfred Spraul
2003-04-24 19:10 ` bob
2003-04-23 0:28 Perez-Gonzalez, Inaky
2003-04-22 22:53 Perez-Gonzalez, Inaky
2003-04-23 3:58 ` Tom Zanussi
2003-04-22 19:02 Perez-Gonzalez, Inaky
2003-04-22 19:03 ` H. Peter Anvin
2003-04-22 21:52 ` Tom Zanussi
2003-04-22 18:46 Perez-Gonzalez, Inaky
2003-04-22 23:28 ` Karim Yaghmour
2003-04-22 5:09 Perez-Gonzalez, Inaky
2003-04-24 18:22 ` bob
2003-04-22 4:02 Perez-Gonzalez, Inaky
2003-04-22 5:52 ` Karim Yaghmour
2003-04-22 6:04 ` Tom Zanussi
2003-04-22 3:04 Perez-Gonzalez, Inaky
2003-04-22 6:00 ` Tom Zanussi
2003-04-22 2:49 Perez-Gonzalez, Inaky
2003-04-22 4:34 ` Karim Yaghmour
2003-04-21 18:42 Perez-Gonzalez, Inaky
2003-04-21 18:23 Perez-Gonzalez, Inaky
2003-04-21 18:30 ` H. Peter Anvin
2003-04-08 23:15 Chuck Ebbert
2003-04-07 20:13 Martin Hicks
2003-04-08 18:41 ` Pavel Machek
2003-04-08 20:02 ` Jes Sorensen
2003-04-08 21:02 ` Pavel Machek
2003-04-08 21:10 ` H. Peter Anvin
2003-04-08 21:57 ` Pavel Machek
2003-04-08 22:02 ` Jes Sorensen
2003-04-08 22:05 ` H. Peter Anvin
2003-04-08 22:55 ` Martin Hicks
2003-04-08 23:10 ` Randy.Dunlap
2003-04-14 18:33 ` Patrick Mochel
2003-04-14 22:33 ` Daniel Stekloff
2003-04-16 18:42 ` Patrick Mochel
2003-04-16 12:35 ` Daniel Stekloff
2003-04-16 19:16 ` Martin Hicks
2003-04-16 12:43 ` Daniel Stekloff
2003-04-17 15:56 ` Martin Hicks
2003-04-17 13:58 ` Karim Yaghmour
2003-04-15 13:27 ` Martin Hicks
2003-04-15 14:40 ` Karim Yaghmour
2003-04-08 22:00 ` Jes Sorensen
2003-04-11 19:21 ` Martin Hicks
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