From: Scott Wood <scottwood@freescale•com>
To: Kevin Hao <haokexin@gmail•com>
Cc: linuxppc <linuxppc-dev@lists•ozlabs.org>
Subject: Re: [PATCH 1/4] powerpc/book3e: introduce external_input_edge exception handler for 64bit kernel
Date: Wed, 15 May 2013 16:30:26 -0500 [thread overview]
Message-ID: <1368653426.8202.34@snotra> (raw)
In-Reply-To: <20130514020317.GB21564@pek-khao-d1.corp.ad.wrs.com> (from haokexin@gmail.com on Mon May 13 21:03:17 2013)
On 05/13/2013 09:03:17 PM, Kevin Hao wrote:
> On Mon, May 13, 2013 at 10:47:17AM -0500, Scott Wood wrote:
> > On 05/11/2013 06:26:21 PM, Kevin Hao wrote:
> > >In the external proxy facility mode, the interrupt is automatically
> > >acknowledged with the same effect as reading the IACK register. So
> > >this makes external input interrupt more like edge sensitive. That
> > >means we can leave the irq hard enabled when it occurs with irq =20
> soft
> > >disabled just like the dec and doorbell interrupt. But the External
> > >Proxy Register(EPR) is only considered valid from the time that the
> > >external interrupt occurs until MSR[EE] is set to 1. So we have to
> > >save the EPR before irq hard enabled.
> >
> > Is it really worth it?
>=20
> Maybe. :-)
> Compare with the current kernel:
> * The overhead is that we need additional load & store the contents =20
> of
> the EPR from/to PACA.
There's also mental overhead of the extra complexity. The lazy EE =20
stuff is already fiddly enough (e.g. the recent KVM patches).
> * The bonus is we keep the irq hard enabled when a external =20
> interrupt occurs
> with irq soft-disabled. As I know we should leave the irq hard =20
> enabled as
> much as possible. This is also the primary reason that we =20
> introduce the
> Lazy EE.
I don't think "as much as possible" is a good way to look at it, so =20
much as "as much as is practical", balanced by also wanting to keep the =20
code as simple as is practical.
-Scott=
next prev parent reply other threads:[~2013-05-15 21:30 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-11 23:26 [PATCH 0/4] enable the PACA_IRQ_EE_EDGE support for book3e Kevin Hao
2013-05-11 23:26 ` [PATCH 1/4] powerpc/book3e: introduce external_input_edge exception handler for 64bit kernel Kevin Hao
2013-05-13 15:47 ` Scott Wood
2013-05-14 2:03 ` Kevin Hao
2013-05-15 21:30 ` Scott Wood [this message]
2013-05-16 8:43 ` Kevin Hao
2013-05-11 23:26 ` [PATCH 2/4] powerpc: move the patch_exception to a common place Kevin Hao
2013-05-11 23:26 ` [PATCH 3/4] powerpc: use patch_exception to update the debug exception handler Kevin Hao
2013-05-11 23:26 ` [PATCH 4/4] powerpc/fsl-book3e: enable the external_input_edge " Kevin Hao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1368653426.8202.34@snotra \
--to=scottwood@freescale$(echo .)com \
--cc=haokexin@gmail$(echo .)com \
--cc=linuxppc-dev@lists$(echo .)ozlabs.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox