From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: ehrhardt@linux.vnet.ibm.com, kvm@vger.kernel.org,
Carsten Otte <cotte@de.ibm.com>
Subject: Re: [PATCH 2/6] kvm-s390: use hrtimer for clock wakeup from idle
Date: Thu, 7 May 2009 12:34:58 +0200 [thread overview]
Message-ID: <200905071234.58511.borntraeger@de.ibm.com> (raw)
In-Reply-To: <4A02B5B4.6050701@redhat.com>
Am Thursday 07 May 2009 12:19:32 schrieb Avi Kivity:
> Makes sense.
>
> Back when irqsave/irqrestore were expensive on x86 (P4 days, I think it
> was ~100 cycles) there was talk of using a software irq disable flag
> instead of using the hardware support. So
>
> - local_irq_disable() sets a flag
>
> - interrupt handlers check the flag, if set they schedule the interrupt
> handler and return immediately
>
> - local_irq_restore() clears the flag and fires and scheduled handlers
>
> Now these operations are pretty cheap on x86, but maybe that can apply
> to s390.
Interesting idea. Nevertheless, I dont think it improve our situation. The affected instructions (stosm and stnsm) are more expensive than compare and swap, but its nowhere near the ~100 cycles of P4.
Christian
next prev parent reply other threads:[~2009-05-07 10:35 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-05 14:39 [PATCH 0/6] kvm-s390: collection of kvm-s390 fixes ehrhardt
2009-05-05 14:39 ` [PATCH 1/6] kvm-s390: Fix memory slot versus run ehrhardt
2009-05-06 12:01 ` Avi Kivity
2009-05-11 13:00 ` Christian Ehrhardt
2009-05-11 13:15 ` Avi Kivity
2009-05-11 13:46 ` Christian Ehrhardt
2009-05-11 14:02 ` Avi Kivity
2009-05-11 14:42 ` Christian Ehrhardt
2009-05-11 15:01 ` Avi Kivity
2009-05-12 9:15 ` Christian Ehrhardt
2009-05-12 11:35 ` Avi Kivity
2009-05-12 13:33 ` Christian Ehrhardt
2009-05-17 22:31 ` Avi Kivity
2009-05-20 12:05 ` Christian Ehrhardt
2009-05-05 14:39 ` [PATCH 2/6] kvm-s390: use hrtimer for clock wakeup from idle ehrhardt
2009-05-06 12:10 ` Avi Kivity
2009-05-06 12:36 ` Christian Borntraeger
2009-05-07 10:19 ` Avi Kivity
2009-05-07 10:34 ` Christian Borntraeger [this message]
2009-05-20 15:48 ` Hollis Blanchard
2009-05-05 14:39 ` [PATCH 3/6] kvm-s390: optimize float int lock: spin_lock_bh --> spin_lock ehrhardt
2009-05-05 14:39 ` [PATCH 4/6] kvm-s390: Unlink vcpu on destroy ehrhardt
2009-05-06 12:11 ` Avi Kivity
2009-05-11 13:00 ` Christian Ehrhardt
2009-05-05 14:39 ` [PATCH 5/6] kvm-s390: Sanity check on validity intercept ehrhardt
2009-05-05 14:39 ` [PATCH 6/6] kvm-s390: Verify memory in kvm run ehrhardt
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=200905071234.58511.borntraeger@de.ibm.com \
--to=borntraeger@de.ibm.com \
--cc=avi@redhat.com \
--cc=cotte@de.ibm.com \
--cc=ehrhardt@linux.vnet.ibm.com \
--cc=kvm@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.