From: Junaid Shahid <junaids@google.com>
To: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Cc: kvm@vger.kernel.org, andreslc@google.com, pfeiner@google.com,
pbonzini@redhat.com
Subject: Re: [PATCH v3 3/8] kvm: x86: mmu: Fast Page Fault path retries
Date: Thu, 15 Dec 2016 15:36:48 -0800 [thread overview]
Message-ID: <10369248.Ox3tqWMzUc@js-desktop.mtv.corp.google.com> (raw)
In-Reply-To: <1948ea57-76c4-dfe1-bdd2-09dbf265747f@linux.intel.com>
On Thursday, December 15, 2016 03:20:19 PM Xiao Guangrong wrote:
> Why not include lockless_walk into the loop, retry 4 times for a invalid sp is expensive.
Yes, we can move the page table walk inside the loop as well. But I’m sorry I don’t fully understand how an invalid sp will lead to retrying 4 times. Could you please elaborate a bit? Wouldn’t we break out of the loop in that case? Or do you mean the case when a huge page is getting broken down or built up?
> I am curious that did you see this retry is really helpful? :)
No, I haven’t done a comparison with and without the retries since it seemed to be a fairly simple optimization. And it may not be straightforward to reliably reproduce the situation where it will help.
Thanks,
Junaid
next prev parent reply other threads:[~2016-12-15 23:36 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-27 2:19 [PATCH 0/4] Lockless Access Tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-10-27 2:19 ` [PATCH 1/4] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications Junaid Shahid
2016-11-02 18:03 ` Paolo Bonzini
2016-11-02 21:40 ` Junaid Shahid
2016-10-27 2:19 ` [PATCH 2/4] kvm: x86: mmu: Rename spte_is_locklessly_modifiable() Junaid Shahid
2016-10-27 2:19 ` [PATCH 3/4] kvm: x86: mmu: Fast Page Fault path retries Junaid Shahid
2016-10-27 2:19 ` [PATCH 4/4] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-11-02 18:01 ` Paolo Bonzini
2016-11-02 21:42 ` Junaid Shahid
2016-11-08 23:00 ` [PATCH v2 0/5] Lockless Access Tracking " Junaid Shahid
2016-11-08 23:00 ` [PATCH v2 1/5] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications Junaid Shahid
2016-11-21 13:06 ` Paolo Bonzini
2016-11-08 23:00 ` [PATCH v2 2/5] kvm: x86: mmu: Rename spte_is_locklessly_modifiable() Junaid Shahid
2016-11-21 13:07 ` Paolo Bonzini
2016-11-08 23:00 ` [PATCH v2 3/5] kvm: x86: mmu: Fast Page Fault path retries Junaid Shahid
2016-11-21 13:13 ` Paolo Bonzini
2016-11-08 23:00 ` [PATCH v2 4/5] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-11-21 14:42 ` Paolo Bonzini
2016-11-24 3:50 ` Junaid Shahid
2016-11-25 9:45 ` Paolo Bonzini
2016-11-29 2:43 ` Junaid Shahid
2016-11-29 8:09 ` Paolo Bonzini
2016-11-30 0:59 ` Junaid Shahid
2016-11-30 11:09 ` Paolo Bonzini
2016-12-01 22:54 ` Junaid Shahid
2016-12-02 8:33 ` Paolo Bonzini
2016-12-05 22:57 ` Junaid Shahid
2016-11-08 23:00 ` [PATCH v2 5/5] kvm: x86: mmu: Update documentation for fast page fault mechanism Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 0/8] Lockless Access Tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 1/8] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications Junaid Shahid
2016-12-15 6:50 ` Xiao Guangrong
2016-12-15 23:06 ` Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 2/8] kvm: x86: mmu: Rename spte_is_locklessly_modifiable() Junaid Shahid
2016-12-15 6:51 ` Xiao Guangrong
2016-12-07 0:46 ` [PATCH v3 3/8] kvm: x86: mmu: Fast Page Fault path retries Junaid Shahid
2016-12-15 7:20 ` Xiao Guangrong
2016-12-15 23:36 ` Junaid Shahid [this message]
2016-12-16 13:13 ` Xiao Guangrong
2016-12-17 0:36 ` Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 4/8] kvm: x86: mmu: Refactor accessed/dirty checks in mmu_spte_update/clear Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 5/8] kvm: x86: mmu: Introduce a no-tracking version of mmu_spte_update Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 6/8] kvm: x86: mmu: Do not use bit 63 for tracking special SPTEs Junaid Shahid
2016-12-07 0:46 ` [PATCH v3 7/8] kvm: x86: mmu: Lockless access tracking for Intel CPUs without EPT A bits Junaid Shahid
2016-12-14 16:28 ` Paolo Bonzini
2016-12-14 22:36 ` Junaid Shahid
2016-12-14 23:35 ` Paolo Bonzini
2016-12-16 13:04 ` Xiao Guangrong
2016-12-16 15:23 ` Paolo Bonzini
2016-12-17 0:01 ` Junaid Shahid
2016-12-21 9:49 ` Xiao Guangrong
2016-12-21 18:00 ` Paolo Bonzini
2016-12-17 2:04 ` Junaid Shahid
2016-12-17 14:19 ` Paolo Bonzini
2016-12-20 3:36 ` Junaid Shahid
2016-12-20 9:01 ` Paolo Bonzini
2016-12-07 0:46 ` [PATCH v3 8/8] kvm: x86: mmu: Update documentation for fast page fault mechanism Junaid Shahid
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