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From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
	kvm@vger.kernel.org, "Stefan Raspl" <raspl@linux.vnet.ibm.com>
Subject: Re: [PATCH] kvm: no need to check return value of debugfs_create functions
Date: Wed, 23 Jan 2019 09:28:08 +0100	[thread overview]
Message-ID: <1dc2d59b-a178-59cc-42bd-4b09289240dc@de.ibm.com> (raw)
In-Reply-To: <d7b38792-e91f-be0c-20cf-99023962f0a9@redhat.com>



On 23.01.2019 00:11, Paolo Bonzini wrote:
> On 22/01/19 21:48, Greg Kroah-Hartman wrote:
>>> This also brings the question: shall we move these counters out of debugfs into something else?
>> If you have code that relies on debugfs, yes, you need to move that out
>> of debugfs because more and more systems are trying to disable it due to
>> the obvious problems with it (i.e. leaking tons of debugging
>> information).
>>
>> debugfs is for DEBUG information, not for "statistics about how my VM is
>> working".  That sounds like something you need to rely on, so debugfs is
>> not the place for it.
> 
> Yes, we know that and tracepoints are already one replacement.  However,
> they are slower that just a lock-free "vcpu->stats.foo_happened++".

Yes, the tracepoints are not a proper replacement for the counters (especially 
the capability to get numbers after-the-fact. So I would really like to keep
both.

> Another idea that Steven Rostedt and I discussed a while ago is some
> kind of "statfs" which would already provide some code, similar to the
> one that KVM uses to accumulate statistics from multiple VMs or multiple
> VCPUs into a single counter.


I think that would make a lot of sense to have a common filesystem to avoid
code duplication bugs.


  reply	other threads:[~2019-01-23  8:28 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-22 15:21 [PATCH] kvm: no need to check return value of debugfs_create functions Greg Kroah-Hartman
2019-01-22 17:21 ` Sean Christopherson
2019-01-22 17:29   ` Sean Christopherson
2019-01-22 18:40     ` Greg Kroah-Hartman
2019-01-22 20:39 ` Christian Borntraeger
2019-01-22 20:48   ` Greg Kroah-Hartman
2019-01-22 23:11     ` Paolo Bonzini
2019-01-23  8:28       ` Christian Borntraeger [this message]
  -- strict thread matches above, loose matches on Subject: below --
2018-05-29 16:22 Greg Kroah-Hartman
2018-05-29 17:06 ` Paolo Bonzini

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