On Fri, Jun 15, 2018 at 12:15 AM Jin, Yao wrote:
>
>
>
> On 6/15/2018 1:59 PM, Stephane Eranian wrote:
> > On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
> >>
> >> When doing sampling, for example:
> >>
> >> perf record -e cycles:u ...
> >>
> >> On workloads that do a lot of kernel entry/exits we
On Tue, Jun 19, 2018 at 09:39:02AM +0800, Jin, Yao wrote:
>
>
> On 6/18/2018 6:45 PM, Peter Zijlstra wrote:
> > On Mon, Jun 18, 2018 at 02:55:32PM +0800, Jin, Yao wrote:
> > > Thanks for providing the patch. I understand this approach.
> > >
> > > In my opinion, the skid window is from counter o
On 6/18/2018 6:45 PM, Peter Zijlstra wrote:
On Mon, Jun 18, 2018 at 02:55:32PM +0800, Jin, Yao wrote:
Thanks for providing the patch. I understand this approach.
In my opinion, the skid window is from counter overflow to interrupt
delivered. While if the skid window is too *big* (e.g. user -
On Sat, Jun 16, 2018 at 10:27:27AM +0900, Linus Torvalds wrote:
> On Fri, Jun 15, 2018 at 8:36 PM Mark Rutland wrote:
> >
> > At least for sampling the GPRs, we could do something like below
> > unconditionally, which seems sufficient for my test cases.
>
> Ack.
>
> The PEBS case may need checki
On Mon, Jun 18, 2018 at 02:55:32PM +0800, Jin, Yao wrote:
> Thanks for providing the patch. I understand this approach.
>
> In my opinion, the skid window is from counter overflow to interrupt
> delivered. While if the skid window is too *big* (e.g. user -> kernel), it
> should be not very useful.
On Fri, Jun 15, 2018 at 01:31:34PM +, Liang, Kan wrote:
> > On Thu, Jun 14, 2018 at 11:02:53PM -0700, Stephane Eranian wrote:
> > > On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
> > > > + /*
> > > > +* Due to interrupt latency (AKA "skid"), we may enter the
> > > > +* ke
On 6/15/2018 7:36 PM, Mark Rutland wrote:
On Fri, Jun 15, 2018 at 06:03:22PM +0800, Jin Yao wrote:
When doing sampling, for example:
perf record -e cycles:u ...
On workloads that do a lot of kernel entry/exits we see kernel
samples, even though :u is specified. This is due to skid existing.
On Fri, Jun 15, 2018 at 8:36 PM Mark Rutland wrote:
>
> At least for sampling the GPRs, we could do something like below
> unconditionally, which seems sufficient for my test cases.
Ack.
The PEBS case may need checking, but maybe PEBS doesn't even have this issue?
Linus
> On Thu, Jun 14, 2018 at 11:02:53PM -0700, Stephane Eranian wrote:
> > On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
> > > + /*
> > > +* Due to interrupt latency (AKA "skid"), we may enter the
> > > +* kernel before taking an overflow, even if the PMU is only
> > > +
On Fri, Jun 15, 2018 at 06:03:22PM +0800, Jin Yao wrote:
> When doing sampling, for example:
>
> perf record -e cycles:u ...
>
> On workloads that do a lot of kernel entry/exits we see kernel
> samples, even though :u is specified. This is due to skid existing.
>
> This might be a security issue
On Thu, Jun 14, 2018 at 11:02:53PM -0700, Stephane Eranian wrote:
> On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
> > + /*
> > +* Due to interrupt latency (AKA "skid"), we may enter the
> > +* kernel before taking an overflow, even if the PMU is only
> > +* counting
On 6/15/2018 1:59 PM, Stephane Eranian wrote:
On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
When doing sampling, for example:
perf record -e cycles:u ...
On workloads that do a lot of kernel entry/exits we see kernel
samples, even though :u is specified. This is due to skid existing.
Th
On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
>
> When doing sampling, for example:
>
> perf record -e cycles:u ...
>
> On workloads that do a lot of kernel entry/exits we see kernel
> samples, even though :u is specified. This is due to skid existing.
>
> This might be a security issue because i
On Thu, Jun 14, 2018 at 7:10 PM Jin Yao wrote:
>
> When doing sampling, for example:
>
> perf record -e cycles:u ...
>
> On workloads that do a lot of kernel entry/exits we see kernel
> samples, even though :u is specified. This is due to skid existing.
>
> This might be a security issue because i
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