search for: peterz

...general, progresses. Nor does being mentioned in this document mean we think its a particularly good idea; the data dependency barrier required by Alpha being a prime example. Yes we have it, no you're insane to require it when building new hardware. Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org> --- Documentation/memory-barriers.txt | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index a61be39c7b51..98626125f484 100644 --- a/Documentation/memory-barriers.txt ++...

...general, progresses. Nor does being mentioned in this document mean we think its a particularly good idea; the data dependency barrier required by Alpha being a prime example. Yes we have it, no you're insane to require it when building new hardware. Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org> --- Documentation/memory-barriers.txt | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index a61be39c7b51..98626125f484 100644 --- a/Documentation/memory-barriers.txt ++...

...rnbench 1x -0.13 > > kernbench 2x 0.02 > > dbench 1x -1.77 > > dbench 2x -0.63 > > > > [Jeremy: hinted missing TICKET_LOCK_INC for kick] > > [Oleg: Moving slowpath flag to head, ticket_equals idea] > > [PeterZ: Detailed changelog] > > > > Reported-by: Sasha Levin <sasha.levin at oracle.com> > > Suggested-by: Linus Torvalds <torvalds at linux-foundation.org> > > Signed-off-by: Raghavendra K T <raghavendra.kt at linux.vnet.ibm.com> > > Reviewed-by: Oleg Nest...

...rnbench 1x -0.13 > > kernbench 2x 0.02 > > dbench 1x -1.77 > > dbench 2x -0.63 > > > > [Jeremy: hinted missing TICKET_LOCK_INC for kick] > > [Oleg: Moving slowpath flag to head, ticket_equals idea] > > [PeterZ: Detailed changelog] > > > > Reported-by: Sasha Levin <sasha.levin at oracle.com> > > Suggested-by: Linus Torvalds <torvalds at linux-foundation.org> > > Signed-off-by: Raghavendra K T <raghavendra.kt at linux.vnet.ibm.com> > > Reviewed-by: Oleg Nest...

...nel module where such things no longer warn, they blow the box out of the water.  I made a dinky testcase module (attached), and bisected to the real root.... 19d436268dde95389c616bb3819da73f0a8b28a8 is the first bad commit commit 19d436268dde95389c616bb3819da73f0a8b28a8 Author: Peter Zijlstra <peterz at infradead.org> Date: Sat Feb 25 08:56:53 2017 +0100 debug: Add _ONCE() logic to report_bug() Josh suggested moving the _ONCE logic inside the trap handler, using a bit in the bug_entry::flags field, avoiding the need for the extra variable. Sadly this only wor...

On Thu, Jul 23, 2020 at 03:04:13PM -0400, Waiman Long wrote: > On 7/23/20 2:47 PM, peterz at infradead.org wrote: > > On Thu, Jul 23, 2020 at 02:32:36PM -0400, Waiman Long wrote: > > > BTW, do you have any comment on my v2 lock holder cpu info qspinlock patch? > > > I will have to update the patch to fix the reported 0-day test problem, but > > > I want...

* Waiman Long <Waiman.Long at hp.com> wrote: > Because the qspinlock needs to touch a second cacheline; add a pending > bit and allow a single in-word spinner before we punt to the second > cacheline. > > Signed-off-by: Peter Zijlstra <peterz at infradead.org> > Signed-off-by: Waiman Long <Waiman.Long at hp.com> This patch should have a "From: Peter" in it as well, right? Thanks, Ingo

* Waiman Long <Waiman.Long at hp.com> wrote: > Because the qspinlock needs to touch a second cacheline; add a pending > bit and allow a single in-word spinner before we punt to the second > cacheline. > > Signed-off-by: Peter Zijlstra <peterz at infradead.org> > Signed-off-by: Waiman Long <Waiman.Long at hp.com> This patch should have a "From: Peter" in it as well, right? Thanks, Ingo

mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's 2 to 3 times slower than lock; addl that we use on older CPUs. So we really should use the locked variant everywhere, except that intel manual says that clflush is only ordered by mfence, so we can't. Note: some callers of clflush seems to assume sfence will order it, so there could be existing bugs around

mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's 2 to 3 times slower than lock; addl that we use on older CPUs. So we really should use the locked variant everywhere, except that intel manual says that clflush is only ordered by mfence, so we can't. Note: some callers of clflush seems to assume sfence will order it, so there could be existing bugs around

On Thu, Jul 23, 2020 at 02:32:36PM -0400, Waiman Long wrote: > BTW, do you have any comment on my v2 lock holder cpu info qspinlock patch? > I will have to update the patch to fix the reported 0-day test problem, but > I want to collect other feedback before sending out v3. I want to say I hate it all, it adds instructions to a path we spend an aweful lot of time optimizing without

On Thu, Jul 23, 2020 at 02:32:36PM -0400, Waiman Long wrote: > BTW, do you have any comment on my v2 lock holder cpu info qspinlock patch? > I will have to update the patch to fix the reported 0-day test problem, but > I want to collect other feedback before sending out v3. I want to say I hate it all, it adds instructions to a path we spend an aweful lot of time optimizing without

...+ht sandy bridge 8GB 16vcpu guest) benchmark overcommit %improve kernbench 1x -0.13 kernbench 2x 0.02 dbench 1x -1.77 dbench 2x -0.63 [Jeremy: hinted missing TICKET_LOCK_INC for kick] [Oleg: Moving slowpath flag to head, ticket_equals idea] [PeterZ: Detailed changelog] Reported-by: Sasha Levin <sasha.levin at oracle.com> Suggested-by: Linus Torvalds <torvalds at linux-foundation.org> Signed-off-by: Raghavendra K T <raghavendra.kt at linux.vnet.ibm.com> Reviewed-by: Oleg Nesterov <oleg at redhat.com> Acked-by: David Vr...

...+ht sandy bridge 8GB 16vcpu guest) benchmark overcommit %improve kernbench 1x -0.13 kernbench 2x 0.02 dbench 1x -1.77 dbench 2x -0.63 [Jeremy: hinted missing TICKET_LOCK_INC for kick] [Oleg: Moving slowpath flag to head, ticket_equals idea] [PeterZ: Detailed changelog] Reported-by: Sasha Levin <sasha.levin at oracle.com> Suggested-by: Linus Torvalds <torvalds at linux-foundation.org> Signed-off-by: Raghavendra K T <raghavendra.kt at linux.vnet.ibm.com> Reviewed-by: Oleg Nesterov <oleg at redhat.com> Acked-by: David Vr...

> On Oct 4, 2018, at 1:11 AM, Peter Zijlstra <peterz at infradead.org> wrote: > >> On Thu, Oct 04, 2018 at 09:54:45AM +0200, Vitaly Kuznetsov wrote: >> I was hoping to hear this from you :-) If I am to suggest how we can >> move forward I'd propose: >> - Check if pure TSC can be used on SkyLake+ systems (where TSC s...

> On Oct 4, 2018, at 1:11 AM, Peter Zijlstra <peterz at infradead.org> wrote: > >> On Thu, Oct 04, 2018 at 09:54:45AM +0200, Vitaly Kuznetsov wrote: >> I was hoping to hear this from you :-) If I am to suggest how we can >> move forward I'd propose: >> - Check if pure TSC can be used on SkyLake+ systems (where TSC s...

On 04/17/2014 01:23 PM, Konrad Rzeszutek Wilk wrote: > On Thu, Apr 17, 2014 at 11:03:52AM -0400, Waiman Long wrote: >> v8->v9: >> - Integrate PeterZ's version of the queue spinlock patch with some >> modification: >> http://lkml.kernel.org/r/20140310154236.038181843 at infradead.org >> - Break the more complex patches into smaller ones to ease review effort. >> - Fix a racing condition in the PV qspin...

On 04/17/2014 01:23 PM, Konrad Rzeszutek Wilk wrote: > On Thu, Apr 17, 2014 at 11:03:52AM -0400, Waiman Long wrote: >> v8->v9: >> - Integrate PeterZ's version of the queue spinlock patch with some >> modification: >> http://lkml.kernel.org/r/20140310154236.038181843 at infradead.org >> - Break the more complex patches into smaller ones to ease review effort. >> - Fix a racing condition in the PV qspin...

Peter Zijlstra <peterz at infradead.org> wrote: > +========== > +DISCLAIMER > +========== > + > +This document is not a specification; it is intentionally (for the sake of > +brevity) and unintentionally (due to being human) incomplete. This document is > +meant as a guide to using the various me...

Peter Zijlstra <peterz at infradead.org> wrote: > +========== > +DISCLAIMER > +========== > + > +This document is not a specification; it is intentionally (for the sake of > +brevity) and unintentionally (due to being human) incomplete. This document is > +meant as a guide to using the various me...