Re: [tip:locking/core] sched/cputime: Fix invalid gtime in proc
* Frederic Weisbecker wrote: > On Fri, Dec 04, 2015 at 03:53:13AM -0800, tip-bot for Hiroshi Shimamoto wrote: > > Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b > > Gitweb: > > http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b > > Author: Hiroshi Shimamoto > > AuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 > > Committer: Ingo Molnar > > CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 > > > > sched/cputime: Fix invalid gtime in proc > > > > /proc/stats shows invalid gtime when the thread is running in guest. > > When vtime accounting is not enabled, we cannot get a valid delta. > > The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap > > is only updated when vtime accounting is runtime enabled. > > > > This patch makes task_gtime() just return gtime without computing the > > buggy non-existing tickless delta when vtime accounting is not enabled. > > > > Use context_tracking_is_enabled() to check if vtime is accounting on > > some cpu, in which case only we need to check the tickless delta. This > > way we fix the gtime value regression on machines not running nohz full. > > > > The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and > > CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. > > > > I ran and stop a busy loop in VM and see the gtime in host. > > Dump the 43rd field which shows the gtime in every second: > > > > # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep > > 1; done > > S 4348 > > R 7064566 > > R 7064766 > > R 7064967 > > R 7065168 > > S 4759 > > S 4759 > > > > During running busy loop, it returns large value. > > > > After applying this patch, we can see right gtime. > > > > # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; > > sleep 1; done > > S 5338 > > R 5365 > > R 5465 > > R 5566 > > R 5666 > > S 5726 > > S 5726 > > > > Signed-off-by: Hiroshi Shimamoto > > Signed-off-by: Frederic Weisbecker > > Signed-off-by: Peter Zijlstra (Intel) > > Cc: Chris Metcalf > > Cc: Christoph Lameter > > Cc: Linus Torvalds > > Cc: Luiz Capitulino > > Cc: Mike Galbraith > > Cc: Paul E . McKenney > > Cc: Paul E. McKenney > > Cc: Peter Zijlstra > > Cc: Rik van Riel > > Cc: Thomas Gleixner > > Link: > > http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweis...@gmail.com > > Signed-off-by: Ingo Molnar > > --- > > Thanks for applying the patchset! > > However we may want to backport this one, it's a regression fix affecting > CONFIG_NO_HZ_FULL=y with nohz_full off (99% of many distros defaults). > > Thanks. Absolutely, not sure why I forgot that tag - I added it for other recent fixes. Greg, please consider applying this upstream fix to -stable as well: 2541117b0cf7 ("sched/cputime: Fix invalid gtime in proc") Note, the commit will cherry-pick cleanly all the way back to v3.9 (released 2.5+ years ago), but it will only build on v3.14 and later kernels. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:locking/core] sched/cputime: Fix invalid gtime in proc
On Fri, Dec 04, 2015 at 03:53:13AM -0800, tip-bot for Hiroshi Shimamoto wrote: > Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b > Gitweb: http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b > Author: Hiroshi Shimamoto > AuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 > Committer: Ingo Molnar > CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 > > sched/cputime: Fix invalid gtime in proc > > /proc/stats shows invalid gtime when the thread is running in guest. > When vtime accounting is not enabled, we cannot get a valid delta. > The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap > is only updated when vtime accounting is runtime enabled. > > This patch makes task_gtime() just return gtime without computing the > buggy non-existing tickless delta when vtime accounting is not enabled. > > Use context_tracking_is_enabled() to check if vtime is accounting on > some cpu, in which case only we need to check the tickless delta. This > way we fix the gtime value regression on machines not running nohz full. > > The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and > CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. > > I ran and stop a busy loop in VM and see the gtime in host. > Dump the 43rd field which shows the gtime in every second: > ># while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep > 1; done > S 4348 > R 7064566 > R 7064766 > R 7064967 > R 7065168 > S 4759 > S 4759 > > During running busy loop, it returns large value. > > After applying this patch, we can see right gtime. > ># while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; > sleep 1; done > S 5338 > R 5365 > R 5465 > R 5566 > R 5666 > S 5726 > S 5726 > > Signed-off-by: Hiroshi Shimamoto > Signed-off-by: Frederic Weisbecker > Signed-off-by: Peter Zijlstra (Intel) > Cc: Chris Metcalf > Cc: Christoph Lameter > Cc: Linus Torvalds > Cc: Luiz Capitulino > Cc: Mike Galbraith > Cc: Paul E . McKenney > Cc: Paul E. McKenney > Cc: Peter Zijlstra > Cc: Rik van Riel > Cc: Thomas Gleixner > Link: > http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweis...@gmail.com > Signed-off-by: Ingo Molnar > --- Thanks for applying the patchset! However we may want to backport this one, it's a regression fix affecting CONFIG_NO_HZ_FULL=y with nohz_full off (99% of many distros defaults). Thanks. > kernel/sched/cputime.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c > index 26a5446..05de80b 100644 > --- a/kernel/sched/cputime.c > +++ b/kernel/sched/cputime.c > @@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t) > unsigned int seq; > cputime_t gtime; > > + if (!context_tracking_is_enabled()) > + return t->gtime; > + > do { > seq = read_seqbegin(>vtime_seqlock); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:locking/core] sched/cputime: Fix invalid gtime in proc
On Fri, Dec 04, 2015 at 03:53:13AM -0800, tip-bot for Hiroshi Shimamoto wrote: > Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b > Gitweb: http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b > Author: Hiroshi Shimamoto> AuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 > Committer: Ingo Molnar > CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 > > sched/cputime: Fix invalid gtime in proc > > /proc/stats shows invalid gtime when the thread is running in guest. > When vtime accounting is not enabled, we cannot get a valid delta. > The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap > is only updated when vtime accounting is runtime enabled. > > This patch makes task_gtime() just return gtime without computing the > buggy non-existing tickless delta when vtime accounting is not enabled. > > Use context_tracking_is_enabled() to check if vtime is accounting on > some cpu, in which case only we need to check the tickless delta. This > way we fix the gtime value regression on machines not running nohz full. > > The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and > CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. > > I ran and stop a busy loop in VM and see the gtime in host. > Dump the 43rd field which shows the gtime in every second: > ># while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep > 1; done > S 4348 > R 7064566 > R 7064766 > R 7064967 > R 7065168 > S 4759 > S 4759 > > During running busy loop, it returns large value. > > After applying this patch, we can see right gtime. > ># while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; > sleep 1; done > S 5338 > R 5365 > R 5465 > R 5566 > R 5666 > S 5726 > S 5726 > > Signed-off-by: Hiroshi Shimamoto > Signed-off-by: Frederic Weisbecker > Signed-off-by: Peter Zijlstra (Intel) > Cc: Chris Metcalf > Cc: Christoph Lameter > Cc: Linus Torvalds > Cc: Luiz Capitulino > Cc: Mike Galbraith > Cc: Paul E . McKenney > Cc: Paul E. McKenney > Cc: Peter Zijlstra > Cc: Rik van Riel > Cc: Thomas Gleixner > Link: > http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweis...@gmail.com > Signed-off-by: Ingo Molnar > --- Thanks for applying the patchset! However we may want to backport this one, it's a regression fix affecting CONFIG_NO_HZ_FULL=y with nohz_full off (99% of many distros defaults). Thanks. > kernel/sched/cputime.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c > index 26a5446..05de80b 100644 > --- a/kernel/sched/cputime.c > +++ b/kernel/sched/cputime.c > @@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t) > unsigned int seq; > cputime_t gtime; > > + if (!context_tracking_is_enabled()) > + return t->gtime; > + > do { > seq = read_seqbegin(>vtime_seqlock); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [tip:locking/core] sched/cputime: Fix invalid gtime in proc
* Frederic Weisbeckerwrote: > On Fri, Dec 04, 2015 at 03:53:13AM -0800, tip-bot for Hiroshi Shimamoto wrote: > > Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b > > Gitweb: > > http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b > > Author: Hiroshi Shimamoto > > AuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 > > Committer: Ingo Molnar > > CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 > > > > sched/cputime: Fix invalid gtime in proc > > > > /proc/stats shows invalid gtime when the thread is running in guest. > > When vtime accounting is not enabled, we cannot get a valid delta. > > The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap > > is only updated when vtime accounting is runtime enabled. > > > > This patch makes task_gtime() just return gtime without computing the > > buggy non-existing tickless delta when vtime accounting is not enabled. > > > > Use context_tracking_is_enabled() to check if vtime is accounting on > > some cpu, in which case only we need to check the tickless delta. This > > way we fix the gtime value regression on machines not running nohz full. > > > > The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and > > CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. > > > > I ran and stop a busy loop in VM and see the gtime in host. > > Dump the 43rd field which shows the gtime in every second: > > > > # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep > > 1; done > > S 4348 > > R 7064566 > > R 7064766 > > R 7064967 > > R 7065168 > > S 4759 > > S 4759 > > > > During running busy loop, it returns large value. > > > > After applying this patch, we can see right gtime. > > > > # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; > > sleep 1; done > > S 5338 > > R 5365 > > R 5465 > > R 5566 > > R 5666 > > S 5726 > > S 5726 > > > > Signed-off-by: Hiroshi Shimamoto > > Signed-off-by: Frederic Weisbecker > > Signed-off-by: Peter Zijlstra (Intel) > > Cc: Chris Metcalf > > Cc: Christoph Lameter > > Cc: Linus Torvalds > > Cc: Luiz Capitulino > > Cc: Mike Galbraith > > Cc: Paul E . McKenney > > Cc: Paul E. McKenney > > Cc: Peter Zijlstra > > Cc: Rik van Riel > > Cc: Thomas Gleixner > > Link: > > http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweis...@gmail.com > > Signed-off-by: Ingo Molnar > > --- > > Thanks for applying the patchset! > > However we may want to backport this one, it's a regression fix affecting > CONFIG_NO_HZ_FULL=y with nohz_full off (99% of many distros defaults). > > Thanks. Absolutely, not sure why I forgot that tag - I added it for other recent fixes. Greg, please consider applying this upstream fix to -stable as well: 2541117b0cf7 ("sched/cputime: Fix invalid gtime in proc") Note, the commit will cherry-pick cleanly all the way back to v3.9 (released 2.5+ years ago), but it will only build on v3.14 and later kernels. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[tip:locking/core] sched/cputime: Fix invalid gtime in proc
Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b Gitweb: http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b Author: Hiroshi Shimamoto AuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 Committer: Ingo Molnar CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 sched/cputime: Fix invalid gtime in proc /proc/stats shows invalid gtime when the thread is running in guest. When vtime accounting is not enabled, we cannot get a valid delta. The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap is only updated when vtime accounting is runtime enabled. This patch makes task_gtime() just return gtime without computing the buggy non-existing tickless delta when vtime accounting is not enabled. Use context_tracking_is_enabled() to check if vtime is accounting on some cpu, in which case only we need to check the tickless delta. This way we fix the gtime value regression on machines not running nohz full. The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. I ran and stop a busy loop in VM and see the gtime in host. Dump the 43rd field which shows the gtime in every second: # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done S 4348 R 7064566 R 7064766 R 7064967 R 7065168 S 4759 S 4759 During running busy loop, it returns large value. After applying this patch, we can see right gtime. # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done S 5338 R 5365 R 5465 R 5566 R 5666 S 5726 S 5726 Signed-off-by: Hiroshi Shimamoto Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Chris Metcalf Cc: Christoph Lameter Cc: Linus Torvalds Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweis...@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/cputime.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 26a5446..05de80b 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t) unsigned int seq; cputime_t gtime; + if (!context_tracking_is_enabled()) + return t->gtime; + do { seq = read_seqbegin(>vtime_seqlock); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[tip:locking/core] sched/cputime: Fix invalid gtime in proc
Commit-ID: 2541117b0cf79977fa11a0d6e17d61010677bd7b Gitweb: http://git.kernel.org/tip/2541117b0cf79977fa11a0d6e17d61010677bd7b Author: Hiroshi ShimamotoAuthorDate: Thu, 19 Nov 2015 16:47:28 +0100 Committer: Ingo Molnar CommitDate: Fri, 4 Dec 2015 10:18:49 +0100 sched/cputime: Fix invalid gtime in proc /proc/stats shows invalid gtime when the thread is running in guest. When vtime accounting is not enabled, we cannot get a valid delta. The delta is calculated with now - tsk->vtime_snap, but tsk->vtime_snap is only updated when vtime accounting is runtime enabled. This patch makes task_gtime() just return gtime without computing the buggy non-existing tickless delta when vtime accounting is not enabled. Use context_tracking_is_enabled() to check if vtime is accounting on some cpu, in which case only we need to check the tickless delta. This way we fix the gtime value regression on machines not running nohz full. The kernel config contains CONFIG_VIRT_CPU_ACCOUNTING_GEN=y and CONFIG_NO_HZ_FULL_ALL=n and boot without nohz_full. I ran and stop a busy loop in VM and see the gtime in host. Dump the 43rd field which shows the gtime in every second: # while :; do awk '{print $3" "$43}' /proc/3955/task/4014/stat; sleep 1; done S 4348 R 7064566 R 7064766 R 7064967 R 7065168 S 4759 S 4759 During running busy loop, it returns large value. After applying this patch, we can see right gtime. # while :; do awk '{print $3" "$43}' /proc/10913/task/10956/stat; sleep 1; done S 5338 R 5365 R 5465 R 5566 R 5666 S 5726 S 5726 Signed-off-by: Hiroshi Shimamoto Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Chris Metcalf Cc: Christoph Lameter Cc: Linus Torvalds Cc: Luiz Capitulino Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1447948054-28668-2-git-send-email-fweis...@gmail.com Signed-off-by: Ingo Molnar --- kernel/sched/cputime.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 26a5446..05de80b 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t) unsigned int seq; cputime_t gtime; + if (!context_tracking_is_enabled()) + return t->gtime; + do { seq = read_seqbegin(>vtime_seqlock); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/