Messages in this thread | | | Date | Mon, 7 Feb 2022 12:16:33 -0300 | From | Marcelo Tosatti <> | Subject | Re: [patch v11 05/13] task isolation: sync vmstats on return to userspace |
| |
On Mon, Feb 07, 2022 at 03:57:18PM +0100, Frederic Weisbecker wrote: > On Fri, Feb 04, 2022 at 02:35:42PM -0300, Marcelo Tosatti wrote: > > The logic to disable vmstat worker thread, when entering > > nohz full, does not cover all scenarios. For example, it is possible > > for the following to happen: > > > > 1) enter nohz_full, which calls refresh_cpu_vm_stats, syncing the stats. > > 2) app runs mlock, which increases counters for mlock'ed pages. > > 3) start -RT loop > > > > Since refresh_cpu_vm_stats from nohz_full logic can happen _before_ > > the mlock, vmstat shepherd can restart vmstat worker thread on > > the CPU in question. > > > > To fix this, use the task isolation prctl interface to quiesce > > deferred actions when returning to userspace. > > > > This patch adds hooks to fork and exit code paths. > > > > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> > > > > --- > > v11: fold patch to add task_isol_exit hooks (Frederic) > > Use _TIF_TASK_ISOL bit on thread flags (Frederic) > > > > v6: modify exit_to_user_mode_loop to cover exceptions and interrupts > > v5: no changes > > v4: add oneshot mode support > > > > include/linux/task_isolation.h | 16 ++++++++++++++++ > > include/linux/vmstat.h | 8 ++++++++ > > kernel/entry/common.c | 15 +++++++++++---- > > kernel/task_isolation.c | 21 +++++++++++++++++++++ > > mm/vmstat.c | 21 +++++++++++++++++++++ > > 5 files changed, 77 insertions(+), 4 deletions(-) > > > > Index: linux-2.6/include/linux/task_isolation.h > > =================================================================== > > --- linux-2.6.orig/include/linux/task_isolation.h > > +++ linux-2.6/include/linux/task_isolation.h > > @@ -27,6 +27,13 @@ static inline void task_isol_free(struct > > __task_isol_free(tsk); > > } > > > > +void __task_isol_exit(struct task_struct *tsk); > > +static inline void task_isol_exit(struct task_struct *tsk) > > +{ > > + if (tsk->task_isol_info) > > + __task_isol_exit(tsk); > > +} > > + > > int prctl_task_isol_feat_get(unsigned long arg2, unsigned long arg3, > > unsigned long arg4, unsigned long arg5); > > int prctl_task_isol_cfg_get(unsigned long arg2, unsigned long arg3, > > @@ -40,12 +47,22 @@ int prctl_task_isol_activate_set(unsigne > > > > int __copy_task_isol(struct task_struct *tsk); > > > > +void task_isol_exit_to_user_mode(void); > > + > > #else > > > > +static inline void task_isol_exit_to_user_mode(void) > > +{ > > +} > > + > > static inline void task_isol_free(struct task_struct *tsk) > > { > > } > > > > +static inline void task_isol_exit(struct task_struct *tsk) > > +{ > > +} > > + > > static inline int prctl_task_isol_feat_get(unsigned long arg2, > > unsigned long arg3, > > unsigned long arg4, > > Index: linux-2.6/include/linux/vmstat.h > > =================================================================== > > --- linux-2.6.orig/include/linux/vmstat.h > > +++ linux-2.6/include/linux/vmstat.h > > @@ -21,6 +21,14 @@ int sysctl_vm_numa_stat_handler(struct c > > void *buffer, size_t *length, loff_t *ppos); > > #endif > > > > +#if defined(CONFIG_SMP) && defined(CONFIG_TASK_ISOLATION) > > +void sync_vmstat(void); > > +#else > > +static inline void sync_vmstat(void) > > +{ > > +} > > +#endif > > + > > struct reclaim_stat { > > unsigned nr_dirty; > > unsigned nr_unqueued_dirty; > > Index: linux-2.6/kernel/entry/common.c > > =================================================================== > > --- linux-2.6.orig/kernel/entry/common.c > > +++ linux-2.6/kernel/entry/common.c > > @@ -6,6 +6,7 @@ > > #include <linux/livepatch.h> > > #include <linux/audit.h> > > #include <linux/tick.h> > > +#include <linux/task_isolation.h> > > > > #include "common.h" > > > > @@ -174,6 +175,9 @@ static unsigned long exit_to_user_mode_l > > if (ti_work & _TIF_NOTIFY_RESUME) > > tracehook_notify_resume(regs); > > > > + if (ti_work & _TIF_TASK_ISOL) > > + task_isol_exit_to_user_mode(); > > + > > /* Architecture specific TIF work */ > > arch_exit_to_user_mode_work(regs, ti_work); > > > > Index: linux-2.6/kernel/task_isolation.c > > =================================================================== > > --- linux-2.6.orig/kernel/task_isolation.c > > +++ linux-2.6/kernel/task_isolation.c > > @@ -18,6 +18,12 @@ > > #include <linux/sysfs.h> > > #include <linux/init.h> > > #include <linux/sched/task.h> > > +#include <linux/mm.h> > > +#include <linux/vmstat.h> > > + > > +void __task_isol_exit(struct task_struct *tsk) > > +{ > > +} > > > > void __task_isol_free(struct task_struct *tsk) > > { > > @@ -251,6 +257,9 @@ static int cfg_feat_quiesce_set(unsigned > > task_isol_info->quiesce_mask = i_qctrl->quiesce_mask; > > task_isol_info->oneshot_mask = i_qctrl->quiesce_oneshot_mask; > > task_isol_info->conf_mask |= ISOL_F_QUIESCE; > > + if (task_isol_info->quiesce_mask & ISOL_F_QUIESCE_VMSTATS) > > + set_thread_flag(TIF_TASK_ISOL); > > Should you check if (i->active_mask == ISOL_F_QUIESCE) before setting the > flag? > > > + > > ret = 0; > > > > out_free: > > @@ -303,6 +312,7 @@ int __copy_task_isol(struct task_struct > > new_info->active_mask = info->active_mask; > > > > tsk->task_isol_info = new_info; > > + set_ti_thread_flag(task_thread_info(tsk), TIF_TASK_ISOL); > > Same here?
Yes, should fix that.
Will wait for more comments before resending -v12.
| |