| Message ID | 1600204258-13683-1-git-send-email-vijayb@linux.microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged | expand |
On Tue 15-09-20 14:10:57, Vijay Balakrishna wrote: > When memory is hotplug added or removed the min_free_kbytes must be > recalculated based on what is expected by khugepaged. Currently > after hotplug, min_free_kbytes will be set to a lower default and higher > default set when THP enabled is lost. This leaves the system with small > min_free_kbytes which isn't suitable for systems especially with network > intensive loads. Typical failure symptoms include HW WATCHDOG reset, > soft lockup hang notices, NETDEVICE WATCHDOG timeouts, and OOM process > kills. This changelog still doesn't explain the underlying problem IMO. It sounds it is papering over some other problem. I do agree that the current behavior is non intuitive and surprising. Justifying the change by that inconsistency is likely much better than arguing with soft lockups and OOMs which shouldn't be a result of this inconsistency. > Fixes: f000565adb77 ("thp: set recommended min free kbytes") > > Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com> > Cc: stable@vger.kernel.org > Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> > --- > include/linux/khugepaged.h | 5 +++++ > mm/khugepaged.c | 13 +++++++++++-- > mm/memory_hotplug.c | 3 +++ > 3 files changed, 19 insertions(+), 2 deletions(-) > > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > index bc45ea1efbf7..c941b7377321 100644 > --- a/include/linux/khugepaged.h > +++ b/include/linux/khugepaged.h > @@ -15,6 +15,7 @@ extern int __khugepaged_enter(struct mm_struct *mm); > extern void __khugepaged_exit(struct mm_struct *mm); > extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma, > unsigned long vm_flags); > +extern void khugepaged_min_free_kbytes_update(void); > #ifdef CONFIG_SHMEM > extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr); > #else > @@ -85,6 +86,10 @@ static inline void collapse_pte_mapped_thp(struct mm_struct *mm, > unsigned long addr) > { > } > + > +static inline void khugepaged_min_free_kbytes_update(void) > +{ > +} > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > #endif /* _LINUX_KHUGEPAGED_H */ > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index cfa0dba5fd3b..4f7107476a6f 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -56,6 +56,9 @@ enum scan_result { > #define CREATE_TRACE_POINTS > #include <trace/events/huge_memory.h> > > +static struct task_struct *khugepaged_thread __read_mostly; > +static DEFINE_MUTEX(khugepaged_mutex); > + > /* default scan 8*512 pte (or vmas) every 30 second */ > static unsigned int khugepaged_pages_to_scan __read_mostly; > static unsigned int khugepaged_pages_collapsed; > @@ -2292,8 +2295,6 @@ static void set_recommended_min_free_kbytes(void) > > int start_stop_khugepaged(void) > { > - static struct task_struct *khugepaged_thread __read_mostly; > - static DEFINE_MUTEX(khugepaged_mutex); > int err = 0; > > mutex_lock(&khugepaged_mutex); > @@ -2320,3 +2321,11 @@ int start_stop_khugepaged(void) > mutex_unlock(&khugepaged_mutex); > return err; > } > + > +void khugepaged_min_free_kbytes_update(void) > +{ > + mutex_lock(&khugepaged_mutex); > + if (khugepaged_enabled() && khugepaged_thread) > + set_recommended_min_free_kbytes(); > + mutex_unlock(&khugepaged_mutex); > +} > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index e9d5ab5d3ca0..3e19272c1fad 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -36,6 +36,7 @@ > #include <linux/memblock.h> > #include <linux/compaction.h> > #include <linux/rmap.h> > +#include <linux/khugepaged.h> > > #include <asm/tlbflush.h> > > @@ -857,6 +858,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, > zone_pcp_update(zone); > > init_per_zone_wmark_min(); > + khugepaged_min_free_kbytes_update(); > > kswapd_run(nid); > kcompactd_run(nid); > @@ -1600,6 +1602,7 @@ static int __ref __offline_pages(unsigned long start_pfn, > pgdat_resize_unlock(zone->zone_pgdat, &flags); > > init_per_zone_wmark_min(); > + khugepaged_min_free_kbytes_update(); > > if (!populated_zone(zone)) { > zone_pcp_reset(zone); > -- > 2.28.0
diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h index bc45ea1efbf7..c941b7377321 100644 --- a/include/linux/khugepaged.h +++ b/include/linux/khugepaged.h @@ -15,6 +15,7 @@ extern int __khugepaged_enter(struct mm_struct *mm); extern void __khugepaged_exit(struct mm_struct *mm); extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma, unsigned long vm_flags); +extern void khugepaged_min_free_kbytes_update(void); #ifdef CONFIG_SHMEM extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr); #else @@ -85,6 +86,10 @@ static inline void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) { } + +static inline void khugepaged_min_free_kbytes_update(void) +{ +} #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif /* _LINUX_KHUGEPAGED_H */ diff --git a/mm/khugepaged.c b/mm/khugepaged.c index cfa0dba5fd3b..4f7107476a6f 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -56,6 +56,9 @@ enum scan_result { #define CREATE_TRACE_POINTS #include <trace/events/huge_memory.h> +static struct task_struct *khugepaged_thread __read_mostly; +static DEFINE_MUTEX(khugepaged_mutex); + /* default scan 8*512 pte (or vmas) every 30 second */ static unsigned int khugepaged_pages_to_scan __read_mostly; static unsigned int khugepaged_pages_collapsed; @@ -2292,8 +2295,6 @@ static void set_recommended_min_free_kbytes(void) int start_stop_khugepaged(void) { - static struct task_struct *khugepaged_thread __read_mostly; - static DEFINE_MUTEX(khugepaged_mutex); int err = 0; mutex_lock(&khugepaged_mutex); @@ -2320,3 +2321,11 @@ int start_stop_khugepaged(void) mutex_unlock(&khugepaged_mutex); return err; } + +void khugepaged_min_free_kbytes_update(void) +{ + mutex_lock(&khugepaged_mutex); + if (khugepaged_enabled() && khugepaged_thread) + set_recommended_min_free_kbytes(); + mutex_unlock(&khugepaged_mutex); +} diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index e9d5ab5d3ca0..3e19272c1fad 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -36,6 +36,7 @@ #include <linux/memblock.h> #include <linux/compaction.h> #include <linux/rmap.h> +#include <linux/khugepaged.h> #include <asm/tlbflush.h> @@ -857,6 +858,7 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages, zone_pcp_update(zone); init_per_zone_wmark_min(); + khugepaged_min_free_kbytes_update(); kswapd_run(nid); kcompactd_run(nid); @@ -1600,6 +1602,7 @@ static int __ref __offline_pages(unsigned long start_pfn, pgdat_resize_unlock(zone->zone_pgdat, &flags); init_per_zone_wmark_min(); + khugepaged_min_free_kbytes_update(); if (!populated_zone(zone)) { zone_pcp_reset(zone);
When memory is hotplug added or removed the min_free_kbytes must be recalculated based on what is expected by khugepaged. Currently after hotplug, min_free_kbytes will be set to a lower default and higher default set when THP enabled is lost. This leaves the system with small min_free_kbytes which isn't suitable for systems especially with network intensive loads. Typical failure symptoms include HW WATCHDOG reset, soft lockup hang notices, NETDEVICE WATCHDOG timeouts, and OOM process kills. Fixes: f000565adb77 ("thp: set recommended min free kbytes") Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com> Cc: stable@vger.kernel.org Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com> --- include/linux/khugepaged.h | 5 +++++ mm/khugepaged.c | 13 +++++++++++-- mm/memory_hotplug.c | 3 +++ 3 files changed, 19 insertions(+), 2 deletions(-)