On Tue 15-09-20 17:09:48, Andrew Morton wrote: > From: Vijay Balakrishna <vijayb@xxxxxxxxxxxxxxxxxxx> > Subject: mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged > > 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. > > Link: https://lkml.kernel.org/r/1600204258-13683-1-git-send-email-vijayb@xxxxxxxxxxxxxxxxxxx > Fixes: f000565adb77 ("thp: set recommended min free kbytes") > Signed-off-by: Vijay Balakrishna <vijayb@xxxxxxxxxxxxxxxxxxx> > Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > Cc: Allen Pais <apais@xxxxxxxxxxxxx> > Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxx> > Cc: Oleg Nesterov <oleg@xxxxxxxxxx> > Cc: Song Liu <songliubraving@xxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> The patch has been explicitly nacked by Kirill IIRC. I am also not happy about it because the changelog doesn't really explain the problem and the follow up discussion didn't drill down to the underlying problem either. Maybe we want to make the min_free_kbytes udpate consistent with the boot but the current changelog is incomplete and this shouldn't have been added yet. > --- > > include/linux/khugepaged.h | 5 +++++ > mm/khugepaged.c | 13 +++++++++++-- > mm/memory_hotplug.c | 3 +++ > 3 files changed, 19 insertions(+), 2 deletions(-) > > --- a/include/linux/khugepaged.h~mm-khugepaged-recalculate-min_free_kbytes-after-memory-hotplug-as-expected-by-khugepaged > +++ a/include/linux/khugepaged.h > @@ -15,6 +15,7 @@ extern int __khugepaged_enter(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_t > unsigned long addr) > { > } > + > +static inline void khugepaged_min_free_kbytes_update(void) > +{ > +} > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > > #endif /* _LINUX_KHUGEPAGED_H */ > --- a/mm/khugepaged.c~mm-khugepaged-recalculate-min_free_kbytes-after-memory-hotplug-as-expected-by-khugepaged > +++ a/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_kby > > 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 @@ fail: > 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); > +} > --- a/mm/memory_hotplug.c~mm-khugepaged-recalculate-min_free_kbytes-after-memory-hotplug-as-expected-by-khugepaged > +++ a/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 > zone_pcp_update(zone); > > init_per_zone_wmark_min(); > + khugepaged_min_free_kbytes_update(); > > kswapd_run(nid); > kcompactd_run(nid); > @@ -1614,6 +1616,7 @@ static int __ref __offline_pages(unsigne > 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); > _ > > Patches currently in -mm which might be from vijayb@xxxxxxxxxxxxxxxxxxx are > > mm-khugepaged-recalculate-min_free_kbytes-after-memory-hotplug-as-expected-by-khugepaged.patch > mm-khugepaged-avoid-overriding-min_free_kbytes-set-by-user.patch -- Michal Hocko SUSE Labs
