[v3 0/2] recalculate min_free_kbytes post memory hotplug

[v3 0/2] recalculate min_free_kbytes post memory hotplug

[Vijay Balakrishna]

v2 -> v3
--------
[v2 1/2]
- removed symptoms references from changelog

[v2 2/2]
- addressed following issues Michal Hocko raised:
  . nr_free_buffer_pages can oveflow in int on very large machines
  . min_free_kbytes can decrease the size theoretically

v1 -> v2
--------
- addressed issue Kirill A. Shutemov raised:
  . changes would override min_free_kbytes set by user

Vijay Balakrishna (2):
  mm: khugepaged: recalculate min_free_kbytes after memory hotplug as
    expected by khugepaged
  mm: khugepaged: avoid overriding min_free_kbytes set by user

 include/linux/khugepaged.h |  5 +++++
 mm/khugepaged.c            | 16 +++++++++++++---
 mm/memory_hotplug.c        |  3 +++
 mm/page_alloc.c            |  2 +-
 4 files changed, 22 insertions(+), 4 deletions(-)

-- 
2.28.0

[v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Vijay Balakrishna]

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 change restores min_free_kbytes
as expected for THP consumers.

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

[v3 2/2] mm: khugepaged: avoid overriding min_free_kbytes set by user

[Vijay Balakrishna]

set_recommended_min_free_kbytes need to honor min_free_kbytes set by the
user.  Post start-of-day THP enable or memory hotplug operations can
lose user specified min_free_kbytes, in particular when it is higher than
calculated recommended value.  user_min_free_kbytes initialized to 0
to avoid undesired result when comparing with  "unsigned long" type.

Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
Cc: stable@vger.kernel.org
Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
---
 mm/khugepaged.c | 3 ++-
 mm/page_alloc.c | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 4f7107476a6f..3c1147816d12 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2283,7 +2283,8 @@ static void set_recommended_min_free_kbytes(void)
 			      (unsigned long) nr_free_buffer_pages() / 20);
 	recommended_min <<= (PAGE_SHIFT-10);
 
-	if (recommended_min > min_free_kbytes) {
+	if (recommended_min > min_free_kbytes ||
+		recommended_min > user_min_free_kbytes) {
 		if (user_min_free_kbytes >= 0)
 			pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
 				min_free_kbytes, recommended_min);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fab5e97dc9ca..7b81fb139034 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -315,7 +315,7 @@ compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
 };
 
 int min_free_kbytes = 1024;
-int user_min_free_kbytes = -1;
+int user_min_free_kbytes = 0;
 #ifdef CONFIG_DISCONTIGMEM
 /*
  * DiscontigMem defines memory ranges as separate pg_data_t even if the ranges
-- 
2.28.0

Re: [v3 2/2] mm: khugepaged: avoid overriding min_free_kbytes set by user

[Vijay Balakrishna]

Please ignore this patch.  I forgot to run scripts/checkpatch.pl and see

CHECK: Alignment should match open parenthesis
#30: FILE: mm/khugepaged.c:2287:
+       if (recommended_min > min_free_kbytes ||
+               recommended_min > user_min_free_kbytes) {

ERROR: do not initialise globals to 0
#43: FILE: mm/page_alloc.c:318:
+int user_min_free_kbytes = 0;

Sorry for trouble, I will send a new version.

Vijay

On 9/16/2020 6:21 PM, Vijay Balakrishna wrote:
> set_recommended_min_free_kbytes need to honor min_free_kbytes set by the
> user.  Post start-of-day THP enable or memory hotplug operations can
> lose user specified min_free_kbytes, in particular when it is higher than
> calculated recommended value.  user_min_free_kbytes initialized to 0
> to avoid undesired result when comparing with  "unsigned long" type.
> 
> Signed-off-by: Vijay Balakrishna <vijayb@linux.microsoft.com>
> Cc: stable@vger.kernel.org
> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
> ---
>   mm/khugepaged.c | 3 ++-
>   mm/page_alloc.c | 2 +-
>   2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 4f7107476a6f..3c1147816d12 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -2283,7 +2283,8 @@ static void set_recommended_min_free_kbytes(void)
>   			      (unsigned long) nr_free_buffer_pages() / 20);
>   	recommended_min <<= (PAGE_SHIFT-10);
>   
> -	if (recommended_min > min_free_kbytes) {
> +	if (recommended_min > min_free_kbytes ||
> +		recommended_min > user_min_free_kbytes) {
>   		if (user_min_free_kbytes >= 0)
>   			pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
>   				min_free_kbytes, recommended_min);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index fab5e97dc9ca..7b81fb139034 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -315,7 +315,7 @@ compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {
>   };
>   
>   int min_free_kbytes = 1024;
> -int user_min_free_kbytes = -1;
> +int user_min_free_kbytes = 0;
>   #ifdef CONFIG_DISCONTIGMEM
>   /*
>    * DiscontigMem defines memory ranges as separate pg_data_t even if the ranges
> 

Re: [v3 2/2] mm: khugepaged: avoid overriding min_free_kbytes set by user

[Sasha Levin]

Hi

[This is an automated email]

This commit has been processed because it contains a -stable tag.
The stable tag indicates that it's relevant for the following trees: all

The bot has tested the following trees: v5.8.10, v5.4.66, v4.19.146, v4.14.198, v4.9.236, v4.4.236.

v5.8.10: Build OK!
v5.4.66: Build OK!
v4.19.146: Failed to apply! Possible dependencies:
    1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
    24512228b7a3 ("mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model")
    426dcd4b600f ("hexagon: switch to NO_BOOTMEM")
    6471f52af786 ("alpha: switch to NO_BOOTMEM")
    6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation")
    9705bea5f833 ("mm: convert zone->managed_pages to atomic variable")
    a921444382b4 ("mm: move zone watermark accesses behind an accessor")
    b4a991ec584b ("mm: remove CONFIG_NO_BOOTMEM")
    bc3ec75de545 ("dma-mapping: merge direct and noncoherent ops")
    bda49a81164a ("mm: remove nobootmem")
    c32e64e852f3 ("csky: Build infrastructure")
    e0a9317d9004 ("hexagon: use generic dma_noncoherent_ops")
    f406f222d4b2 ("hexagon: implement the sync_sg_for_device DMA operation")

v4.14.198: Failed to apply! Possible dependencies:
    1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
    1d47a3ec09b5 ("mm/cma: remove ALLOC_CMA")
    24512228b7a3 ("mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model")
    3d2054ad8c2d ("ARM: CMA: avoid double mapping to the CMA area if CONFIG_HIGHMEM=y")
    453f85d43fa9 ("mm: remove __GFP_COLD")
    6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation")
    85ccc8fa81af ("mm/page_alloc: make sure __rmqueue() etc are always inline")
    a921444382b4 ("mm: move zone watermark accesses behind an accessor")
    bad8c6c0b114 ("mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE")

v4.9.236: Failed to apply! Possible dependencies:
    14b468791fa9 ("mm: workingset: move shadow entry tracking to radix tree exceptional tracking")
    1c30844d2dfe ("mm: reclaim small amounts of memory when an external fragmentation event occurs")
    24512228b7a3 ("mm: do not boost watermarks to avoid fragmentation for the DISCONTIG memory model")
    2a2e48854d70 ("mm: vmscan: fix IO/refault regression in cache workingset transition")
    31176c781508 ("mm: memcontrol: clean up memory.events counting function")
    6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation")
    8e675f7af507 ("mm/oom_kill: count global and memory cgroup oom kills")
    9d998b4f1e39 ("mm, vmscan: add active list aging tracepoint")
    a921444382b4 ("mm: move zone watermark accesses behind an accessor")
    cd04ae1e2dc8 ("mm, oom: do not rely on TIF_MEMDIE for memory reserves access")
    d6622f6365db ("mm/vmscan: more restrictive condition for retry in do_try_to_free_pages")
    dcec0b60a821 ("mm, vmscan: add mm_vmscan_inactive_list_is_low tracepoint")
    df0e53d0619e ("mm: memcontrol: re-use global VM event enum")
    f7942430e40f ("lib: radix-tree: native accounting of exceptional entries")

v4.4.236: Failed to apply! Possible dependencies:
    0b57d6ba0bd1 ("mm/mmap.c: remove redundant local variables for may_expand_vm()")
    1170532bb49f ("mm: convert printk(KERN_<LEVEL> to pr_<level>")
    5a6e75f8110c ("shmem: prepare huge= mount option and sysfs knob")
    756a025f0009 ("mm: coalesce split strings")
    84638335900f ("mm: rework virtual memory accounting")
    8cee852ec53f ("mm, procfs: breakdown RSS for anon, shmem and file in /proc/pid/status")
    b46e756f5e47 ("thp: extract khugepaged from mm/huge_memory.c")
    d07e22597d1d ("mm: mmap: add new /proc tunable for mmap_base ASLR")
    d977d56ce5b3 ("mm: warn about VmData over RLIMIT_DATA")
    d9fe4fab1197 ("x86/mm/pat: Add untrack_pfn_moved for mremap")
    eca56ff906bd ("mm, shmem: add internal shmem resident memory accounting")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

-- 
Thanks
Sasha

Re: [v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Sasha Levin]

Hi

[This is an automated email]

This commit has been processed because it contains a "Fixes:" tag
fixing commit: f000565adb77 ("thp: set recommended min free kbytes").

The bot has tested the following trees: v5.8.10, v5.4.66, v4.19.146, v4.14.198, v4.9.236, v4.4.236.

v5.8.10: Build OK!
v5.4.66: Build OK!
v4.19.146: Failed to apply! Possible dependencies:
    013de2d6671d ("csky: MMU and page table management")
    27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
    426dcd4b600f ("hexagon: switch to NO_BOOTMEM")
    6471f52af786 ("alpha: switch to NO_BOOTMEM")
    9143a9359d05 ("csky: Kernel booting")
    aca52c398389 ("mm: remove CONFIG_HAVE_MEMBLOCK")
    bc3ec75de545 ("dma-mapping: merge direct and noncoherent ops")
    c32e64e852f3 ("csky: Build infrastructure")
    ca9a46f8a4f0 ("mm/memory_hotplug: online_pages cannot be 0 in online_pages()")
    de1193f0be66 ("mm, memory_hotplug: update pcp lists everytime onlining a memory block")
    e0a9317d9004 ("hexagon: use generic dma_noncoherent_ops")
    e900a918b098 ("mm: shuffle initial free memory to improve memory-side-cache utilization")
    f3ecc0ff0457 ("dma-mapping: move the dma_coherent flag to struct device")
    f406f222d4b2 ("hexagon: implement the sync_sg_for_device DMA operation")

v4.14.198: Failed to apply! Possible dependencies:
    008ef0969dd9 ("btrfs: drop lock parameter from update_ioctl_balance_args and rename")
    17ef445f9bef ("Documentation/filesystems: update documentation of file_operations")
    27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
    3d8f7615319b ("vfs: implement readahead(2) using POSIX_FADV_WILLNEED")
    45cd0faae371 ("vfs: add the fadvise() file operation")
    5740c99e9d30 ("vfs: dedupe: return int")
    6e8b704df584 ("fs: update documentation to mention __poll_t and match the code")
    87eb5eb24232 ("vfs: dedupe: rationalize args")
    b4e98d9ac775 ("mm: account pud page tables")
    c4812909f5d5 ("mm: introduce wrappers to access mm->nr_ptes")
    ca9a46f8a4f0 ("mm/memory_hotplug: online_pages cannot be 0 in online_pages()")
    de1193f0be66 ("mm, memory_hotplug: update pcp lists everytime onlining a memory block")
    e900a918b098 ("mm: shuffle initial free memory to improve memory-side-cache utilization")
    f51d2b59120f ("btrfs: allow to set compression level for zlib")
    f5c29bd9dbd3 ("Btrfs: add __init macro to btrfs init functions")

v4.9.236: Failed to apply! Possible dependencies:
    0b89ede62963 ("s390/mm: fork vs. 5 level page tabel")
    27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
    505a60e22560 ("asm-generic: introduce 5level-fixup.h")
    a00cc7d9dd93 ("mm, x86: add support for PUD-sized transparent hugepages")
    b4e98d9ac775 ("mm: account pud page tables")
    c2febafc6773 ("mm: convert generic code to 5-level paging")
    c4812909f5d5 ("mm: introduce wrappers to access mm->nr_ptes")
    c763ea2650df ("x86/kconfig: Sort the 'config X86' selects alphabetically")
    d94e068573f2 ("x86/kconfig: Move 64-bit only arch Kconfig selects to 'config X86_64'")

v4.4.236: Failed to apply! Possible dependencies:
    0b57d6ba0bd1 ("mm/mmap.c: remove redundant local variables for may_expand_vm()")
    1170532bb49f ("mm: convert printk(KERN_<LEVEL> to pr_<level>")
    27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP")
    5a6e75f8110c ("shmem: prepare huge= mount option and sysfs knob")
    756a025f0009 ("mm: coalesce split strings")
    84638335900f ("mm: rework virtual memory accounting")
    8cee852ec53f ("mm, procfs: breakdown RSS for anon, shmem and file in /proc/pid/status")
    b46e756f5e47 ("thp: extract khugepaged from mm/huge_memory.c")
    d07e22597d1d ("mm: mmap: add new /proc tunable for mmap_base ASLR")
    d977d56ce5b3 ("mm: warn about VmData over RLIMIT_DATA")
    d9fe4fab1197 ("x86/mm/pat: Add untrack_pfn_moved for mremap")
    eca56ff906bd ("mm, shmem: add internal shmem resident memory accounting")


NOTE: The patch will not be queued to stable trees until it is upstream.

How should we proceed with this patch?

-- 
Thanks
Sasha

Re: [v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Vijay Balakrishna]

Can this patch be included?  As Kirill is ok with patch now.

Thanks,
Vijay

On 9/16/2020 6:21 PM, 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 change restores min_free_kbytes
> as expected for THP consumers.
> 
> 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);
> 

Re: [v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Andrew Morton]

On Wed, 23 Sep 2020 14:27:30 -0700 Vijay Balakrishna <vijayb@linux.microsoft.com> wrote:

> Can this patch be included?  As Kirill is ok with patch now.

He is?  I can't immediately find that email.

Do we have an acked-by?

Re: [v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Michal Hocko]

On Wed 16-09-20 18:21:48, 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 change restores min_free_kbytes
> as expected for THP consumers.
> 
> 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>

I am ok with this patch. I am not sure this is worth backporting to
stable trees becasuse this is not a functional bug. Surprising behavior,
yes, but not much more than that.

Acked-by: Michal Hocko <mhocko@suse.com>

One minor comment below
[...]
> @@ -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);

Can we move khugepaged_min_free_kbytes_update into
init_per_zone_wmark_min? If it stays external we might hit the same
problem when somebody else needs to modify min_free_kbytes. Early init
call will be likely too early for khugepaged but that shouldn't matter
AFAICS because it will call khugepaged_min_free_kbytes_update on its
own.
-- 
Michal Hocko
SUSE Labs

Re: [v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Michal Hocko]

On Thu 24-09-20 19:51:03, Andrew Morton wrote:
> On Wed, 23 Sep 2020 14:27:30 -0700 Vijay Balakrishna <vijayb@linux.microsoft.com> wrote:
> 
> > Can this patch be included?  As Kirill is ok with patch now.
> 
> He is?  I can't immediately find that email.

http://lkml.kernel.org/r/20200922070726.dlw24lf3wd3p2ias@black.fi.intel.com
-- 
Michal Hocko
SUSE Labs

Re: [v3 1/2] mm: khugepaged: recalculate min_free_kbytes after memory hotplug as expected by khugepaged

[Vijay Balakrishna]

On 9/25/2020 12:42 AM, Michal Hocko wrote:
> On Wed 16-09-20 18:21:48, 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 change restores min_free_kbytes
>> as expected for THP consumers.
>>
>> 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>
> 
> I am ok with this patch. I am not sure this is worth backporting to
> stable trees becasuse this is not a functional bug. Surprising behavior,
> yes, but not much more than that.
> 
> Acked-by: Michal Hocko <mhocko@suse.com>

Thanks Michal.

> 
> One minor comment below
> [...]
>> @@ -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);
> 
> Can we move khugepaged_min_free_kbytes_update into
> init_per_zone_wmark_min? If it stays external we might hit the same
> problem when somebody else needs to modify min_free_kbytes. Early init
> call will be likely too early for khugepaged but that shouldn't matter
> AFAICS because it will call khugepaged_min_free_kbytes_update on its
> own.

Sure, let me take a look and post v4 next week.

Thanks,
Vijay

>