Messages in this thread Patch in this message | | | Date | Mon, 19 Jun 2023 20:42:51 +0800 | Subject | Re: [PATCH] mm/min_free_kbytes: modify min_free_kbytes calculation rules | From | liuq <> |
| |
在 2023/6/19 11:25, Huang, Ying 写道: > Added Mel and Vlastimil. > > liuq <liuq131@chinatelecom.cn> writes: > >> The current calculation of min_free_kbytes only uses ZONE_DMA and >> ZONE_NORMAL pages,but the ZONE_MOVABLE zone->_watermark[WMARK_MIN] >> will also divide part of min_free_kbytes.This will cause the min >> watermark of ZONE_NORMAL to be too small in the presence of ZONE_MOVEABLE. > This seems like a real problem per my understanding. Can you show the > contents of /proc/zoneinfo on a problem system? > > But, per my understanding, min_free_kbytes are used for __GFP_HIGH and > PF_MEMALLOC allocations. While ZONE_MOVABLE will not be used for them > usually. So I think we should treat ZONE_MOVABLE as ZONE_HIGHMEM in > __setup_per_zone_wmarks(). > > Best Regards, > Huang, Ying On my testing machine with 16GB of memory (transparent hugepage is turned off by default), when movable zone is not configured, min_free_kbytes is 15806 (15806*15806/16=15614352kbytes, approximatel y 16G). The detailed info is as follows: [root@lq-workstation ~]# cat /proc/cmdline BOOT_IMAGE=/vmlinuz-6.2.0-rc7-00018-g0983f6bf2bfc-dirty root=/dev/mapper/ctyunos00-root ro resume=/dev/mapper/ctyunos00-swap rd.lvm.lv=ctyunos00/root rd.lvm.lv=ctyunos00/swap crashkernel=512M [root@lq-workstation ~]# cat /proc/zoneinfo |grep -A 5 min min 3 low 6 high 9 spanned 4095 present 3998 managed 3840 -- min 328 low 652 high 976 spanned 1044480 present 478802 managed 330969 -- min 3618 low 7193 high 10768 spanned 3655680 present 3655680 managed 3575787 -- min 0 low 0 high 0 spanned 0 present 0 managed 0 [root@lq-workstation ~]# cat /proc/sys/vm/min_free_kbytes 15806
If movablecore=12G is configured, at this time, min_free_kbytes is 7326 (7326 * 7326/16=3354392, approximately 16G-12G) The detailed info is as follows: [root@lq-workstation ~]# cat /proc/cmdline BOOT_IMAGE=/vmlinuz-6.2.0-rc7-00018-g0983f6bf2bfc-dirty root=/dev/mapper/ctyunos00-root ro resume=/dev/mapper/ctyunos00-swap rd.lvm.lv=ctyunos00/root rd.lvm.lv=ctyunos00/swap crashkernel=512M movablecore=12G [root@lq-workstation ~]# cat /proc/zoneinfo |grep -A 5 min min 1 low 4 high 7 spanned 4095 present 3998 managed 3840 -- min 152 low 476 high 800 spanned 1044480 present 478802 managed 330969 -- min 239 low 748 high 1257 spanned 509952 present 509952 managed 509952 -- min 1437 low 4502 high 7567 spanned 3145728 present 3145728 managed 3065833 [root@lq-workstation ~]# cat /proc/sys/vm/min_free_kbytes 7326
After this patch is added, the configuration of the movable zone no longer affects the size of the min_free_kbytes, which is only affected by the size of the available memory. >> Signed-off-by: liuq <liuq131@chinatelecom.cn> >> --- >> include/linux/mm.h | 1 + >> mm/khugepaged.c | 2 +- >> mm/page_alloc.c | 15 ++++++++++++++- >> 3 files changed, 16 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index cf3d0d673f6b..1f91d035bcaf 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -863,6 +863,7 @@ void split_page(struct page *page, unsigned int order); >> void folio_copy(struct folio *dst, struct folio *src); >> >> unsigned long nr_free_buffer_pages(void); >> +unsigned long nr_free_pagecache_pages(void); >> >> /* >> * Compound pages have a destructor function. Provide a >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index 16be62d493cd..6632264b951c 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -2342,7 +2342,7 @@ static void set_recommended_min_free_kbytes(void) >> >> /* don't ever allow to reserve more than 5% of the lowmem */ >> recommended_min = min(recommended_min, >> - (unsigned long) nr_free_buffer_pages() / 20); >> + (unsigned long) nr_free_pagecache_pages() / 20); >> recommended_min <<= (PAGE_SHIFT-10); >> >> if (recommended_min > min_free_kbytes) { >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index e008a3df0485..489b564526dd 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -5775,6 +5775,19 @@ unsigned long nr_free_buffer_pages(void) >> } >> EXPORT_SYMBOL_GPL(nr_free_buffer_pages); >> >> +/** >> + * nr_free_pagecache_pages - count number of pages beyond high watermark >> + * >> + * nr_free_pagecache_pages() counts the number of pages which are beyond the >> + * high watermark within all zones. >> + * >> + * Return: number of pages beyond high watermark within all zones. >> + */ >> +unsigned long nr_free_pagecache_pages(void) >> +{ >> + return nr_free_zone_pages(gfp_zone(GFP_HIGHUSER_MOVABLE)); >> +} >> + >> static inline void show_node(struct zone *zone) >> { >> if (IS_ENABLED(CONFIG_NUMA)) >> @@ -8651,7 +8664,7 @@ void calculate_min_free_kbytes(void) >> unsigned long lowmem_kbytes; >> int new_min_free_kbytes; >> >> - lowmem_kbytes = nr_free_buffer_pages() * (PAGE_SIZE >> 10); >> + lowmem_kbytes = nr_free_pagecache_pages() * (PAGE_SIZE >> 10); >> new_min_free_kbytes = int_sqrt(lowmem_kbytes * 16); >> >> if (new_min_free_kbytes > user_min_free_kbytes)
| |