The patch titled Subject: mm/page_alloc.c: only tune sysctl_lowmem_reserve_ratio value once when changing it has been added to the -mm tree. Its filename is mm-page_allocc-only-tune-sysctl_lowmem_reserve_ratio-value-once-when-changing-it.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-page_allocc-only-tune-sysctl_lowmem_reserve_ratio-value-once-when-changing-it.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_allocc-only-tune-sysctl_lowmem_reserve_ratio-value-once-when-changing-it.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Baoquan He <bhe@xxxxxxxxxx> Subject: mm/page_alloc.c: only tune sysctl_lowmem_reserve_ratio value once when changing it Patch series "improvements about lowmem_reserve and /proc/zoneinfo", v2. This patch (of 3): When people write to /proc/sys/vm/lowmem_reserve_ratio to change sysctl_lowmem_reserve_ratio[], setup_per_zone_lowmem_reserve() is called to recalculate all ->lowmem_reserve[] for each zone of all nodes as below: static void setup_per_zone_lowmem_reserve(void) { ... for_each_online_pgdat(pgdat) { for (j = 0; j < MAX_NR_ZONES; j++) { ... while (idx) { ... if (sysctl_lowmem_reserve_ratio[idx] < 1) { sysctl_lowmem_reserve_ratio[idx] = 0; lower_zone->lowmem_reserve[j] = 0; } else { ... } } } } Meanwhile, here, sysctl_lowmem_reserve_ratio[idx] will be tuned if its value is smaller than '1'. As we know, sysctl_lowmem_reserve_ratio[] is set for zone without regarding to which node it belongs to. That means the tuning will be done on all nodes, even though it has been done in the first node. And the tuning will be done too even when init_per_zone_wmark_min() calls setup_per_zone_lowmem_reserve(), where actually nobody tries to change sysctl_lowmem_reserve_ratio[]. So now move the tuning into lowmem_reserve_ratio_sysctl_handler(), to make code logic more reasonable. Link: http://lkml.kernel.org/r/20200402140113.3696-1-bhe@xxxxxxxxxx Link: http://lkml.kernel.org/r/20200402140113.3696-2-bhe@xxxxxxxxxx Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- a/mm/page_alloc.c~mm-page_allocc-only-tune-sysctl_lowmem_reserve_ratio-value-once-when-changing-it +++ a/mm/page_alloc.c @@ -7702,8 +7702,7 @@ static void setup_per_zone_lowmem_reserv idx--; lower_zone = pgdat->node_zones + idx; - if (sysctl_lowmem_reserve_ratio[idx] < 1) { - sysctl_lowmem_reserve_ratio[idx] = 0; + if (!sysctl_lowmem_reserve_ratio[idx]) { lower_zone->lowmem_reserve[j] = 0; } else { lower_zone->lowmem_reserve[j] = @@ -7968,7 +7967,15 @@ int sysctl_min_slab_ratio_sysctl_handler int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos) { + int i; + proc_dointvec_minmax(table, write, buffer, length, ppos); + + for (i = 0; i < MAX_NR_ZONES; i++) { + if (sysctl_lowmem_reserve_ratio[i] < 1) + sysctl_lowmem_reserve_ratio[i] = 0; + } + setup_per_zone_lowmem_reserve(); return 0; } _ Patches currently in -mm which might be from bhe@xxxxxxxxxx are mm-memmap_init-iterate-over-memblock-regions-rather-that-check-each-pfn.patch mm-remove-unused-free_bootmem_with_active_regions.patch mm-page_allocc-only-tune-sysctl_lowmem_reserve_ratio-value-once-when-changing-it.patch mm-page_allocc-clear-out-zone-lowmem_reserve-if-the-zone-is-empty.patch mm-vmstatc-do-not-show-lowmem-reserve-protection-information-of-empty-zone.patch