Hi, Kefeng, Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> writes: > Hi Liuq, > > On 2023/6/21 17:20, liuq wrote: >> 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. >> __GFP_HIGH and PF_MEMALLOC allocations usually don't need movable >> zone pages, so just like ZONE_HIGHMEM, cap pages_min to a small >> value in __setup_per_zone_wmarks. >> On my testing machine with 16GB of memory (transparent hugepage is >> turned off by default, and movablecore=12G is configured) >> The following is a comparative test data of watermark_min >> no patch add patch >> ZONE_DMA 1 8 >> ZONE_DMA32 151 709 >> ZONE_NORMAL 233 1113 >> ZONE_MOVABLE 1434 128 >> min_free_kbytes 7288 7326 >> > > We see this issue and do the same change[1], and we add a per zone > watermark configuration too, but both of them is not accepted, > let's add Mel and wupeng to see more comments. > > [1]https://lore.kernel.org/linux-mm/20220905032858.1462927-1-mawupeng1@xxxxxxxxxx/ Thanks for your information! That's very useful. As Mel said, ZONE_MOVABLE or ZONE_HIGHMEM pages allocation will need low memory to be allocated too. But I don't understand why higher min watermark of ZONE_MOVABLE will help this. It's too small compared with the size of ZONE_MOVABLE in most cases. For example, on the system of the patch description, the original "large" min watermark of ZONE_MOVABLE is only (1434 * 4) = 5736 KB, which is too small compared with 12 GB total ZONE_MOVABLE size. That is, before reaching min or low watermark, we will allocate almost same number of ZONE_MOVABLE pages: ~12GB vs. ~(12GB - 5MB). Best Regards, Huang, Ying >> Signed-off-by: liuq <liuq131@xxxxxxxxxxxxxxx> >> --- >> mm/page_alloc.c | 12 ++++++------ >> 1 file changed, 6 insertions(+), 6 deletions(-) >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 47421bedc12b..590ed8725e09 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -6362,9 +6362,9 @@ static void __setup_per_zone_wmarks(void) >> struct zone *zone; >> unsigned long flags; >> - /* Calculate total number of !ZONE_HIGHMEM pages */ >> + /* Calculate total number of !ZONE_HIGHMEM and !ZONE_MOVABLE pages */ >> for_each_zone(zone) { >> - if (!is_highmem(zone)) >> + if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE) >> lowmem_pages += zone_managed_pages(zone); >> } >> @@ -6374,15 +6374,15 @@ static void __setup_per_zone_wmarks(void) >> spin_lock_irqsave(&zone->lock, flags); >> tmp = (u64)pages_min * zone_managed_pages(zone); >> do_div(tmp, lowmem_pages); >> - if (is_highmem(zone)) { >> + if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) { >> /* >> * __GFP_HIGH and PF_MEMALLOC allocations usually don't >> - * need highmem pages, so cap pages_min to a small >> - * value here. >> + * need highmem and movable zones pages, so cap pages_min >> + * to a small value here. >> * >> * The WMARK_HIGH-WMARK_LOW and (WMARK_LOW-WMARK_MIN) >> * deltas control async page reclaim, and so should >> - * not be capped for highmem. >> + * not be capped for highmem and movable zones. >> */ >> unsigned long min_pages; >>
