每个zone的low memory是怎么计算出来的

Posted 2021-01-22 honpey

deferred_init_memmap

-->deferred_free_range

 

 

6801 /*
6802  * Initialise min_free_kbytes.
6803  *
6804  * For small machines we want it small (128k min).  For large machines
6805  * we want it large (64MB max).  But it is not linear, because network
6806  * bandwidth does not increase linearly with machine size.  We use
6807  *
6808  *  min_free_kbytes = 4 * sqrt(lowmem_kbytes), for better accuracy:
6809  *  min_free_kbytes = sqrt(lowmem_kbytes * 16)
6810  *
6811  * which yields
6812  *
6813  * 16MB:    512k
6814  * 32MB:    724k
6815  * 64MB:    1024k
6816  * 128MB:   1448k
6817  * 256MB:   2048k
6818  * 512MB:   2896k
6819  * 1024MB:  4096k
6820  * 2048MB:  5792k
6821  * 4096MB:  8192k
6822  * 8192MB:  11584k
6823  * 16384MB: 16384k
6824  */
6825 int __meminit init_per_zone_wmark_min(void)
6826 {
6827     unsigned long lowmem_kbytes;
6828     int new_min_free_kbytes;
6829
6830

 

6726 static void __setup_per_zone_wmarks(void)
6727 {
6728     unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
6729     unsigned long lowmem_pages = 0;
6730     struct zone *zone;
6731     unsigned long flags;
6732
6733     /* Calculate total number of !ZONE_HIGHMEM pages */
6734     for_each_zone(zone) {
6735         if (!is_highmem(zone))
6736             lowmem_pages += zone->managed_pages;
6737     }
6738
6739     for_each_zone(zone) {
6740         u64 tmp;
6741
6742         spin_lock_irqsave(&zone->lock, flags);
6743