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Commit 013110a7 authored by Yaowei Bai's avatar Yaowei Bai Committed by Linus Torvalds
Browse files

mm/page_alloc.c: fix a misleading comment 



The comment says that the per-cpu batchsize and zone watermarks are
determined by present_pages which is definitely wrong, they are both
calculated from managed_pages.  Fix it.

Signed-off-by: default avatarYaowei Bai <bywxiaobai@163.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c9d13f5f

Documentation/sysctl/vm.txt

+2 −2
Original line number Diff line number Diff line
@@ -349,7 +349,7 @@ zone[i]'s protection[j] is calculated by following expression. 


(i < j):

  zone[i]->protection[j]

  = (total sums of present_pages from zone[i+1] to zone[j] on the node)

  = (total sums of managed_pages from zone[i+1] to zone[j] on the node)

    / lowmem_reserve_ratio[i];

(i = j):

   (should not be protected. = 0;
@@ -360,7 +360,7 @@ The default values of lowmem_reserve_ratio[i] are 
    256 (if zone[i] means DMA or DMA32 zone)

    32  (others).

As above expression, they are reciprocal number of ratio.

256 means 1/256. # of protection pages becomes about "0.39%" of total present

256 means 1/256. # of protection pages becomes about "0.39%" of total managed

pages of higher zones on the node.



If you would like to protect more pages, smaller values are effective.

mm/page_alloc.c

+1 −1
Original line number Diff line number Diff line
@@ -6022,7 +6022,7 @@ void __init mem_init_print_info(const char *str) 
 * set_dma_reserve - set the specified number of pages reserved in the first zone

 * @new_dma_reserve: The number of pages to mark reserved

 *

 * The per-cpu batchsize and zone watermarks are determined by present_pages.

 * The per-cpu batchsize and zone watermarks are determined by managed_pages.

 * In the DMA zone, a significant percentage may be consumed by kernel image

 * and other unfreeable allocations which can skew the watermarks badly. This

 * function may optionally be used to account for unfreeable pages in the