Eric Lee / linux-smarc-t335x-v3.2

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Commit 22a668d7c3ef833e7d67e9cef587ecc78069d532

Authored by KAMEZAWA Hiroyuki
Committed by Linus Torvalds
1 parent 8a9478ca7f
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

memcg: fix behavior under memory.limit equals to memsw.limit 

A user can set memcg.limit_in_bytes == memcg.memsw.limit_in_bytes when the
user just want to limit the total size of applications, in other words,
not very interested in memory usage itself.  In this case, swap-out will
be done only by global-LRU.

But, under current implementation, memory.limit_in_bytes is checked at
first and try_to_free_page() may do swap-out.  But, that swap-out is
useless for memsw.limit_in_bytes and the thread may hit limit again.

This patch tries to fix the current behavior at memory.limit ==
memsw.limit case.  And documentation is updated to explain the behavior of
this special case.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 2 changed files with 30 additions and 6 deletions Side-by-side Diff

Documentation/cgroups/memory.txt
Diff comments   View file @ 22a668d
... ... @@ -152,14 +152,19 @@
152 152  
153 153 usage of mem+swap is limited by memsw.limit_in_bytes.
154 154  
155   -Note: why 'mem+swap' rather than swap.
  155 +* why 'mem+swap' rather than swap.
156 156 The global LRU(kswapd) can swap out arbitrary pages. Swap-out means
157 157 to move account from memory to swap...there is no change in usage of
158   -mem+swap.
  158 +mem+swap. In other words, when we want to limit the usage of swap without
  159 +affecting global LRU, mem+swap limit is better than just limiting swap from
  160 +OS point of view.
159 161  
160   -In other words, when we want to limit the usage of swap without affecting
161   -global LRU, mem+swap limit is better than just limiting swap from OS point
162   -of view.
  162 +* What happens when a cgroup hits memory.memsw.limit_in_bytes
  163 +When a cgroup his memory.memsw.limit_in_bytes, it's useless to do swap-out
  164 +in this cgroup. Then, swap-out will not be done by cgroup routine and file
  165 +caches are dropped. But as mentioned above, global LRU can do swapout memory
  166 +from it for sanity of the system's memory management state. You can't forbid
  167 +it by cgroup.
163 168  
164 169 2.5 Reclaim
165 170  
... ... @@ -177,6 +177,9 @@
177 177  
178 178 unsigned int swappiness;
179 179  
  180 + /* set when res.limit == memsw.limit */
  181 + bool memsw_is_minimum;
  182 +
180 183 /*
181 184 * statistics. This must be placed at the end of memcg.
182 185 */
... ... @@ -847,6 +850,10 @@
847 850 int ret, total = 0;
848 851 int loop = 0;
849 852  
  853 + /* If memsw_is_minimum==1, swap-out is of-no-use. */
  854 + if (root_mem->memsw_is_minimum)
  855 + noswap = true;
  856 +
850 857 while (loop < 2) {
851 858 victim = mem_cgroup_select_victim(root_mem);
852 859 if (victim == root_mem)
... ... @@ -1752,6 +1759,12 @@
1752 1759 break;
1753 1760 }
1754 1761 ret = res_counter_set_limit(&memcg->res, val);
  1762 + if (!ret) {
  1763 + if (memswlimit == val)
  1764 + memcg->memsw_is_minimum = true;
  1765 + else
  1766 + memcg->memsw_is_minimum = false;
  1767 + }
1755 1768 mutex_unlock(&set_limit_mutex);
1756 1769  
1757 1770 if (!ret)
... ... @@ -1799,6 +1812,12 @@
1799 1812 break;
1800 1813 }
1801 1814 ret = res_counter_set_limit(&memcg->memsw, val);
  1815 + if (!ret) {
  1816 + if (memlimit == val)
  1817 + memcg->memsw_is_minimum = true;
  1818 + else
  1819 + memcg->memsw_is_minimum = false;
  1820 + }
1802 1821 mutex_unlock(&set_limit_mutex);
1803 1822  
1804 1823 if (!ret)