Messages in this thread | | | Subject | Re: [PATCH 2/3] mm/memcg: Simplify mem_cgroup_get_max() | From | Waiman Long <> | Date | Thu, 20 Aug 2020 16:29:27 -0400 |
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On 8/20/20 1:35 PM, Johannes Weiner wrote: > On Thu, Aug 20, 2020 at 09:03:49AM -0400, Waiman Long wrote: >> The mem_cgroup_get_max() function used to get memory+swap max from >> both the v1 memsw and v2 memory+swap page counters & return the maximum >> of these 2 values. This is redundant and it is more efficient to just >> get either the v1 or the v2 values depending on which one is currently >> in use. >> >> Signed-off-by: Waiman Long <longman@redhat.com> >> --- >> mm/memcontrol.c | 14 +++++--------- >> 1 file changed, 5 insertions(+), 9 deletions(-) >> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index 26b7a48d3afb..d219dca5239f 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -1633,17 +1633,13 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) >> */ >> unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg) >> { >> - unsigned long max; >> + unsigned long max = READ_ONCE(memcg->memory.max); >> >> - max = READ_ONCE(memcg->memory.max); >> if (mem_cgroup_swappiness(memcg)) { >> - unsigned long memsw_max; >> - unsigned long swap_max; >> - >> - memsw_max = memcg->memsw.max; >> - swap_max = READ_ONCE(memcg->swap.max); >> - swap_max = min(swap_max, (unsigned long)total_swap_pages); >> - max = min(max + swap_max, memsw_max); >> + if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) >> + max += READ_ONCE(memcg->swap.max); >> + else >> + max = memcg->memsw.max; > I agree with the premise of the patch, but v1 and v2 have sufficiently > different logic, and the way v1 overrides max from the innermost > branch again also doesn't help in understanding what's going on. > > Can you please split out the v1 and v2 code? > > if (cgroup_subsys_on_dfl(memory_cgrp_subsys)) { > max = READ_ONCE(memcg->memory.max); > if (mem_cgroup_swappiness(memcg)) > max += READ_ONCE(memcg->swap.max); > } else { > if (mem_cgroup_swappiness(memcg)) > max = memcg->memsw.max; > else > max = READ_ONCE(memcg->memory.max); > } > > It's slightly repetitive, but IMO much more readable. > Sure. That makes it even better.
Cheers, Longman
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