Messages in this thread | | | Date | Mon, 30 Jun 2008 09:12:56 +0530 | From | Balbir Singh <> | Subject | Re: [RFC 5/5] Memory controller soft limit reclaim on contention |
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Paul Menage wrote: > On Fri, Jun 27, 2008 at 8:19 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote: >> +/* >> + * Create a heap of memory controller structures. The heap is reverse >> + * sorted by size. This heap is used for implementing soft limits. Our >> + * current heap implementation does not allow dynamic heap updates, but >> + * eventually, the costliest controller (over it's soft limit should > > it's -> its >
Yes
>> + old_mem = heap_insert(&mem_cgroup_heap, mem, >> + HEAP_REP_LEAF); >> + mem->on_heap = 1; >> + if (old_mem) >> + old_mem->on_heap = 0; > > Maybe a comment here that mem might == old_mem? > >> + * When the soft limit is exceeded, look through the heap and start >> + * reclaiming from all groups over thier soft limit > > thier -> their >
Will fix
>> + if (!res_counter_check_under_soft_limit(&mem->res)) { >> + /* >> + * The current task might already be over it's soft >> + * limit and trying to aggressively grow. We check to >> + * see if it the memory group associated with the >> + * current task is on the heap when the current group >> + * is over it's soft limit. If not, we add it >> + */ >> + if (!mem->on_heap) { >> + struct mem_cgroup *old_mem; >> + >> + old_mem = heap_insert(&mem_cgroup_heap, mem, >> + HEAP_REP_LEAF); >> + mem->on_heap = 1; >> + if (old_mem) >> + old_mem->on_heap = 0; >> + } >> + } > > This and the other similar code for adding to the heap should be > refactored into a separate function. >
OK, I can look into that.
>> +static int mem_cgroup_compare_soft_limits(void *p1, void *p2) >> +{ >> + struct mem_cgroup *mem1 = (struct mem_cgroup *)p1; >> + struct mem_cgroup *mem2 = (struct mem_cgroup *)p2; >> + unsigned long long delta1, delta2; >> + >> + delta1 = res_counter_soft_limit_delta(&mem1->res); >> + delta2 = res_counter_soft_limit_delta(&mem2->res); >> + >> + return delta1 > delta2; >> +} > > This isn't a valid comparator, since it isn't a constant function of > its two input pointers - calling mem_cgroup_compare_soft_limits(m1, > m2) can give different results at different times. So your heap > invariant will become invalid over time. > > I think if you want to do this, you're going to need to periodically > take a snapshot of each cgroup's excess and use that snapshot in the > comparator; whenever you update the snapshots, you'll need to restore > the heap invariant. >
I'll fix it by taking snapshots only before inserting an element into the heap (I think I responded to this one in another email, but missed out on the typos).
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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