Home » Mailing lists » Devel » [PATCH 00/11] kmem controller for memcg: stripped down version
| Re: [PATCH 02/11] memcg: Reclaim when more than one page needed. [message #46964 is a reply to message #46951] |
Tue, 26 June 2012 07:12   |
Glauber Costa
Messages: 916
Registered: October 2011
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Senior Member |
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>
>> + * retries
>> + */
>> +#define NR_PAGES_TO_RETRY 2
>> +
>
> Should be 1 << PAGE_ALLOC_COSTLY_ORDER? Where does this number come from?
> The changelog doesn't specify.
Hocko complained about that, and I changed. Where the number comes from,
is stated in the comments: it is a number small enough to have high
changes of had been freed by the previous reclaim, and yet around the
number of pages of a kernel allocation.
Of course there are allocations for nr_pages > 2. But 2 will already
service the stack most of the time, and most of the slab caches.
>> static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>> - unsigned int nr_pages, bool oom_check)
>> + unsigned int nr_pages, unsigned int min_pages,
>> + bool oom_check)
>> {
>> unsigned long csize = nr_pages * PAGE_SIZE;
>> struct mem_cgroup *mem_over_limit;
>> @@ -2182,18 +2190,18 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>> } else
>> mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
>> /*
>> - * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
>> - * of regular pages (CHARGE_BATCH), or a single regular page (1).
>> - *
>> * Never reclaim on behalf of optional batching, retry with a
>> * single page instead.
>> */
>> - if (nr_pages == CHARGE_BATCH)
>> + if (nr_pages > min_pages)
>> return CHARGE_RETRY;
>>
>> if (!(gfp_mask & __GFP_WAIT))
>> return CHARGE_WOULDBLOCK;
>>
>> + if (gfp_mask & __GFP_NORETRY)
>> + return CHARGE_NOMEM;
>> +
>> ret = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
>> if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
>> return CHARGE_RETRY;
>> @@ -2206,7 +2214,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>> * unlikely to succeed so close to the limit, and we fall back
>> * to regular pages anyway in case of failure.
>> */
>> - if (nr_pages == 1 && ret)
>> + if (nr_pages <= NR_PAGES_TO_RETRY && ret)
>> return CHARGE_RETRY;
>>
>> /*
>> @@ -2341,7 +2349,8 @@ again:
>> nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
>> }
>>
>> - ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, oom_check);
>> + ret = mem_cgroup_do_charge(memcg, gfp_mask, batch, nr_pages,
>> + oom_check);
>> switch (ret) {
>> case CHARGE_OK:
>> break;
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