On 03/06/2013 05:07 AM, Kamezawa Hiroyuki wrote:
> (2013/03/05 22:10), Glauber Costa wrote:
>> If we are not using memcg, there is no reason why we should allocate
>> this structure, that will be a memory waste at best. We can do better
>> at least in the sparsemem case, and allocate it when the first cgroup
>> is requested. It should now not panic on failure, and we have to handle
>> this right.
>>
>> flatmem case is a bit more complicated, so that one is left out for
>> the moment.
>>
>> Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx>
>> CC: Michal Hocko <mhocko@xxxxxxx>
>> CC: Kamezawa Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
>> CC: Johannes Weiner <hannes@xxxxxxxxxxx>
>> CC: Mel Gorman <mgorman@xxxxxxx>
>> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>> ---
>> include/linux/page_cgroup.h | 28 +++++----
>> init/main.c | 2 -
>> mm/memcontrol.c | 3 +-
>> mm/page_cgroup.c | 150 ++++++++++++++++++++++++--------------------
>> 4 files changed, 99 insertions(+), 84 deletions(-)
>
> This patch seems a complicated mixture of clean-up and what-you-really-want.
>
I swear it is all what-I-really-want, any cleanups are non-intentional!
>> -#if !defined(CONFIG_SPARSEMEM)
>> +static void *alloc_page_cgroup(size_t size, int nid)
>> +{
>> + gfp_t flags = GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN;
>> + void *addr = NULL;
>> +
>> + addr = alloc_pages_exact_nid(nid, size, flags);
>> + if (addr) {
>> + kmemleak_alloc(addr, size, 1, flags);
>> + return addr;
>> + }
>
> As far as I remember, this function was written for SPARSEMEM.
>
> How big this "size" will be with FLATMEM/DISCONTIGMEM ?
> if 16GB, 16 * 1024 * 1024 * 1024 / 4096 * 16 = 64MB.
>
> What happens if order > MAX_ORDER is passed to alloc_pages()...no warning ?
>
> How about using vmalloc always if not SPARSEMEM ?
I don't oppose.
>>
>> -void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)
>> +static void free_page_cgroup(void *addr)
>> +{
>> + if (is_vmalloc_addr(addr)) {
>> + vfree(addr);
>> + } else {
>> + struct page *page = virt_to_page(addr);
>> + int nid = page_to_nid(page);
>> + BUG_ON(PageReserved(page));
>
> This BUG_ON() can be removed.
>
You are right, although it is still a bug =)
>> + free_pages_exact(addr, page_cgroup_table_size(nid));
>> + }
>> +}
>> +
>> +static void page_cgroup_msg(void)
>> +{
>> + printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
>> + printk(KERN_INFO "please try 'cgroup_disable=memory' option if you "
>> + "don't want memory cgroups.\nAlternatively, consider "
>> + "deferring your memory cgroups creation.\n");
>> +}
>
> I think this warning can be removed because it's not boot option problem
> after this patch. I guess the boot option can be obsolete....
>
I think it is extremely useful, at least during the next couple of
releases. A lot of distributions will create memcgs for no apparent
reasons way before they are used (if used at all), as a placeholder only.
This can at least tell them that there is a way to stop paying a memory
penalty (together with the actual memory footprint)
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