Messages in this thread | | | Date | Wed, 24 Sep 2008 01:31:59 -0700 | From | Balbir Singh <> | Subject | Re: [PATCH 9/13] memcg: lookup page cgroup (and remove pointer from struct page) |
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KAMEZAWA Hiroyuki wrote: > On Wed, 24 Sep 2008 07:39:58 +0530 > "Balbir Singh" <balbir@linux.vnet.ibm.com> wrote: >>> I'll add FLATMEM/DISCONTIGMEM/SPARSEMEM support directly. >>> I already have wasted a month on this not-interesting work and want to fix >>> this soon. >>> >> Let's look at the basic requirement, make memory resource controller >> not suck with 32 bit systems. I have been thinking of about removing >> page_cgroup from struct page only for 32 bit systems (use radix tree), >> 32 bit systems can have a maximum of 64GB if PAE is enabled, I suspect >> radix tree should work there and let the 64 bit systems work as is. If >> performance is an issue, I would recommend the 32 bit folks upgrade to >> 64 bit :) Can we build consensus around this approach? >> > My thinking is below. (assume 64bit) >
assume 64 bit for the calculations below?
> - remove page_cgroup pointer from struct page allows us to reduce > static memory usage at boot by 8bytes/4096bytes if memory cgroup is disabled. > This reaches 96MB on my 48 GB box. I think this is big. > - pre-allocation of page_cgroup gives us following. > Pros. > - We are not necessary to be afraid of "failure of kmalloc" and > "goes down to memory reclaim at kmalloc" > This makes memory resource controller much simpler and robust. > - We can know what amount of kernel memory will be used for > LRU pages management. > Cons. > - All page_cgroups are allocated at boot. > This reaches 480MB on my 48GB box. > > But I think we can ignore "Cons.". If we use up memory, we'll use tons of > page_cgroup. Considering memory fragmentation caused by allocating a lots of > very small object, pre-allocation makes memcg better.
This looks like a good patch. I'll review and test it.
-- Balbir
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