Messages in this thread |  | | | Date | Tue, 02 Sep 2008 13:05:17 +0530 | | From | Balbir Singh <> | | Subject | Re: [RFC][PATCH] Remove cgroup member from struct page |
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Peter Zijlstra wrote: > On Mon, 2008-09-01 at 14:47 +0530, Balbir Singh wrote: >> Pavel Emelyanov wrote: >>> Balbir Singh wrote: >>>> This is a rewrite of a patch I had written long back to remove struct page >>>> (I shared the patches with Kamezawa, but never posted them anywhere else). >>>> I spent the weekend, cleaning them up for 2.6.27-rc5-mmotm (29 Aug 2008). >>>> >>>> I've tested the patches on an x86_64 box, I've run a simple test running >>>> under the memory control group and the same test running concurrently under >>>> two different groups (and creating pressure within their groups). I've also >>>> compiled the patch with CGROUP_MEM_RES_CTLR turned off. >>>> >>>> Advantages of the patch >>>> >>>> 1. It removes the extra pointer in struct page >>>> >>>> Disadvantages >>>> >>>> 1. It adds an additional lock structure to struct page_cgroup >>>> 2. Radix tree lookup is not an O(1) operation, once the page is known >>>> getting to the page_cgroup (pc) is a little more expensive now. >>> And besides, we also have a global lock, that protects even lookup >>> from this structure. Won't this affect us too much on bug-smp nodes? >> Sorry, not sure I understand. The lookup is done under RCU. Updates are done >> using the global lock. It should not be hard to make the radix tree per node >> later (as an iterative refinement). > > Or you could have a look at the concurrent radix tree, esp for dense > trees it can save a lot on lock bouncing. > > Latest code available at: > > http://programming.kicks-ass.net/kernel-patches/concurrent-pagecache/27-rc3/
I'll try them later. I see a lot of slab allocations/frees (expected). I am trying to experiment with alternatives to reduce them.
-- Balbir
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