linux-kernel - Re: [DOC][for -mm] update Documentation/controller/memory.txt

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Message-ID: <475E1C2D.1030202@linux.vnet.ibm.com>
Date:	Tue, 11 Dec 2007 10:42:13 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"yamamoto@...inux.co.jp" <yamamoto@...inux.co.jp>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [DOC][for -mm] update Documentation/controller/memory.txt

KAMEZAWA Hiroyuki wrote:
> Balbir-san, could you review this update ?
> 
> --
> Documentation updates for memory controller.
> 
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> 
> Index: linux-2.6.24-rc4-mm1/Documentation/controllers/memory.txt
> ===================================================================
> --- linux-2.6.24-rc4-mm1.orig/Documentation/controllers/memory.txt
> +++ linux-2.6.24-rc4-mm1/Documentation/controllers/memory.txt
> @@ -9,8 +9,7 @@ d. Provides a double LRU: global memory 
>     global LRU; a cgroup on hitting a limit, reclaims from the per
>     cgroup LRU
> 
> -NOTE: Page Cache (unmapped) also includes Swap Cache pages as a subset
> -and will not be referred to explicitly in the rest of the documentation.
> +NOTE: Swap Cache (unmapped) is not accounted now.
> 
>  Benefits and Purpose of the memory controller
> 
> @@ -144,7 +143,7 @@ list.
>  The memory controller uses the following hierarchy
> 
>  1. zone->lru_lock is used for selecting pages to be isolated
> -2. mem->lru_lock protects the per cgroup LRU
> +2. mem->per_zone->lru_lock protects the per cgroup LRU (per zone)
>  3. lock_page_cgroup() is used to protect page->page_cgroup
> 
>  3. User Interface
> @@ -193,6 +192,15 @@ this file after a write to guarantee the
>  The memory.failcnt field gives the number of times that the cgroup limit was
>  exceeded.
> 
> +The memory.stat file gives accounting information. Now, the number of
> +caches, RSS and Active pages/Inactive pages are shown.
> +
> +The memory.force_empty gives an interface to drop *all* charges by force.
> +
> +# echo -n 1 > memory.force_empty
> +
> +will drop all charges in cgroup. Currently, this is maintained for test.
> +
>  4. Testing
> 
>  Balbir posted lmbench, AIM9, LTP and vmmstress results [10] and [11].
> @@ -222,11 +230,8 @@ reclaimed.
> 
>  A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a
>  cgroup might have some charge associated with it, even though all
> -tasks have migrated away from it. If some pages are still left, after following
> -the steps listed in sections 4.1 and 4.2, check the Swap Cache usage in
> -/proc/meminfo to see if the Swap Cache usage is showing up in the
> -cgroups memory.usage_in_bytes counter. A simple test of swapoff -a and
> -swapon -a should free any pending Swap Cache usage.
> +tasks have migrated away from it. Such charges are automatically dropped at
> +rmdir() if there are no tasks.
> 
>  4.4 Choosing what to account  -- Page Cache (unmapped) vs RSS (mapped)?
> 
> @@ -238,15 +243,11 @@ echo -n 1 > memory.control_type
>  5. TODO
> 
>  1. Add support for accounting huge pages (as a separate controller)
> -2. Improve the user interface to accept/display memory limits in KB or MB
> -   rather than pages (since page sizes can differ across platforms/machines).
> -3. Make cgroup lists per-zone
> -4. Make per-cgroup scanner reclaim not-shared pages first
> -5. Teach controller to account for shared-pages
> -6. Start reclamation when the limit is lowered
> -7. Start reclamation in the background when the limit is
> +2. Make per-cgroup scanner reclaim not-shared pages first
> +3. Teach controller to account for shared-pages
> +4. Start reclamation when the limit is lowered
> +5. Start reclamation in the background when the limit is
>     not yet hit but the usage is getting closer
> -8. Create per zone LRU lists per cgroup
> 

Looks very good to me!

Reviewed-by: Balbir Singh <balbir@...ux.vnet.ibm.com>

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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