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    SubjectRe: [PATCH 22/24] HWPOISON: add memory cgroup filter
    On Thu, 3 Dec 2009 10:19:15 +0800
    Wu Fengguang <fengguang.wu@intel.com> wrote:

    > On Thu, Dec 03, 2009 at 09:52:29AM +0800, KAMEZAWA Hiroyuki wrote:
    > > On Wed, 2 Dec 2009 20:58:42 +0800
    > > Wu Fengguang <fengguang.wu@intel.com> wrote:
    > >
    > > > On Wed, Dec 02, 2009 at 08:44:46PM +0800, Andi Kleen wrote:
    > > > > >
    > > > > > +static int hwpoison_filter_task(struct page *p)
    > > > > > +{
    > > > >
    > > > > Can we make that ifdef instead of depends on ?
    > > >
    > > > Sure. Here is the updated patch.
    > > >
    > > > ---
    > > > HWPOISON: add memory cgroup filter
    > > >
    > > > The hwpoison test suite need to inject hwpoison to a collection of
    > > > selected task pages, and must not touch pages not owned by them and
    > > > thus kill important system processes such as init. (But it's OK to
    > > > mis-hwpoison free/unowned pages as well as shared clean pages.
    > > > Mis-hwpoison of shared dirty pages will kill all tasks, so the test
    > > > suite will target all or non of such tasks in the first place.)
    > > >
    > > > The memory cgroup serves this purpose well. We can put the target
    > > > processes under the control of a memory cgroup, and tell the hwpoison
    > > > injection code to only kill pages associated with some active memory
    > > > cgroup.
    > > >
    > > > The prerequisite for doing hwpoison stress tests with mem_cgroup is,
    > > > the mem_cgroup code tracks task pages _accurately_ (unless page is
    > > > locked). Which we believe is/should be true.
    > > >
    > > > The benifits are simplification of hwpoison injector code. Also the
    > > > mem_cgroup code will automatically be tested by hwpoison test cases.
    > > >
    > > > The alternative interfaces pin-pfn/unpin-pfn can also delegate the
    > > > (process and page flags) filtering functions reliably to user space.
    > > > However prototype implementation shows that this scheme adds more
    > > > complexity than we wanted.
    > > >
    > > > CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > > > CC: Hugh Dickins <hugh.dickins@tiscali.co.uk>
    > > > CC: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    > > > CC: Balbir Singh <balbir@linux.vnet.ibm.com>
    > > > CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > > > CC: Li Zefan <lizf@cn.fujitsu.com>
    > > > CC: Paul Menage <menage@google.com>
    > > > CC: Nick Piggin <npiggin@suse.de>
    > > > CC: Andi Kleen <andi@firstfloor.org>
    > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
    > > > ---
    > > > mm/Kconfig | 2 +-
    > > > mm/hwpoison-inject.c | 7 +++++++
    > > > mm/internal.h | 1 +
    > > > mm/memory-failure.c | 28 ++++++++++++++++++++++++++++
    > > > 4 files changed, 37 insertions(+), 1 deletion(-)
    > > >
    > > > --- linux-mm.orig/mm/memory-failure.c 2009-12-01 09:56:06.000000000 +0800
    > > > +++ linux-mm/mm/memory-failure.c 2009-12-02 20:56:55.000000000 +0800
    > > > @@ -96,6 +96,31 @@ static int hwpoison_filter_flags(struct
    > > > return -EINVAL;
    > > > }
    > > >
    > > > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
    > > > +u32 hwpoison_filter_memcg;
    > > > +static int hwpoison_filter_task(struct page *p)
    > > > +{
    > > > + struct mem_cgroup *mem;
    > > > + struct cgroup_subsys_state *css;
    > > > +
    > > > + if (!hwpoison_filter_memcg)
    > > > + return 0;
    > > > +
    > > > + mem = try_get_mem_cgroup_from_page(p);
    > > > + if (!mem)
    > > > + return -EINVAL;
    > > > +
    > > > + css = mem_cgroup_css(mem);
    > > > + if (!css)
    > > > + return -EINVAL;
    > >
    > > > +
    > > > + css_put(css);
    > > > + return 0;
    > > > +}
    > >
    > >
    > > Hmm..can you adds comment ? What does this function is for ?
    >
    > Good idea. How about this one?
    >
    > /*
    > * This allows stress tests to limit test scope to a collection of tasks
    > * by putting them under some memcg. This prevents killing unrelated/important
    > * processes such as /sbin/init. Note that the target task may share clean
    > * pages with init (eg. libc text), which is harmless. If the target task
    > * share _dirty_ pages with another task B, the test scheme must make sure B
    > * is also included in the memcg. At last, due to race conditions this filter
    > * can only guarantee that the page either belongs to the memcg tasks, or is
    > * a freed page.
    > */
    >
    Hmm. seems good but..by what means "avoiding killing /sbin/init" is done ?
    All process are under some memcg..

    If you have more patches to be usable the function above,
    I recommend you to post this with some real-use patches, in step by step.
    patch 19,20 is ok for me.

    Thanks,
    -Kame



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