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Message-Id: <20090722.183011.226792119.ryov@valinux.co.jp>
Date: Wed, 22 Jul 2009 18:30:11 +0900 (JST)
From: Ryo Tsuruta <ryov@...inux.co.jp>
To: kamezawa.hiroyu@...fujitsu.com
Cc: balbir@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
dm-devel@...hat.com, containers@...ts.linux-foundation.org,
virtualization@...ts.linux-foundation.org,
xen-devel@...ts.xensource.com, agk@...hat.com
Subject: Re: [PATCH 3/9] blkio-cgroup-v9: The new page_cgroup framework
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> On Wed, 22 Jul 2009 17:28:43 +0900 (JST)
> Ryo Tsuruta <ryov@...inux.co.jp> wrote:
> > > But, following is more straightforward. (and what you do is not different
> > > from this.)
> > > ==
> > > struct page {
> > > .....
> > > #ifdef CONFIG_BLOCKIO_CGROUP
> > > void *blockio_cgroup;
> > > #endif
> > > }
> > > ==
> >
> > This increases the size of struct page. Could I get a consensus on
> > this approach?
> >
> Just God knows ;)
>
> To be honest, what I expected in these days for people of blockio cgroup is like
> following for getting room for themselves.
>
> I'm now thinking to do this by myself and offer a room for you because
> terrible bugs have been gone now and I have time.
It is very nice for blkio-cgroup, it can make blkio-cgroup simple and
more faster to track down the owner of an I/O request.
Thanks,
Ryo Tsuruta
> Balbir, if you have no concerns, I'll clean up and send this to mmotm.
> (maybe softlimit accesses pc->page and I have to update this.)
>
> Note: This is _not_ tested at all.
>
> Thanks,
> -Kame
> ==
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> page cgroup has pointer to memmap it stands for.
> But, page_cgroup->page is not accessed in fast path and not necessary
> and not modified. Then, it's not to be maintained as pointer.
>
> This patch removes "page" from page_cgroup and add
> page_cgroup_to_page() function. This uses some amount of FLAGS bit
> as struct page does.
> As side effect, nid, zid can be obtaind from page_cgroup itself.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
> include/linux/page_cgroup.h | 19 ++++++++++++++++---
> mm/page_cgroup.c | 42 ++++++++++++++++++++++++++++++++----------
> 2 files changed, 48 insertions(+), 13 deletions(-)
>
> Index: mmotm-2.6.31-Jul16/include/linux/page_cgroup.h
> ===================================================================
> --- mmotm-2.6.31-Jul16.orig/include/linux/page_cgroup.h
> +++ mmotm-2.6.31-Jul16/include/linux/page_cgroup.h
> @@ -13,7 +13,7 @@
> struct page_cgroup {
> unsigned long flags;
> struct mem_cgroup *mem_cgroup;
> - struct page *page;
> + /* block io tracking will use extra unsigned long bytes */
> struct list_head lru; /* per cgroup LRU list */
> };
>
> @@ -32,7 +32,12 @@ static inline void __init page_cgroup_in
> #endif
>
> struct page_cgroup *lookup_page_cgroup(struct page *page);
> +struct page *page_cgroup_to_page(struct page_cgroup *page);
>
> +/*
> + * TOP MOST (NODE_SHIFT+ZONE_SHIFT or SECTION_SHIFT bits of "flags" are used
> + * for detecting pfn as struct page does.
> + */
> enum {
> /* flags for mem_cgroup */
> PCG_LOCK, /* page cgroup is locked */
> @@ -71,14 +76,22 @@ CLEARPCGFLAG(AcctLRU, ACCT_LRU)
> TESTPCGFLAG(AcctLRU, ACCT_LRU)
> TESTCLEARPCGFLAG(AcctLRU, ACCT_LRU)
>
> +#ifdef NODE_NOT_IN_PAGE_FLAGS
> static inline int page_cgroup_nid(struct page_cgroup *pc)
> {
> - return page_to_nid(pc->page);
> + struct page *page= page_cgroup_to_page(pc);
> + return page_to_nid(page);
> }
> +#else
> +static inline int page_cgroup_nid(struct page_cgroup *pc)
> +{
> + return (pc->flags >> NODES_PGSHIFT) & NODES_MASK;
> +}
> +#endif
>
> static inline enum zone_type page_cgroup_zid(struct page_cgroup *pc)
> {
> - return page_zonenum(pc->page);
> + return (pc->flags >> ZONEID_PGSHIFT) & ZONEID_MASK;
> }
>
> static inline void lock_page_cgroup(struct page_cgroup *pc)
> Index: mmotm-2.6.31-Jul16/mm/page_cgroup.c
> ===================================================================
> --- mmotm-2.6.31-Jul16.orig/mm/page_cgroup.c
> +++ mmotm-2.6.31-Jul16/mm/page_cgroup.c
> @@ -13,9 +13,12 @@
> static void __meminit
> __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
> {
> - pc->flags = 0;
> + unsigned long flags;
> +
> pc->mem_cgroup = NULL;
> - pc->page = pfn_to_page(pfn);
> + /* Copy NODE/ZONE/SECTION information from struct page */
> + flags = pfn_to_page(pfn)->flags;
> + pc->flags = flags & ~((1 << __NR_PAGEFLAGS) - 1);
> INIT_LIST_HEAD(&pc->lru);
> }
> static unsigned long total_usage;
> @@ -42,6 +45,18 @@ struct page_cgroup *lookup_page_cgroup(s
> return base + offset;
> }
>
> +struct page *page_cgroup_to_page(struct page_cgroup *pc)
> +{
> + int nid = (page->flags >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
> + unsigned long pfn, offset;
> +
> + offset = pc - NODE_DATA(nid)->node_page_cgroup
> + pfn = NODE_DATA(nid)->node_start_pfn + offset;
> +
> + return pfn_to_page(pfn);
> +}
> +
> +
> static int __init alloc_node_page_cgroup(int nid)
> {
> struct page_cgroup *base, *pc;
> @@ -104,6 +119,18 @@ struct page_cgroup *lookup_page_cgroup(s
> return section->page_cgroup + pfn;
> }
>
> +struct page *page_cgroup_to_page(struct page_cgroup *pc)
> +{
> + unsigned long pfn, sectionid;
> + struct mem_section *section;
> +
> + sectionid = (pc->flags >> SECTIONS_PGSHIFT) & SECTIONS_MASK;
> + section = __nr_to_section(sectionid);
> +
> + pfn = pc - section->page_cgroup;
> + return pfn_to_page(pfn);
> +}
> +
> /* __alloc_bootmem...() is protected by !slab_available() */
> static int __init_refok init_section_page_cgroup(unsigned long pfn)
> {
> @@ -128,15 +155,10 @@ static int __init_refok init_section_pag
> }
> } else {
> /*
> - * We don't have to allocate page_cgroup again, but
> - * address of memmap may be changed. So, we have to initialize
> - * again.
> + * We don't have to allocate page_cgroup again, and we don't
> + * take care of address of memmap.
> */
> - base = section->page_cgroup + pfn;
> - table_size = 0;
> - /* check address of memmap is changed or not. */
> - if (base->page == pfn_to_page(pfn))
> - return 0;
> + return 0;
> }
>
> if (!base) {
>
> --
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