On Thu, 7 Oct 2010 16:28:11 +0900
Daisuke Nishimura <nishim...@mxp.nes.nec.co.jp> wrote:
> On Thu, 7 Oct 2010 15:21:11 +0900
> KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com> wrote:
>
> > On Thu, 7 Oct 2010 11:17:43 +0900
> > KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com> wrote:
> >
> > > > hmm, if we'll do that, I think we need to do that under pte_lock in
> > > > mem_cgroup_move_charge_pte_range(). But, we can't do
> > > > wait_on_page_writeback()
> > > > under pte_lock, right? Or, we need re-organize current move-charge
> > > > implementation.
> > > >
> > > Nice catch. I think releaseing pte_lock() is okay. (and it should be
> > > released)
> > >
> > > IIUC, task's css_set() points to new cgroup when "move" is called. Then,
> > > it's not necessary to take pte_lock, I guess.
> > > (And taking pte_lock too long is not appreciated..)
> > >
> > > I'll write a sample patch today.
> > >
> > Here.
> Great!
>
> > ==
> > From: KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
> >
> > Now, at task migration among cgroup, memory cgroup scans page table and
> > moving
> > account if flags are properly set.
> >
> > The core code, mem_cgroup_move_charge_pte_range() does
> >
> > pte_offset_map_lock();
> > for all ptes in a page table:
> > 1. look into page table, find_and_get a page
> > 2. remove it from LRU.
> > 3. move charge.
> > 4. putback to LRU. put_page()
> > pte_offset_map_unlock();
> >
> > for pte entries on a 3rd(2nd) level page table.
> >
> > This pte_offset_map_lock seems a bit long. This patch modifies a rountine as
> >
> > pte_offset_map_lock()
> > for 32 pages:
> > find_and_get a page
> > record it
> > pte_offset_map_unlock()
> > for all recorded pages
> > isolate it from LRU.
> > move charge
> > putback to LRU
> > for all recorded pages
> > put_page()
> >
> > Note: newly-charged pages while we move account are charged to the new
> > group.
> >
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
> > ---
> > mm/memcontrol.c | 92
> > ++++++++++++++++++++++++++++++++++++--------------------
> > 1 file changed, 60 insertions(+), 32 deletions(-)
> >
> > Index: mmotm-0928/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0928.orig/mm/memcontrol.c
> > +++ mmotm-0928/mm/memcontrol.c
> > @@ -4475,17 +4475,22 @@ one_by_one:
> > *
> > * Called with pte lock held.
> > */
> > -union mc_target {
> > - struct page *page;
> > - swp_entry_t ent;
> > -};
> >
> > enum mc_target_type {
> > - MC_TARGET_NONE, /* not used */
> > + MC_TARGET_NONE, /* used as failure code(0) */
> > MC_TARGET_PAGE,
> > MC_TARGET_SWAP,
> > };
> >
> > +struct mc_target {
> > + enum mc_target_type type;
> > + union {
> > + struct page *page;
> > + swp_entry_t ent;
> > + } val;
> > +};
> > +
> > +
> > static struct page *mc_handle_present_pte(struct vm_area_struct *vma,
> > unsigned long addr, pte_t ptent)
> > {
> > @@ -4561,7 +4566,7 @@ static struct page *mc_handle_file_pte(s
> > }
> >
> > static int is_target_pte_for_mc(struct vm_area_struct *vma,
> > - unsigned long addr, pte_t ptent, union mc_target *target)
> > + unsigned long addr, pte_t ptent, struct mc_target *target)
> > {
> > struct page *page = NULL;
> > struct page_cgroup *pc;
> > @@ -4587,7 +4592,7 @@ static int is_target_pte_for_mc(struct v
> > if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
> > ret = MC_TARGET_PAGE;
> > if (target)
> > - target->page = page;
> > + target->val.page = page;
> > }
> > if (!ret || !target)
> > put_page(page);
> > @@ -4597,8 +4602,10 @@ static int is_target_pte_for_mc(struct v
> > css_id(&mc.from->css) == lookup_swap_cgroup(ent)) {
> > ret = MC_TARGET_SWAP;
> > if (target)
> > - target->ent = ent;
> > + target->val.ent = ent;
> > }
> > + if (target)
> > + target->type = ret;
> > return ret;
> > }
> >
> > @@ -4751,6 +4758,9 @@ static void mem_cgroup_cancel_attach(str
> > mem_cgroup_clear_mc();
> > }
> >
> > +
> > +#define MC_MOVE_ONCE (32)
> > +
> > static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
> > unsigned long addr, unsigned long end,
> > struct mm_walk *walk)
> > @@ -4759,26 +4769,47 @@ static int mem_cgroup_move_charge_pte_ra
> > struct vm_area_struct *vma = walk->private;
> > pte_t *pte;
> > spinlock_t *ptl;
> > + struct mc_target *target;
> > + int index, num;
> > +
> > + target = kzalloc(sizeof(struct mc_target) *MC_MOVE_ONCE, GFP_KERNEL);
> hmm? I can't see it freed anywhere.
>
leaked..
> Considering you reset target[]->type to MC_TARGET_NONE, do you intended to
> reuse targe[] while walking the page table ?
yes.
> If so, how about adding a new member(struct mc_target *targe) to
> move_charge_struct,
> and allocate/free it at mem_cgroup_move_charge() ?
>
Hmm, sounds nice.
I'll do.
Thanks,
-Kame
> Thanks,
> Daisuke Nishimura.
>
> > + if (!target)
> > + return -ENOMEM;
> >
> > retry:
> > pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
> > - for (; addr != end; addr += PAGE_SIZE) {
> > + for (num = 0; num < MC_MOVE_ONCE && addr != end; addr += PAGE_SIZE) {
> > pte_t ptent = *(pte++);
> > - union mc_target target;
> > - int type;
> > + ret = is_target_pte_for_mc(vma, addr, ptent, &target[num]);
> > + if (!ret)
> > + continue;
> > + target[num++].type = ret;
> > + }
> > + pte_unmap_unlock(pte - 1, ptl);
> > + cond_resched();
> > +
> > + ret = 0;
> > + index = 0;
> > + do {
> > + struct mc_target *mt;
> > struct page *page;
> > struct page_cgroup *pc;
> > swp_entry_t ent;
> >
> > - if (!mc.precharge)
> > - break;
> > + if (!mc.precharge) {
> > + ret = mem_cgroup_do_precharge(1);
> > + if (ret)
> > + goto out;
> > + continue;
> > + }
> > +
> > + mt = &target[index++];
> >
> > - type = is_target_pte_for_mc(vma, addr, ptent, &target);
> > - switch (type) {
> > + switch (mt->type) {
> > case MC_TARGET_PAGE:
> > - page = target.page;
> > + page = mt->val.page;
> > if (isolate_lru_page(page))
> > - goto put;
> > + break;
> > pc = lookup_page_cgroup(page);
> > if (!mem_cgroup_move_account(pc,
> > mc.from, mc.to, false)) {
> > @@ -4787,11 +4818,9 @@ retry:
> > mc.moved_charge++;
> > }
> > putback_lru_page(page);
> > -put: /* is_target_pte_for_mc() gets the page */
> > - put_page(page);
> > break;
> > case MC_TARGET_SWAP:
> > - ent = target.ent;
> > + ent = mt->val.ent;
> > if (!mem_cgroup_move_swap_account(ent,
> > mc.from, mc.to, false)) {
> > mc.precharge--;
> > @@ -4802,21 +4831,20 @@ put: /*
> > is_target_pte_for_mc() gets th
> > default:
> > break;
> > }
> > + } while (index < num);
> > +out:
> > + for (index = 0; index < num; index++) {
> > + if (target[index].type == MC_TARGET_PAGE)
> > + put_page(target[index].val.page);
> > + target[index].type = MC_TARGET_NONE;
> > }
> > - pte_unmap_unlock(pte - 1, ptl);
> > +
> > + if (ret)
> > + return ret;
> > cond_resched();
> >
> > - if (addr != end) {
> > - /*
> > - * We have consumed all precharges we got in can_attach().
> > - * We try charge one by one, but don't do any additional
> > - * charges to mc.to if we have failed in charge once in attach()
> > - * phase.
> > - */
> > - ret = mem_cgroup_do_precharge(1);
> > - if (!ret)
> > - goto retry;
> > - }
> > + if (addr != end)
> > + goto retry;
> >
> > return ret;
> > }
> >
>
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