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Date: Tue, 17 Nov 2009 14:48:41 +0800 From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> To: Christoph Lameter <cl@...ux-foundation.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>, "hugh.dickins@...cali.co.uk" <hugh.dickins@...cali.co.uk>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, Tejun Heo <tj@...nel.org>, Andi Kleen <andi@...stfloor.org> Subject: Re: [MM] Make mm counters per cpu instead of atomic On Wed, 2009-11-04 at 14:14 -0500, Christoph Lameter wrote: > From: Christoph Lameter <cl@...ux-foundation.org> > Subject: Make mm counters per cpu > > Changing the mm counters to per cpu counters is possible after the introduction > of the generic per cpu operations (currently in percpu and -next). > > With that the contention on the counters in mm_struct can be avoided. The > USE_SPLIT_PTLOCKS case distinction can go away. Larger SMP systems do not > need to perform atomic updates to mm counters anymore. Various code paths > can be simplified since per cpu counter updates are fast and batching > of counter updates is no longer needed. > > One price to pay for these improvements is the need to scan over all percpu > counters when the actual count values are needed. > > Signed-off-by: Christoph Lameter <cl@...ux-foundation.org> > > --- > fs/proc/task_mmu.c | 14 +++++++++- > include/linux/mm_types.h | 16 ++++-------- > include/linux/sched.h | 61 ++++++++++++++++++++--------------------------- > kernel/fork.c | 25 ++++++++++++++----- > mm/filemap_xip.c | 2 - > mm/fremap.c | 2 - > mm/init-mm.c | 3 ++ > mm/memory.c | 20 +++++++-------- > mm/rmap.c | 10 +++---- > mm/swapfile.c | 2 - > 10 files changed, 84 insertions(+), 71 deletions(-) > > Index: linux-2.6/include/linux/mm_types.h > =================================================================== > --- linux-2.6.orig/include/linux/mm_types.h 2009-11-04 13:08:33.000000000 -0600 > +++ linux-2.6/include/linux/mm_types.h 2009-11-04 13:13:42.000000000 -0600 > @@ -24,11 +24,10 @@ struct address_space; > Index: linux-2.6/kernel/fork.c > =================================================================== > --- linux-2.6.orig/kernel/fork.c 2009-11-04 13:08:33.000000000 -0600 > +++ linux-2.6/kernel/fork.c 2009-11-04 13:14:19.000000000 -0600 > @@ -444,6 +444,8 @@ static void mm_init_aio(struct mm_struct > > static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) > { > + int cpu; > + > atomic_set(&mm->mm_users, 1); > atomic_set(&mm->mm_count, 1); > init_rwsem(&mm->mmap_sem); > @@ -452,8 +454,11 @@ static struct mm_struct * mm_init(struct > (current->mm->flags & MMF_INIT_MASK) : default_dump_filter; > mm->core_state = NULL; > mm->nr_ptes = 0; > - set_mm_counter(mm, file_rss, 0); > - set_mm_counter(mm, anon_rss, 0); > + for_each_possible_cpu(cpu) { > + struct mm_counter *m; > + > + memset(m, sizeof(struct mm_counter), 0); Above memset is wrong. 1) m isn't initiated; 2) It seems the 2nd and the 3rd parameters should be interchanged. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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