Messages in this thread | | | Subject | Re: [MM] Make mm counters per cpu instead of atomic | From | "Zhang, Yanmin" <> | Date | Tue, 17 Nov 2009 17:34:25 +0800 |
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On Tue, 2009-11-17 at 15:31 +0800, Zhang, Yanmin wrote: > On Tue, 2009-11-17 at 14:48 +0800, Zhang, Yanmin wrote: > > On Wed, 2009-11-04 at 14:14 -0500, Christoph Lameter wrote: > > > From: Christoph Lameter <cl@linux-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@linux-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. > Changing it to below fixes the command hang issue. > > for_each_possible_cpu(cpu) { > struct mm_counter *m = per_cpu(mm->rss->readers, cpu); > > memset(m, 0, sizeof(struct mm_counter)); > }
Sorry. I was too optimistic and used another kernel to boot. The right change above should be: struct mm_counter *m = per_cpu_ptr(mm->rss, cpu);
Compiler doesn't report error/warning when I use any member.
With the change, command 'make oldconfig' and a boot command still hangs.
Yanmin
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