Re: unusual scheduling performance

From: Andrew Morton (akpm@digeo.com)
Date: Mon Nov 18 2002 - 13:52:36 EST


Davide Libenzi wrote:
>
> On Mon, 18 Nov 2002, Andrew Morton wrote:
>
> > Dave Hansen wrote:
> > >
> > > ...
> > > rwsem_down_write_failed: 133 133
> >
> > Possible culprit.
> >
> > Please stick a dump_stack() in rwsem_down_write_failed(), and add the below.
> > Suggest you stick with 2.5.47 to diagnose this. The loss of kksymoops
> > is a pain.
> >
> >
> > fs/eventpoll.c | 2 ++
> > 1 files changed, 2 insertions(+)
> >
> > --- 25/fs/eventpoll.c~hey Mon Nov 18 10:13:40 2002
> > +++ 25-akpm/fs/eventpoll.c Mon Nov 18 10:14:01 2002
> > @@ -328,6 +328,8 @@ void eventpoll_release(struct file *file
> > if (list_empty(lsthead))
> > return;
> >
> > + printk("hey!\n");
> > +
>
> Andrew, if you don't use epoll there's no way you get there.

Yup. That was a random stab based on recently-added down_write()
calls.

However the down_write isn't there in 2.5.47 so that's a false
lead. We'll need that dump_stack() output.

Here's Dave's profile. ep_notify_file_close() makes a small appearance.
The change you made to 2.5.48 will wipe that out. Neat.

  0.058% 78 locks_remove_flock
  0.062% 82 page_cache_readahead
  0.062% 83 __generic_file_aio_read
  0.065% 86 file_move
  0.065% 87 dget_locked
  0.066% 88 proc_pid_stat
  0.067% 89 ep_notify_file_close
  0.068% 91 get_pid_list
  0.070% 93 update_atime
  0.079% 105 get_unused_fd
  0.085% 113 fget
  0.090% 120 dput
  0.091% 121 get_empty_filp
  0.097% 129 system_call
  0.100% 133 rwsem_down_write_failed
  0.124% 164 vfs_follow_link
  0.171% 227 file_read_actor
  0.182% 241 __fput
  0.221% 293 radix_tree_lookup
  0.232% 307 atomic_dec_and_lock
  0.250% 331 .text.lock.dec_and_lock
  0.282% 374 try_to_wake_up
  0.301% 398 kmap_atomic
  0.309% 409 kunmap_atomic
  0.326% 431 vfs_read
  0.364% 482 .text.lock.namei
  0.391% 518 __d_lookup
  0.537% 710 link_path_walk
  0.801% 1060 schedule
  1.396% 1846 do_generic_mapping_read
 25.275% 33416 poll_idle
 66.319% 87678 __copy_to_user
100.000% 132206 total
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