Re: [RFC][PATCH 0/5] Signal scalability series

Oleg Nesterov
2011-09-30T18:58:58Z

On 09/30, Oleg Nesterov wrote:
>
> On 09/30, Matt Fleming wrote:
> >
> > However, it's a good first step and
> > hopefully by keeping it relatively simple it'll make it easier to
> > review.
>
> Cough. I'll try to read this series next week, but currently I feel
> I will never able to understand this code. It surely compliacates
> things a lot.
>
> But. All I can do is to _try_ to check this series from the correctness
> pov. I can't believe (at least at first glance) this worth the trouble,
> but otoh I won't argue unless I'll find the bugs.
>
> > arch/ia64/kernel/signal.c | 4 +-
> > drivers/block/nbd.c | 2 +-
> > drivers/usb/gadget/f_mass_storage.c | 2 +-
> > drivers/usb/gadget/file_storage.c | 2 +-
> > fs/autofs4/waitq.c | 5 +-
> > fs/exec.c | 17 +-
> > fs/jffs2/background.c | 2 +-
> > fs/ncpfs/sock.c | 2 +
> > fs/proc/array.c | 2 +
> > fs/signalfd.c | 11 +-
> > include/linux/init_task.h | 4 +
> > include/linux/sched.h | 23 +-
> > kernel/exit.c | 29 +-
> > kernel/fork.c | 4 +
> > kernel/freezer.c | 10 +-
> > kernel/kmod.c | 8 +-
> > kernel/posix-timers.c | 5 +-
> > kernel/ptrace.c | 68 ++--
> > kernel/signal.c | 737 +++++++++++++++++++++++++++--------
> > net/9p/client.c | 6 +-
> > net/sunrpc/svc.c | 3 -
> > security/selinux/hooks.c | 11 +-
> > 22 files changed, 677 insertions(+), 280 deletions(-)
>
> And, this patch adds 4 new locks:
>
> sighand_struct->action_lock
>
> signal_struct->ctrl_lock
> signal_struct->shared_siglock
>
> task_struct->siglock
>
> Nice ;) For what? This should be justified, imho.

Yes. I did the quick and dirty check (under kvm),

Before this series:

[tst@myhost ~]$ time perl -wle '$SIG{HUP}=sub{}; kill HUP, $$ for 1..100_000'

real 0m2.451s
user 0m0.350s
sys 0m2.097s
[tst@myhost ~]$ time perl -wle '$SIG{HUP}=sub{}; kill HUP, $$ for 1..100_000'

real 0m2.475s
user 0m0.357s
sys 0m2.117s
[tst@myhost ~]$ time perl -wle '$SIG{HUP}=sub{}; kill HUP, $$ for 1..100_000'

real 0m2.443s
user 0m0.330s
sys 0m2.113s

After:

tst@myhost ~]$ time perl -wle '$SIG{HUP}=sub{}; kill HUP, $$ for 1..100_000'

real 0m3.194s
user 0m0.283s
sys 0m2.910s
[tst@myhost ~]$ time perl -wle '$SIG{HUP}=sub{}; kill HUP, $$ for 1..100_000'

real 0m3.212s
user 0m0.357s
sys 0m2.853s
[tst@myhost ~]$ time perl -wle '$SIG{HUP}=sub{}; kill HUP, $$ for 1..100_000'

real 0m3.196s
user 0m0.350s
sys 0m2.846s

Doesn't like very good (may be only under kvm?). In fact I am really
surprised, I didn't expect the difference will be that noticeable.

Yes, yes, I understand that your goal is scalability, but still.

Oleg.