* [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
@ 2013-05-22 5:50 Simon Horman
2013-05-22 5:50 ` [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper Simon Horman
` (2 more replies)
0 siblings, 3 replies; 11+ messages in thread
From: Simon Horman @ 2013-05-22 5:50 UTC (permalink / raw)
To: Eric Dumazet, Julian Anastasov, Ingo Molnar, Peter Zijlstra,
Paul E. McKenney
Cc: lvs-devel, netdev, netfilter-devel, linux-kernel,
Pablo Neira Ayuso, Dipankar Sarma, Simon Horman
Add a helper that for use in loops which read data protected by RCU and
may have a large number of iterations. Such an example is dumping the list
of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
This series also updates IPVS to use the helper.
Simon Horman (2):
sched: add cond_resched_rcu() helper
ipvs: use cond_resched_rcu() helper when walking connections
include/linux/sched.h | 9 +++++++++
net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
2 files changed, 17 insertions(+), 15 deletions(-)
--
1.8.2.1
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper
2013-05-22 5:50 [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Simon Horman
@ 2013-05-22 5:50 ` Simon Horman
2013-05-23 11:30 ` Pablo Neira Ayuso
2013-05-22 5:50 ` [PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections Simon Horman
2013-05-22 7:54 ` [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Peter Zijlstra
2 siblings, 1 reply; 11+ messages in thread
From: Simon Horman @ 2013-05-22 5:50 UTC (permalink / raw)
To: Eric Dumazet, Julian Anastasov, Ingo Molnar, Peter Zijlstra,
Paul E. McKenney
Cc: lvs-devel, netdev, netfilter-devel, linux-kernel,
Pablo Neira Ayuso, Dipankar Sarma, Simon Horman
This is intended for use in loops which read data protected by RCU and may
have a large number of iterations. Such an example is dumping the list of
connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
The benefits are for CONFIG_PREEMPT_RCU=y where we save CPU cycles
by moving rcu_read_lock and rcu_read_unlock out of large loops
but still allowing the current task to be preempted after every
loop iteration for the CONFIG_PREEMPT_RCU=n case.
The call to cond_resched() is not needed when CONFIG_PREEMPT_RCU=y.
Thanks to Paul E. McKenney for explaining this and for the
final version that checks the context with CONFIG_DEBUG_ATOMIC_SLEEP=y
for all possible configurations.
The function can be empty in the CONFIG_PREEMPT_RCU case,
rcu_read_lock and rcu_read_unlock are not needed in this case
because the task can be preempted on indication from scheduler.
Thanks to Peter Zijlstra for catching this and for his help
in trying a solution that changes __might_sleep.
Initial cond_resched_rcu_lock() function suggested by Eric Dumazet.
Tested-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
---
include/linux/sched.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e692a02..2080446 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2608,6 +2608,15 @@ extern int __cond_resched_softirq(void);
__cond_resched_softirq(); \
})
+static inline void cond_resched_rcu(void)
+{
+#if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU)
+ rcu_read_unlock();
+ cond_resched();
+ rcu_read_lock();
+#endif
+}
+
/*
* Does a critical section need to be broken due to another
* task waiting?: (technically does not depend on CONFIG_PREEMPT,
--
1.8.2.1
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections
2013-05-22 5:50 [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Simon Horman
2013-05-22 5:50 ` [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper Simon Horman
@ 2013-05-22 5:50 ` Simon Horman
2013-05-23 11:30 ` Pablo Neira Ayuso
2013-05-22 7:54 ` [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Peter Zijlstra
2 siblings, 1 reply; 11+ messages in thread
From: Simon Horman @ 2013-05-22 5:50 UTC (permalink / raw)
To: Eric Dumazet, Julian Anastasov, Ingo Molnar, Peter Zijlstra,
Paul E. McKenney
Cc: lvs-devel, netdev, netfilter-devel, linux-kernel,
Pablo Neira Ayuso, Dipankar Sarma, Simon Horman
This avoids the situation where walking of a large number of connections
may prevent scheduling for a long time while also avoiding excessive
calls to rcu_read_unlock() and rcu_read_lock().
Note that in the case of !CONFIG_PREEMPT_RCU this will
add a call to cond_resched().
[ja@ssi.bg: add cond_resched_rcu to more places]
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
---
net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
1 file changed, 8 insertions(+), 15 deletions(-)
diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index a083bda..c8c52a9 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -975,8 +975,7 @@ static void *ip_vs_conn_array(struct seq_file *seq, loff_t pos)
return cp;
}
}
- rcu_read_unlock();
- rcu_read_lock();
+ cond_resched_rcu();
}
return NULL;
@@ -1015,8 +1014,7 @@ static void *ip_vs_conn_seq_next(struct seq_file *seq, void *v, loff_t *pos)
iter->l = &ip_vs_conn_tab[idx];
return cp;
}
- rcu_read_unlock();
- rcu_read_lock();
+ cond_resched_rcu();
}
iter->l = NULL;
return NULL;
@@ -1206,17 +1204,13 @@ void ip_vs_random_dropentry(struct net *net)
int idx;
struct ip_vs_conn *cp, *cp_c;
+ rcu_read_lock();
/*
* Randomly scan 1/32 of the whole table every second
*/
for (idx = 0; idx < (ip_vs_conn_tab_size>>5); idx++) {
unsigned int hash = net_random() & ip_vs_conn_tab_mask;
- /*
- * Lock is actually needed in this loop.
- */
- rcu_read_lock();
-
hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[hash], c_list) {
if (cp->flags & IP_VS_CONN_F_TEMPLATE)
/* connection template */
@@ -1252,8 +1246,9 @@ void ip_vs_random_dropentry(struct net *net)
__ip_vs_conn_put(cp);
}
}
- rcu_read_unlock();
+ cond_resched_rcu();
}
+ rcu_read_unlock();
}
@@ -1267,11 +1262,8 @@ static void ip_vs_conn_flush(struct net *net)
struct netns_ipvs *ipvs = net_ipvs(net);
flush_again:
+ rcu_read_lock();
for (idx = 0; idx < ip_vs_conn_tab_size; idx++) {
- /*
- * Lock is actually needed in this loop.
- */
- rcu_read_lock();
hlist_for_each_entry_rcu(cp, &ip_vs_conn_tab[idx], c_list) {
if (!ip_vs_conn_net_eq(cp, net))
@@ -1286,8 +1278,9 @@ flush_again:
__ip_vs_conn_put(cp);
}
}
- rcu_read_unlock();
+ cond_resched_rcu();
}
+ rcu_read_unlock();
/* the counter may be not NULL, because maybe some conn entries
are run by slow timer handler or unhashed but still referred */
--
1.8.2.1
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
2013-05-22 5:50 [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Simon Horman
2013-05-22 5:50 ` [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper Simon Horman
2013-05-22 5:50 ` [PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections Simon Horman
@ 2013-05-22 7:54 ` Peter Zijlstra
2013-05-22 8:31 ` David Miller
2 siblings, 1 reply; 11+ messages in thread
From: Peter Zijlstra @ 2013-05-22 7:54 UTC (permalink / raw)
To: Simon Horman
Cc: Eric Dumazet, Julian Anastasov, Ingo Molnar, Paul E. McKenney,
lvs-devel, netdev, netfilter-devel, linux-kernel,
Pablo Neira Ayuso, Dipankar Sarma
On Wed, May 22, 2013 at 02:50:30PM +0900, Simon Horman wrote:
> Add a helper that for use in loops which read data protected by RCU and
> may have a large number of iterations. Such an example is dumping the list
> of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
>
> This series also updates IPVS to use the helper.
>
> Simon Horman (2):
> sched: add cond_resched_rcu() helper
> ipvs: use cond_resched_rcu() helper when walking connections
>
> include/linux/sched.h | 9 +++++++++
> net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
> 2 files changed, 17 insertions(+), 15 deletions(-)
Acked-by: Peter Zijlstra <peterz@infradead.org>
How do you want to go about merging this? Do you want to route it
through the net tree or through -tip?
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
2013-05-22 7:54 ` [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Peter Zijlstra
@ 2013-05-22 8:31 ` David Miller
2013-05-22 9:00 ` Peter Zijlstra
` (2 more replies)
0 siblings, 3 replies; 11+ messages in thread
From: David Miller @ 2013-05-22 8:31 UTC (permalink / raw)
To: peterz
Cc: horms, eric.dumazet, ja, mingo, paulmck, lvs-devel, netdev,
netfilter-devel, linux-kernel, pablo, dipankar
From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 22 May 2013 09:54:38 +0200
> On Wed, May 22, 2013 at 02:50:30PM +0900, Simon Horman wrote:
>> Add a helper that for use in loops which read data protected by RCU and
>> may have a large number of iterations. Such an example is dumping the list
>> of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
>>
>> This series also updates IPVS to use the helper.
>>
>> Simon Horman (2):
>> sched: add cond_resched_rcu() helper
>> ipvs: use cond_resched_rcu() helper when walking connections
>>
>> include/linux/sched.h | 9 +++++++++
>> net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
>> 2 files changed, 17 insertions(+), 15 deletions(-)
>
> Acked-by: Peter Zijlstra <peterz@infradead.org>
>
> How do you want to go about merging this? Do you want to route it
> through the net tree or through -tip?
I think we can have Pablo merge it into his netfilter tree.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
2013-05-22 8:31 ` David Miller
@ 2013-05-22 9:00 ` Peter Zijlstra
2013-05-23 1:11 ` Simon Horman
2013-05-23 11:31 ` Pablo Neira Ayuso
2013-05-28 8:51 ` Ingo Molnar
2 siblings, 1 reply; 11+ messages in thread
From: Peter Zijlstra @ 2013-05-22 9:00 UTC (permalink / raw)
To: David Miller
Cc: horms, eric.dumazet, ja, mingo, paulmck, lvs-devel, netdev,
netfilter-devel, linux-kernel, pablo, dipankar
On Wed, May 22, 2013 at 01:31:08AM -0700, David Miller wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed, 22 May 2013 09:54:38 +0200
>
> > On Wed, May 22, 2013 at 02:50:30PM +0900, Simon Horman wrote:
> >> Add a helper that for use in loops which read data protected by RCU and
> >> may have a large number of iterations. Such an example is dumping the list
> >> of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
> >>
> >> This series also updates IPVS to use the helper.
> >>
> >> Simon Horman (2):
> >> sched: add cond_resched_rcu() helper
> >> ipvs: use cond_resched_rcu() helper when walking connections
> >>
> >> include/linux/sched.h | 9 +++++++++
> >> net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
> >> 2 files changed, 17 insertions(+), 15 deletions(-)
> >
> > Acked-by: Peter Zijlstra <peterz@infradead.org>
> >
> > How do you want to go about merging this? Do you want to route it
> > through the net tree or through -tip?
>
> I think we can have Pablo merge it into his netfilter tree.
Works for me. Thanks!
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
2013-05-22 9:00 ` Peter Zijlstra
@ 2013-05-23 1:11 ` Simon Horman
0 siblings, 0 replies; 11+ messages in thread
From: Simon Horman @ 2013-05-23 1:11 UTC (permalink / raw)
To: Peter Zijlstra
Cc: David Miller, eric.dumazet, ja, mingo, paulmck, lvs-devel,
netdev, netfilter-devel, linux-kernel, pablo, dipankar
On Wed, May 22, 2013 at 11:00:51AM +0200, Peter Zijlstra wrote:
> On Wed, May 22, 2013 at 01:31:08AM -0700, David Miller wrote:
> > From: Peter Zijlstra <peterz@infradead.org>
> > Date: Wed, 22 May 2013 09:54:38 +0200
> >
> > > On Wed, May 22, 2013 at 02:50:30PM +0900, Simon Horman wrote:
> > >> Add a helper that for use in loops which read data protected by RCU and
> > >> may have a large number of iterations. Such an example is dumping the list
> > >> of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
> > >>
> > >> This series also updates IPVS to use the helper.
> > >>
> > >> Simon Horman (2):
> > >> sched: add cond_resched_rcu() helper
> > >> ipvs: use cond_resched_rcu() helper when walking connections
> > >>
> > >> include/linux/sched.h | 9 +++++++++
> > >> net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
> > >> 2 files changed, 17 insertions(+), 15 deletions(-)
> > >
> > > Acked-by: Peter Zijlstra <peterz@infradead.org>
> > >
> > > How do you want to go about merging this? Do you want to route it
> > > through the net tree or through -tip?
> >
> > I think we can have Pablo merge it into his netfilter tree.
>
> Works for me. Thanks!
Thanks, I will queue it up in ipvs-next and pass it to Pablo from there.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper
2013-05-22 5:50 ` [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper Simon Horman
@ 2013-05-23 11:30 ` Pablo Neira Ayuso
0 siblings, 0 replies; 11+ messages in thread
From: Pablo Neira Ayuso @ 2013-05-23 11:30 UTC (permalink / raw)
To: Simon Horman
Cc: Eric Dumazet, Julian Anastasov, Ingo Molnar, Peter Zijlstra,
Paul E. McKenney, lvs-devel, netdev, netfilter-devel,
linux-kernel, Dipankar Sarma
On Wed, May 22, 2013 at 02:50:31PM +0900, Simon Horman wrote:
> This is intended for use in loops which read data protected by RCU and may
> have a large number of iterations. Such an example is dumping the list of
> connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
>
> The benefits are for CONFIG_PREEMPT_RCU=y where we save CPU cycles
> by moving rcu_read_lock and rcu_read_unlock out of large loops
> but still allowing the current task to be preempted after every
> loop iteration for the CONFIG_PREEMPT_RCU=n case.
>
> The call to cond_resched() is not needed when CONFIG_PREEMPT_RCU=y.
> Thanks to Paul E. McKenney for explaining this and for the
> final version that checks the context with CONFIG_DEBUG_ATOMIC_SLEEP=y
> for all possible configurations.
>
> The function can be empty in the CONFIG_PREEMPT_RCU case,
> rcu_read_lock and rcu_read_unlock are not needed in this case
> because the task can be preempted on indication from scheduler.
> Thanks to Peter Zijlstra for catching this and for his help
> in trying a solution that changes __might_sleep.
>
> Initial cond_resched_rcu_lock() function suggested by Eric Dumazet.
Applied, thanks.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections
2013-05-22 5:50 ` [PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections Simon Horman
@ 2013-05-23 11:30 ` Pablo Neira Ayuso
0 siblings, 0 replies; 11+ messages in thread
From: Pablo Neira Ayuso @ 2013-05-23 11:30 UTC (permalink / raw)
To: Simon Horman
Cc: Eric Dumazet, Julian Anastasov, Ingo Molnar, Peter Zijlstra,
Paul E. McKenney, lvs-devel, netdev, netfilter-devel,
linux-kernel, Dipankar Sarma
On Wed, May 22, 2013 at 02:50:32PM +0900, Simon Horman wrote:
> This avoids the situation where walking of a large number of connections
> may prevent scheduling for a long time while also avoiding excessive
> calls to rcu_read_unlock() and rcu_read_lock().
>
> Note that in the case of !CONFIG_PREEMPT_RCU this will
> add a call to cond_resched().
Applied, thanks.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
2013-05-22 8:31 ` David Miller
2013-05-22 9:00 ` Peter Zijlstra
@ 2013-05-23 11:31 ` Pablo Neira Ayuso
2013-05-28 8:51 ` Ingo Molnar
2 siblings, 0 replies; 11+ messages in thread
From: Pablo Neira Ayuso @ 2013-05-23 11:31 UTC (permalink / raw)
To: David Miller
Cc: peterz, horms, eric.dumazet, ja, mingo, paulmck, lvs-devel,
netdev, netfilter-devel, linux-kernel, dipankar
On Wed, May 22, 2013 at 01:31:08AM -0700, David Miller wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed, 22 May 2013 09:54:38 +0200
>
> > On Wed, May 22, 2013 at 02:50:30PM +0900, Simon Horman wrote:
> >> Add a helper that for use in loops which read data protected by RCU and
> >> may have a large number of iterations. Such an example is dumping the list
> >> of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
> >>
> >> This series also updates IPVS to use the helper.
> >>
> >> Simon Horman (2):
> >> sched: add cond_resched_rcu() helper
> >> ipvs: use cond_resched_rcu() helper when walking connections
> >>
> >> include/linux/sched.h | 9 +++++++++
> >> net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
> >> 2 files changed, 17 insertions(+), 15 deletions(-)
> >
> > Acked-by: Peter Zijlstra <peterz@infradead.org>
> >
> > How do you want to go about merging this? Do you want to route it
> > through the net tree or through -tip?
>
> I think we can have Pablo merge it into his netfilter tree.
I did so. Thanks David.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper
2013-05-22 8:31 ` David Miller
2013-05-22 9:00 ` Peter Zijlstra
2013-05-23 11:31 ` Pablo Neira Ayuso
@ 2013-05-28 8:51 ` Ingo Molnar
2 siblings, 0 replies; 11+ messages in thread
From: Ingo Molnar @ 2013-05-28 8:51 UTC (permalink / raw)
To: David Miller
Cc: peterz, horms, eric.dumazet, ja, mingo, paulmck, lvs-devel,
netdev, netfilter-devel, linux-kernel, pablo, dipankar
* David Miller <davem@davemloft.net> wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Wed, 22 May 2013 09:54:38 +0200
>
> > On Wed, May 22, 2013 at 02:50:30PM +0900, Simon Horman wrote:
> >> Add a helper that for use in loops which read data protected by RCU and
> >> may have a large number of iterations. Such an example is dumping the list
> >> of connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next().
> >>
> >> This series also updates IPVS to use the helper.
> >>
> >> Simon Horman (2):
> >> sched: add cond_resched_rcu() helper
> >> ipvs: use cond_resched_rcu() helper when walking connections
> >>
> >> include/linux/sched.h | 9 +++++++++
> >> net/netfilter/ipvs/ip_vs_conn.c | 23 ++++++++---------------
> >> 2 files changed, 17 insertions(+), 15 deletions(-)
> >
> > Acked-by: Peter Zijlstra <peterz@infradead.org>
> >
> > How do you want to go about merging this? Do you want to route it
> > through the net tree or through -tip?
>
> I think we can have Pablo merge it into his netfilter tree.
Yeah, that's what we agreed upon earlier during the review of these
patches.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 11+ messages in thread
end of thread, other threads:[~2013-05-28 8:51 UTC | newest]
Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-05-22 5:50 [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Simon Horman
2013-05-22 5:50 ` [PATCH ipvs-next v3 1/2] sched: add cond_resched_rcu() helper Simon Horman
2013-05-23 11:30 ` Pablo Neira Ayuso
2013-05-22 5:50 ` [PATCH ipvs-next v3 2/2] ipvs: use cond_resched_rcu() helper when walking connections Simon Horman
2013-05-23 11:30 ` Pablo Neira Ayuso
2013-05-22 7:54 ` [PATCH ipvs-next v3 0/2] sched: Add cond_resched_rcu_lock() helper Peter Zijlstra
2013-05-22 8:31 ` David Miller
2013-05-22 9:00 ` Peter Zijlstra
2013-05-23 1:11 ` Simon Horman
2013-05-23 11:31 ` Pablo Neira Ayuso
2013-05-28 8:51 ` Ingo Molnar
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).