* [PATCH] sched/x86: construct all sibling maps if smt
@ 2013-05-27 17:09 Andrew Jones
2013-05-29 10:26 ` Andrew Jones
2013-05-29 12:48 ` [PATCH v2] " Andrew Jones
0 siblings, 2 replies; 6+ messages in thread
From: Andrew Jones @ 2013-05-27 17:09 UTC (permalink / raw)
To: tglx, mingo, hpa, x86, a.p.zijlstra, fenghua.yu; +Cc: linux-kernel
Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()") broke
the construction of sibling maps, which also broke the booted_cores
accounting.
Before the rewrite, if smt was present, then each map was updated for
each smt sibling. After the rewrite only cpu_sibling_mask gets updated,
as the llc and core maps depend on 'has_mc = x86_max_cores > 1' instead.
This leads to problems with topologies like the following
(qemu -smp sockets=2,cores=1,threads=2)
processor : 0
physical id : 0
siblings : 1 <= should be 2
core id : 0
cpu cores : 1
processor : 1
physical id : 0
siblings : 1 <= should be 2
core id : 0
cpu cores : 0 <= should be 1
processor : 2
physical id : 1
siblings : 1 <= should be 2
core id : 0
cpu cores : 1
processor : 3
physical id : 1
siblings : 1 <= should be 2
core id : 0
cpu cores : 0 <= should be 1
This patch restores the former construction by defining has_mc as
(has_smt || x86_max_cores > 1). This should be fine as there were no
(has_smt && !has_mc) conditions in the context.
Signed-off-by: Andrew Jones <drjones@redhat.com>
---
arch/x86/kernel/smpboot.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9c73b51817e47..886a3234eaff3 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
void __cpuinit set_cpu_sibling_map(int cpu)
{
- bool has_mc = boot_cpu_data.x86_max_cores > 1;
bool has_smt = smp_num_siblings > 1;
+ bool has_mc = has_smt || boot_cpu_data.x86_max_cores > 1;
struct cpuinfo_x86 *c = &cpu_data(cpu);
struct cpuinfo_x86 *o;
int i;
cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
- if (!has_smt && !has_mc) {
+ if (!has_mc) {
cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
cpumask_set_cpu(cpu, cpu_core_mask(cpu));
--
1.8.1.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/x86: construct all sibling maps if smt
2013-05-27 17:09 [PATCH] sched/x86: construct all sibling maps if smt Andrew Jones
@ 2013-05-29 10:26 ` Andrew Jones
2013-05-29 11:06 ` Peter Zijlstra
2013-05-29 12:48 ` [PATCH v2] " Andrew Jones
1 sibling, 1 reply; 6+ messages in thread
From: Andrew Jones @ 2013-05-29 10:26 UTC (permalink / raw)
To: tglx, mingo, hpa, x86, a.p.zijlstra, fenghua.yu; +Cc: linux-kernel
On Mon, May 27, 2013 at 07:09:00PM +0200, Andrew Jones wrote:
> Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()") broke
> the construction of sibling maps, which also broke the booted_cores
> accounting.
>
> Before the rewrite, if smt was present, then each map was updated for
> each smt sibling. After the rewrite only cpu_sibling_mask gets updated,
> as the llc and core maps depend on 'has_mc = x86_max_cores > 1' instead.
> This leads to problems with topologies like the following
>
> (qemu -smp sockets=2,cores=1,threads=2)
>
> processor : 0
> physical id : 0
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 1
>
> processor : 1
> physical id : 0
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 0 <= should be 1
>
> processor : 2
> physical id : 1
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 1
>
> processor : 3
> physical id : 1
> siblings : 1 <= should be 2
> core id : 0
> cpu cores : 0 <= should be 1
>
> This patch restores the former construction by defining has_mc as
> (has_smt || x86_max_cores > 1). This should be fine as there were no
> (has_smt && !has_mc) conditions in the context.
>
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
> arch/x86/kernel/smpboot.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 9c73b51817e47..886a3234eaff3 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
>
> void __cpuinit set_cpu_sibling_map(int cpu)
> {
> - bool has_mc = boot_cpu_data.x86_max_cores > 1;
> bool has_smt = smp_num_siblings > 1;
> + bool has_mc = has_smt || boot_cpu_data.x86_max_cores > 1;
> struct cpuinfo_x86 *c = &cpu_data(cpu);
> struct cpuinfo_x86 *o;
> int i;
>
> cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
>
> - if (!has_smt && !has_mc) {
> + if (!has_mc) {
> cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
> cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
> cpumask_set_cpu(cpu, cpu_core_mask(cpu));
> --
> 1.8.1.4
>
Any acks? This patch fixes a regression. Also, in case anybody is
wondering, this is not the same regression as was already fixed with
ceb1cbac8eda6 sched/x86: Calculate booted cores after construction of sibling_mask
(Hmm, I probably should have renamed has_mc to has_mp, as the redefinition
expands its scope. I'm not sure if that deserves a v2 though.)
drew
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/x86: construct all sibling maps if smt
2013-05-29 10:26 ` Andrew Jones
@ 2013-05-29 11:06 ` Peter Zijlstra
2013-05-29 11:11 ` Ingo Molnar
0 siblings, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2013-05-29 11:06 UTC (permalink / raw)
To: Andrew Jones; +Cc: tglx, mingo, hpa, x86, fenghua.yu, linux-kernel
On Wed, May 29, 2013 at 12:26:01PM +0200, Andrew Jones wrote:
> On Mon, May 27, 2013 at 07:09:00PM +0200, Andrew Jones wrote:
> > Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()") broke
> > the construction of sibling maps, which also broke the booted_cores
> > accounting.
> >
> > Before the rewrite, if smt was present, then each map was updated for
> > each smt sibling. After the rewrite only cpu_sibling_mask gets updated,
> > as the llc and core maps depend on 'has_mc = x86_max_cores > 1' instead.
> > This leads to problems with topologies like the following
> >
> > (qemu -smp sockets=2,cores=1,threads=2)
> >
> > processor : 0
> > physical id : 0
> > siblings : 1 <= should be 2
> > core id : 0
> > cpu cores : 1
> >
> > processor : 1
> > physical id : 0
> > siblings : 1 <= should be 2
> > core id : 0
> > cpu cores : 0 <= should be 1
> >
> > processor : 2
> > physical id : 1
> > siblings : 1 <= should be 2
> > core id : 0
> > cpu cores : 1
> >
> > processor : 3
> > physical id : 1
> > siblings : 1 <= should be 2
> > core id : 0
> > cpu cores : 0 <= should be 1
> >
> > This patch restores the former construction by defining has_mc as
> > (has_smt || x86_max_cores > 1). This should be fine as there were no
> > (has_smt && !has_mc) conditions in the context.
> >
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > ---
> > arch/x86/kernel/smpboot.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> > index 9c73b51817e47..886a3234eaff3 100644
> > --- a/arch/x86/kernel/smpboot.c
> > +++ b/arch/x86/kernel/smpboot.c
> > @@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
> >
> > void __cpuinit set_cpu_sibling_map(int cpu)
> > {
> > - bool has_mc = boot_cpu_data.x86_max_cores > 1;
> > bool has_smt = smp_num_siblings > 1;
> > + bool has_mc = has_smt || boot_cpu_data.x86_max_cores > 1;
> > struct cpuinfo_x86 *c = &cpu_data(cpu);
> > struct cpuinfo_x86 *o;
> > int i;
> >
> > cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
> >
> > - if (!has_smt && !has_mc) {
> > + if (!has_mc) {
> > cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
> > cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
> > cpumask_set_cpu(cpu, cpu_core_mask(cpu));
> > --
> > 1.8.1.4
> >
>
> Any acks? This patch fixes a regression. Also, in case anybody is
> wondering, this is not the same regression as was already fixed with
>
> ceb1cbac8eda6 sched/x86: Calculate booted cores after construction of sibling_mask
>
> (Hmm, I probably should have renamed has_mc to has_mp, as the redefinition
> expands its scope. I'm not sure if that deserves a v2 though.)
Right, took me a while to bend my brain around that code again -- I
obviously don't have the best track record since this is the second bug
in it since I rewrote the thing (with the intent of making it 'easier'
to read ha!).
Yes, I think your patch is correct, and your suggestion of doing
s/has_mc/has_mp/ seems a sensible one too.
Thanks!
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] sched/x86: construct all sibling maps if smt
2013-05-29 11:06 ` Peter Zijlstra
@ 2013-05-29 11:11 ` Ingo Molnar
0 siblings, 0 replies; 6+ messages in thread
From: Ingo Molnar @ 2013-05-29 11:11 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Andrew Jones, tglx, mingo, hpa, x86, fenghua.yu, linux-kernel
* Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, May 29, 2013 at 12:26:01PM +0200, Andrew Jones wrote:
> > On Mon, May 27, 2013 at 07:09:00PM +0200, Andrew Jones wrote:
> > > Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()") broke
> > > the construction of sibling maps, which also broke the booted_cores
> > > accounting.
> > >
> > > Before the rewrite, if smt was present, then each map was updated for
> > > each smt sibling. After the rewrite only cpu_sibling_mask gets updated,
> > > as the llc and core maps depend on 'has_mc = x86_max_cores > 1' instead.
> > > This leads to problems with topologies like the following
> > >
> > > (qemu -smp sockets=2,cores=1,threads=2)
> > >
> > > processor : 0
> > > physical id : 0
> > > siblings : 1 <= should be 2
> > > core id : 0
> > > cpu cores : 1
> > >
> > > processor : 1
> > > physical id : 0
> > > siblings : 1 <= should be 2
> > > core id : 0
> > > cpu cores : 0 <= should be 1
> > >
> > > processor : 2
> > > physical id : 1
> > > siblings : 1 <= should be 2
> > > core id : 0
> > > cpu cores : 1
> > >
> > > processor : 3
> > > physical id : 1
> > > siblings : 1 <= should be 2
> > > core id : 0
> > > cpu cores : 0 <= should be 1
> > >
> > > This patch restores the former construction by defining has_mc as
> > > (has_smt || x86_max_cores > 1). This should be fine as there were no
> > > (has_smt && !has_mc) conditions in the context.
> > >
> > > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > > ---
> > > arch/x86/kernel/smpboot.c | 4 ++--
> > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> > > index 9c73b51817e47..886a3234eaff3 100644
> > > --- a/arch/x86/kernel/smpboot.c
> > > +++ b/arch/x86/kernel/smpboot.c
> > > @@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
> > >
> > > void __cpuinit set_cpu_sibling_map(int cpu)
> > > {
> > > - bool has_mc = boot_cpu_data.x86_max_cores > 1;
> > > bool has_smt = smp_num_siblings > 1;
> > > + bool has_mc = has_smt || boot_cpu_data.x86_max_cores > 1;
> > > struct cpuinfo_x86 *c = &cpu_data(cpu);
> > > struct cpuinfo_x86 *o;
> > > int i;
> > >
> > > cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
> > >
> > > - if (!has_smt && !has_mc) {
> > > + if (!has_mc) {
> > > cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
> > > cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
> > > cpumask_set_cpu(cpu, cpu_core_mask(cpu));
> > > --
> > > 1.8.1.4
> > >
> >
> > Any acks? This patch fixes a regression. Also, in case anybody is
> > wondering, this is not the same regression as was already fixed with
> >
> > ceb1cbac8eda6 sched/x86: Calculate booted cores after construction of sibling_mask
> >
> > (Hmm, I probably should have renamed has_mc to has_mp, as the redefinition
> > expands its scope. I'm not sure if that deserves a v2 though.)
>
> Right, took me a while to bend my brain around that code again -- I
> obviously don't have the best track record since this is the second bug
> in it since I rewrote the thing (with the intent of making it 'easier'
> to read ha!).
>
> Yes, I think your patch is correct, and your suggestion of doing
> s/has_mc/has_mp/ seems a sensible one too.
>
> Thanks!
Andrew, it would be nice to have a -v2 with that rename and with Peter's
Acked-by included.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH v2] sched/x86: construct all sibling maps if smt
2013-05-27 17:09 [PATCH] sched/x86: construct all sibling maps if smt Andrew Jones
2013-05-29 10:26 ` Andrew Jones
@ 2013-05-29 12:48 ` Andrew Jones
2013-05-31 12:50 ` [tip:sched/urgent] sched/x86: Construct " tip-bot for Andrew Jones
1 sibling, 1 reply; 6+ messages in thread
From: Andrew Jones @ 2013-05-29 12:48 UTC (permalink / raw)
To: tglx, mingo, hpa, x86, a.p.zijlstra, fenghua.yu; +Cc: linux-kernel
Commit 316ad248307fb ("sched/x86: Rewrite set_cpu_sibling_map()") broke
the construction of sibling maps, which also broke the booted_cores
accounting.
Before the rewrite, if smt was present, then each map was updated for
each smt sibling. After the rewrite only cpu_sibling_mask gets updated,
as the llc and core maps depend on 'has_mc = x86_max_cores > 1' instead.
This leads to problems with topologies like the following
(qemu -smp sockets=2,cores=1,threads=2)
processor : 0
physical id : 0
siblings : 1 <= should be 2
core id : 0
cpu cores : 1
processor : 1
physical id : 0
siblings : 1 <= should be 2
core id : 0
cpu cores : 0 <= should be 1
processor : 2
physical id : 1
siblings : 1 <= should be 2
core id : 0
cpu cores : 1
processor : 3
physical id : 1
siblings : 1 <= should be 2
core id : 0
cpu cores : 0 <= should be 1
This patch restores the former construction by defining has_mc as
(has_smt || x86_max_cores > 1). This should be fine as there were no
(has_smt && !has_mc) conditions in the context.
v2:
- rename has_mc to has_mp now that it's not just for cores
Signed-off-by: Andrew Jones <drjones@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/kernel/smpboot.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9c73b51817e47..bfd348e993692 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
void __cpuinit set_cpu_sibling_map(int cpu)
{
- bool has_mc = boot_cpu_data.x86_max_cores > 1;
bool has_smt = smp_num_siblings > 1;
+ bool has_mp = has_smt || boot_cpu_data.x86_max_cores > 1;
struct cpuinfo_x86 *c = &cpu_data(cpu);
struct cpuinfo_x86 *o;
int i;
cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
- if (!has_smt && !has_mc) {
+ if (!has_mp) {
cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
cpumask_set_cpu(cpu, cpu_core_mask(cpu));
@@ -394,7 +394,7 @@ void __cpuinit set_cpu_sibling_map(int cpu)
if ((i == cpu) || (has_smt && match_smt(c, o)))
link_mask(sibling, cpu, i);
- if ((i == cpu) || (has_mc && match_llc(c, o)))
+ if ((i == cpu) || (has_mp && match_llc(c, o)))
link_mask(llc_shared, cpu, i);
}
@@ -406,7 +406,7 @@ void __cpuinit set_cpu_sibling_map(int cpu)
for_each_cpu(i, cpu_sibling_setup_mask) {
o = &cpu_data(i);
- if ((i == cpu) || (has_mc && match_mc(c, o))) {
+ if ((i == cpu) || (has_mp && match_mc(c, o))) {
link_mask(core, cpu, i);
/*
--
1.8.1.4
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [tip:sched/urgent] sched/x86: Construct all sibling maps if smt
2013-05-29 12:48 ` [PATCH v2] " Andrew Jones
@ 2013-05-31 12:50 ` tip-bot for Andrew Jones
0 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Andrew Jones @ 2013-05-31 12:50 UTC (permalink / raw)
To: linux-tip-commits; +Cc: linux-kernel, hpa, mingo, drjones, peterz, tglx
Commit-ID: b0bc225d0e5de887340d4d92a8c594ef0f60d412
Gitweb: http://git.kernel.org/tip/b0bc225d0e5de887340d4d92a8c594ef0f60d412
Author: Andrew Jones <drjones@redhat.com>
AuthorDate: Wed, 29 May 2013 14:48:15 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 31 May 2013 13:10:38 +0200
sched/x86: Construct all sibling maps if smt
Commit 316ad248307fb ("sched/x86: Rewrite
set_cpu_sibling_map()") broke the construction of sibling maps,
which also broke the booted_cores accounting.
Before the rewrite, if smt was present, then each map was
updated for each smt sibling. After the rewrite only
cpu_sibling_mask gets updated, as the llc and core maps depend
on 'has_mc = x86_max_cores > 1' instead. This leads to problems
with topologies like the following
(qemu -smp sockets=2,cores=1,threads=2)
processor : 0
physical id : 0
siblings : 1 <= should be 2
core id : 0
cpu cores : 1
processor : 1
physical id : 0
siblings : 1 <= should be 2
core id : 0
cpu cores : 0 <= should be 1
processor : 2
physical id : 1
siblings : 1 <= should be 2
core id : 0
cpu cores : 1
processor : 3
physical id : 1
siblings : 1 <= should be 2
core id : 0
cpu cores : 0 <= should be 1
This patch restores the former construction by defining has_mc
as (has_smt || x86_max_cores > 1). This should be fine as there
were no (has_smt && !has_mc) conditions in the context.
Aso rename has_mc to has_mp now that it's not just for cores.
Signed-off-by: Andrew Jones <drjones@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: a.p.zijlstra@chello.nl
Cc: fenghua.yu@intel.com
Link: http://lkml.kernel.org/r/1369831695-11970-1-git-send-email-drjones@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/smpboot.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 9c73b51..bfd348e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -372,15 +372,15 @@ static bool __cpuinit match_mc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
void __cpuinit set_cpu_sibling_map(int cpu)
{
- bool has_mc = boot_cpu_data.x86_max_cores > 1;
bool has_smt = smp_num_siblings > 1;
+ bool has_mp = has_smt || boot_cpu_data.x86_max_cores > 1;
struct cpuinfo_x86 *c = &cpu_data(cpu);
struct cpuinfo_x86 *o;
int i;
cpumask_set_cpu(cpu, cpu_sibling_setup_mask);
- if (!has_smt && !has_mc) {
+ if (!has_mp) {
cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
cpumask_set_cpu(cpu, cpu_core_mask(cpu));
@@ -394,7 +394,7 @@ void __cpuinit set_cpu_sibling_map(int cpu)
if ((i == cpu) || (has_smt && match_smt(c, o)))
link_mask(sibling, cpu, i);
- if ((i == cpu) || (has_mc && match_llc(c, o)))
+ if ((i == cpu) || (has_mp && match_llc(c, o)))
link_mask(llc_shared, cpu, i);
}
@@ -406,7 +406,7 @@ void __cpuinit set_cpu_sibling_map(int cpu)
for_each_cpu(i, cpu_sibling_setup_mask) {
o = &cpu_data(i);
- if ((i == cpu) || (has_mc && match_mc(c, o))) {
+ if ((i == cpu) || (has_mp && match_mc(c, o))) {
link_mask(core, cpu, i);
/*
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-05-31 12:50 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-05-27 17:09 [PATCH] sched/x86: construct all sibling maps if smt Andrew Jones
2013-05-29 10:26 ` Andrew Jones
2013-05-29 11:06 ` Peter Zijlstra
2013-05-29 11:11 ` Ingo Molnar
2013-05-29 12:48 ` [PATCH v2] " Andrew Jones
2013-05-31 12:50 ` [tip:sched/urgent] sched/x86: Construct " tip-bot for Andrew Jones
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).