Date: Wed, 04 Jun 2014 23:16:59 +0400 From: "Alexander V. Chernikov" <melifaro@FreeBSD.org> To: John Baldwin <jhb@freebsd.org>, freebsd-hackers@freebsd.org Cc: Konstantin Belousov <kostikbel@gmail.com>, hackers@freebsd.org Subject: Re: Permit init(8) use its own cpuset group. Message-ID: <538F70AB.5030701@FreeBSD.org> In-Reply-To: <201406041106.11659.jhb@freebsd.org> References: <538C8F9A.4020301@FreeBSD.org> <20140602164850.GS3991@kib.kiev.ua> <201406041106.11659.jhb@freebsd.org>
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On 04.06.2014 19:06, John Baldwin wrote:
> On Monday, June 02, 2014 12:48:50 pm Konstantin Belousov wrote:
>> On Mon, Jun 02, 2014 at 06:52:10PM +0400, Alexander V. Chernikov wrote:
>>> Hello list!
>>>
>>> Currently init(8) uses group 1 which is root group.
>>> Modifications of this group affects both kernel and userland threads.
>>> Additionally, such modifications are impossible, for example, in presence
>>> of multi-queue NIC drivers (like igb or ixgbe) which binds their threads
> to
>>> particular cpus.
>>>
>>> Proposed change ("init_cpuset" loader tunable) permits changing cpu
>>> masks for
>>> userland more easily. Restricting user processes to migrate to/from CPU
>>> cores
>>> used for network traffic processing is one of the cases.
>>>
>>> Phabricator: https://phabric.freebsd.org/D141 (the same version attached
>>> inline)
>>>
>>> If there are no objections, I'll commit this next week.
>> Why is the tunable needed ?
> Because some people already depend on doing 'cpuset -l 0 -s 1'. It is also
> documented in our manpages that processes start in cpuset 1 by default so
> that you can use 'cpuset -l 0 -s 1' to move all processes, etc.
>
> For the stated problem (bound ithreads in drivers), I would actually like to
> fix ithreads that are bound to a specific CPU to create a different cpuset
> instead so they don't conflict with set 1.
Yes, this seem to be much better approach.
Please take a look on the new patch (here or in the phabricator).
Comments:
Use different approach for modifyable root set:
* Make sets in 0..15 internal
* Define CPUSET_SET1 & CPUSET_ITHREAD in that range
* Add cpuset_lookup_builtin() to retrieve such cpu sets by id
* Create additional root set for ithreads
* Use this set in ithread_create()
* Change intr_setaffinity() to use cpuset_iroot (do we really need this)?
We can probably do the same for kprocs, but I'm unsure if we really need it.
>
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Index: sys/kern/kern_cpuset.c
===================================================================
--- sys/kern/kern_cpuset.c
+++ sys/kern/kern_cpuset.c
@@ -112,7 +112,7 @@
SYSCTL_INT(_kern_sched, OID_AUTO, cpusetsize, CTLFLAG_RD,
0, sizeof(cpuset_t), "sizeof(cpuset_t)");
-cpuset_t *cpuset_root;
+cpuset_t *cpuset_root, *cpuset_iroot;
/*
* Acquire a reference to a cpuset, all pointers must be tracked with refs.
@@ -213,7 +213,7 @@
* Find a set based on an id. Returns it with a ref.
*/
static struct cpuset *
-cpuset_lookup(cpusetid_t setid, struct thread *td)
+cpuset_lookup_id(cpusetid_t setid)
{
struct cpuset *set;
@@ -227,6 +227,17 @@
cpuset_ref(set);
mtx_unlock_spin(&cpuset_lock);
+ return (set);
+}
+
+static struct cpuset *
+cpuset_lookup(cpusetid_t setid, struct thread *td)
+{
+ struct cpuset *set;
+
+ set = cpuset_lookup_id(setid);
+
+
KASSERT(td != NULL, ("[%s:%d] td is NULL", __func__, __LINE__));
if (set != NULL && jailed(td->td_ucred)) {
struct cpuset *jset, *tset;
@@ -245,6 +256,25 @@
}
/*
+ * Find a set based on an id. Returns it with a ref.
+ */
+struct cpuset *
+cpuset_lookup_builtin(cpusetid_t setid)
+{
+ struct cpuset *set;
+
+ KASSERT(setid <= CPUSET_RESERVED_MAX,
+ ("[%s:%d] wrong set id: %d", __func__, __LINE__, setid));
+
+ set = cpuset_lookup_id(setid);
+
+ KASSERT(set != NULL,
+ ("[%s:%d] set id %d not found", __func__, __LINE__, setid));
+
+ return (set);
+}
+
+/*
* Create a set in the space provided in 'set' with the provided parameters.
* The set is returned with a single ref. May return EDEADLK if the set
* will have no valid cpu based on restrictions from the parent.
@@ -725,9 +755,10 @@
* 1 - The default set which all processes are a member of until changed.
* This allows an administrator to move all threads off of given cpus to
* dedicate them to high priority tasks or save power etc.
+ * 2 - The root set which should be used for all interruot/ithreads.
*/
-struct cpuset *
-cpuset_thread0(void)
+static void
+cpuset_init_sets(void)
{
struct cpuset *set;
int error;
@@ -751,14 +782,31 @@
* Now derive a default, modifiable set from that to give out.
*/
set = uma_zalloc(cpuset_zone, M_WAITOK);
- error = _cpuset_create(set, cpuset_zero, &cpuset_zero->cs_mask, 1);
+ error = _cpuset_create(set, cpuset_zero, &cpuset_zero->cs_mask,
+ CPUSET_SET1);
KASSERT(error == 0, ("Error creating default set: %d\n", error));
/*
- * Initialize the unit allocator. 0 and 1 are allocated above.
+ * Create another root set for interrupt bindings.
*/
- cpuset_unr = new_unrhdr(2, INT_MAX, NULL);
+ set = uma_zalloc(cpuset_zone, M_WAITOK);
+ error = _cpuset_create(set, cpuset_zero, &cpuset_zero->cs_mask,
+ CPUSET_ITHREAD);
+ KASSERT(error == 0, ("Error creating ithread cpuset: %d\n", error));
+ set->cs_flags |= CPU_SET_ROOT;
+ cpuset_iroot = &set->cs_mask;
+ /*
+ * Initialize the unit allocator. Reserve 0..15 for special sets.
+ */
+ cpuset_unr = new_unrhdr(CPUSET_RESERVED_MAX + 1, INT_MAX, NULL);
+}
- return (set);
+struct cpuset *
+cpuset_thread0(void)
+{
+
+ cpuset_init_sets();
+
+ return (cpuset_lookup_builtin(CPUSET_SET1));
}
/*
Index: sys/kern/kern_intr.c
===================================================================
--- sys/kern/kern_intr.c
+++ sys/kern/kern_intr.c
@@ -318,7 +318,7 @@
if (ie->ie_thread != NULL) {
CPU_ZERO(&mask);
if (cpu == NOCPU)
- CPU_COPY(cpuset_root, &mask);
+ CPU_COPY(cpuset_iroot, &mask);
else
CPU_SET(cpu, &mask);
id = ie->ie_thread->it_thread->td_tid;
@@ -334,7 +334,7 @@
if (ie->ie_thread != NULL) {
CPU_ZERO(&mask);
if (ie->ie_cpu == NOCPU)
- CPU_COPY(cpuset_root, &mask);
+ CPU_COPY(cpuset_iroot, &mask);
else
CPU_SET(ie->ie_cpu, &mask);
id = ie->ie_thread->it_thread->td_tid;
@@ -381,7 +381,7 @@
* If we're setting all cpus we can unbind. Otherwise make sure
* only one cpu is in the set.
*/
- if (CPU_CMP(cpuset_root, mask)) {
+ if (CPU_CMP(cpuset_iroot, mask)) {
for (n = 0; n < CPU_SETSIZE; n++) {
if (!CPU_ISSET(n, mask))
continue;
@@ -409,7 +409,7 @@
CPU_ZERO(mask);
mtx_lock(&ie->ie_lock);
if (ie->ie_cpu == NOCPU)
- CPU_COPY(cpuset_root, mask);
+ CPU_COPY(cpuset_iroot, mask);
else
CPU_SET(ie->ie_cpu, mask);
mtx_unlock(&ie->ie_lock);
@@ -461,6 +461,7 @@
TD_SET_IWAIT(td);
thread_unlock(td);
td->td_pflags |= TDP_ITHREAD;
+ td->td_cpuset = cpuset_lookup_builtin(CPUSET_ITHREAD);
ithd->it_thread = td;
CTR2(KTR_INTR, "%s: created %s", __func__, name);
return (ithd);
@@ -485,6 +486,7 @@
TD_SET_IWAIT(td);
thread_unlock(td);
td->td_pflags |= TDP_ITHREAD;
+ td->td_cpuset = cpuset_lookup_builtin(CPUSET_ITHREAD);
ithd->it_thread = td;
CTR2(KTR_INTR, "%s: created %s", __func__, name);
return (ithd);
Index: sys/sys/cpuset.h
===================================================================
--- sys/sys/cpuset.h
+++ sys/sys/cpuset.h
@@ -81,6 +81,10 @@
*/
#define CPUSET_INVALID -1
#define CPUSET_DEFAULT 0
+#define CPUSET_SET1 1
+#define CPUSET_ITHREAD 2
+
+#define CPUSET_RESERVED_MAX 15
#ifdef _KERNEL
LIST_HEAD(setlist, cpuset);
@@ -110,11 +114,12 @@
#define CPU_SET_ROOT 0x0001 /* Set is a root set. */
#define CPU_SET_RDONLY 0x0002 /* No modification allowed. */
-extern cpuset_t *cpuset_root;
+extern cpuset_t *cpuset_root, *cpuset_iroot;
struct prison;
struct proc;
struct cpuset *cpuset_thread0(void);
+struct cpuset *cpuset_lookup_builtin(cpusetid_t setid);
struct cpuset *cpuset_ref(struct cpuset *);
void cpuset_rel(struct cpuset *);
int cpuset_setthread(lwpid_t id, cpuset_t *);
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