From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Alexander Duyck <alexanderduyck@fb.com>,
Alex Williamson <alex.williamson@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ben Segall <bsegall@google.com>,
Cornelia Huck <cohuck@redhat.com>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Ingo Molnar <mingo@redhat.com>, Jason Gunthorpe <jgg@nvidia.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Josh Triplett <josh@joshtriplett.org>,
Michal Hocko <mhocko@suse.com>, Nico Pache <npache@redhat.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Peter Zijlstra <peterz@infradead.org>,
Steffen Klassert <steffen.klassert@secunet.com>,
Steve Sistare <steven.sistare@oracle.com>,
Tejun Heo <tj@kernel.org>, Tim Chen <tim.c.chen@linux.intel.com>,
Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-mm@kvack.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
Daniel Jordan <daniel.m.jordan@oracle.com>
Subject: [RFC 11/16] padata: Cap helpers started to online CPUs
Date: Wed, 5 Jan 2022 19:46:51 -0500 [thread overview]
Message-ID: <20220106004656.126790-12-daniel.m.jordan@oracle.com> (raw)
In-Reply-To: <20220106004656.126790-1-daniel.m.jordan@oracle.com>
padata can start num_possible_cpus() helpers, but this is too many
considering that every job's main thread participates and there may
be fewer online than possible CPUs.
Limit overall concurrency, including main thread(s), to
num_online_cpus() with the padata_works_inuse counter to prevent
CPU-intensive threads flooding the system in case of concurrent jobs.
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
---
kernel/padata.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/kernel/padata.c b/kernel/padata.c
index 0f4002ed1518..e27988d3e9ed 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -50,6 +50,7 @@ struct padata_work {
static DEFINE_SPINLOCK(padata_works_lock);
static struct padata_work *padata_works;
+static unsigned int padata_works_inuse;
static LIST_HEAD(padata_free_works);
struct padata_mt_job_state {
@@ -98,11 +99,16 @@ static struct padata_work *padata_work_alloc(void)
lockdep_assert_held(&padata_works_lock);
- if (list_empty(&padata_free_works))
- return NULL; /* No more work items allowed to be queued. */
+ /* Are more work items allowed to be queued? */
+ if (padata_works_inuse >= num_online_cpus())
+ return NULL;
+
+ if (WARN_ON_ONCE(list_empty(&padata_free_works)))
+ return NULL;
pw = list_first_entry(&padata_free_works, struct padata_work, pw_list);
list_del(&pw->pw_list);
+ ++padata_works_inuse;
return pw;
}
@@ -111,7 +117,11 @@ static int padata_work_alloc_mt(int nworks, struct list_head *head)
int i;
spin_lock(&padata_works_lock);
- /* Start at 1 because the current task participates in the job. */
+ /*
+ * Increment inuse and start iterating at 1 to account for the main
+ * thread participating in the job with its stack-allocated work.
+ */
+ ++padata_works_inuse;
for (i = 1; i < nworks; ++i) {
struct padata_work *pw = padata_work_alloc();
@@ -128,20 +138,22 @@ static void padata_work_free(struct padata_work *pw)
{
lockdep_assert_held(&padata_works_lock);
list_add(&pw->pw_list, &padata_free_works);
+ WARN_ON_ONCE(!padata_works_inuse);
+ --padata_works_inuse;
}
static void padata_works_free(struct list_head *works)
{
struct padata_work *cur, *next;
- if (list_empty(works))
- return;
-
spin_lock(&padata_works_lock);
list_for_each_entry_safe(cur, next, works, pw_list) {
list_del(&cur->pw_list);
padata_work_free(cur);
}
+ /* To account for the main thread finishing its part of the job. */
+ WARN_ON_ONCE(!padata_works_inuse);
+ --padata_works_inuse;
spin_unlock(&padata_works_lock);
}
--
2.34.1
next prev parent reply other threads:[~2022-01-06 0:51 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-06 0:46 [RFC 00/16] padata, vfio, sched: Multithreaded VFIO page pinning Daniel Jordan
2022-01-06 0:46 ` [RFC 01/16] padata: Remove __init from multithreading functions Daniel Jordan
2022-01-06 0:46 ` [RFC 02/16] padata: Return first error from a job Daniel Jordan
2022-01-06 0:46 ` [RFC 03/16] padata: Add undo support Daniel Jordan
2022-01-06 0:46 ` [RFC 04/16] padata: Detect deadlocks between main and helper threads Daniel Jordan
2022-01-06 0:46 ` [RFC 05/16] vfio/type1: Pass mm to vfio_pin_pages_remote() Daniel Jordan
2022-01-06 0:46 ` [RFC 06/16] vfio/type1: Refactor dma map removal Daniel Jordan
2022-01-06 0:46 ` [RFC 07/16] vfio/type1: Parallelize vfio_pin_map_dma() Daniel Jordan
2022-01-06 0:46 ` [RFC 08/16] vfio/type1: Cache locked_vm to ease mmap_lock contention Daniel Jordan
2022-01-06 0:53 ` Jason Gunthorpe
2022-01-06 1:17 ` Daniel Jordan
2022-01-06 12:34 ` Jason Gunthorpe
2022-01-06 21:05 ` Alex Williamson
2022-01-07 0:19 ` Jason Gunthorpe
2022-01-07 3:06 ` Daniel Jordan
2022-01-07 15:18 ` Jason Gunthorpe
2022-01-07 16:39 ` Daniel Jordan
2022-01-06 0:46 ` [RFC 09/16] padata: Use kthreads in do_multithreaded Daniel Jordan
2022-01-06 0:46 ` [RFC 10/16] padata: Helpers should respect main thread's CPU affinity Daniel Jordan
2022-01-06 0:46 ` Daniel Jordan [this message]
2022-01-06 0:46 ` [RFC 12/16] sched, padata: Bound max threads with max_cfs_bandwidth_cpus() Daniel Jordan
2022-01-06 0:46 ` [RFC 13/16] padata: Run helper threads at MAX_NICE Daniel Jordan
2022-01-06 0:46 ` [RFC 14/16] padata: Nice helper threads one by one to prevent starvation Daniel Jordan
2022-01-06 0:46 ` [RFC 15/16] sched/fair: Account kthread runtime debt for CFS bandwidth Daniel Jordan
2022-01-11 11:58 ` Peter Zijlstra
2022-01-11 16:29 ` Daniel Jordan
2022-01-12 20:18 ` Tejun Heo
2022-01-13 21:08 ` Daniel Jordan
2022-01-13 21:11 ` Daniel Jordan
2022-01-14 9:31 ` Peter Zijlstra
2022-01-14 9:40 ` Peter Zijlstra
2022-01-14 16:38 ` Tejun Heo
2022-01-18 17:40 ` Daniel Jordan
2022-01-14 16:30 ` Tejun Heo
2022-01-18 17:32 ` Daniel Jordan
2022-01-06 0:46 ` [RFC 16/16] sched/fair: Consider kthread debt in cputime Daniel Jordan
2022-01-06 1:13 ` [RFC 00/16] padata, vfio, sched: Multithreaded VFIO page pinning Jason Gunthorpe
2022-01-07 3:03 ` Daniel Jordan
2022-01-07 17:12 ` Jason Gunthorpe
2022-01-10 22:27 ` Daniel Jordan
2022-01-11 0:17 ` Jason Gunthorpe
2022-01-11 16:20 ` Daniel Jordan
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