From: Mike Galbraith <efault@gmx.de>
To: Linus Torvalds <torvalds@linux-foundation.org>,
Paolo Abeni <pabeni@redhat.com>
Cc: David Miller <davem@davemloft.net>,
Frederic Weisbecker <frederic@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Sasha Levin <alexander.levin@verizon.com>,
Peter Zijlstra <peterz@infradead.org>,
Mauro Carvalho Chehab <mchehab@s-opensource.com>,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Wanpeng Li <wanpeng.li@hotmail.com>,
Dmitry Safonov <dima@arista.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Radu Rendec <rrendec@arista.com>, Ingo Molnar <mingo@kernel.org>,
Stanislaw Gruszka <sgruszka@redhat.com>,
Rik van Riel <riel@redhat.com>,
Eric Dumazet <edumazet@google.com>
Subject: Re: [RFC PATCH 0/4] softirq: Per vector threading v3
Date: Tue, 23 Jan 2018 19:01:20 +0100 [thread overview]
Message-ID: <1516730480.6999.2.camel@gmx.de> (raw)
In-Reply-To: <CA+55aFwEMe=jV7pvV2dWFKrQ--mAw3buXhdJ-Qk2u-290rTQQQ@mail.gmail.com>
On Tue, 2018-01-23 at 09:42 -0800, Linus Torvalds wrote:
> On Tue, Jan 23, 2018 at 8:57 AM, Paolo Abeni <pabeni@redhat.com> wrote:
> >
> >> Or is it that the workqueue execution is simply not yielding for some
> >> reason?
> >
> > It's like that.
> >
> > I spent little time on it, so I haven't many data point. I'll try to
> > investigate the scenario later this week.
>
> Hmm. workqueues seem to use cond_resched_rcu_qs(), which does a
> cond_resched() (and a RCU quiescent note).
>
> But I wonder if the test triggers the "lets run lots of workqueue
> threads", and then the single-threaded user space just gets blown out
> of the water by many kernel threads. Each thread gets its own "fair"
> amount of CPU, but..
If folks aren't careful with workqueues, they can be a generic
starvation problem. Like the below in the here and now.
fs/nfs: Add a resched point to nfs_commit_release_pages()
During heavy NFS write, kworkers can do very large amounts of work
without scheduling (82ms traced). Add a resched point.
Signed-off-by: Mike Galbraith <efault@gmx.de>
Suggested-by: Trond Myklebust <trondmy@primarydata.com>
---
fs/nfs/write.c | 1 +
1 file changed, 1 insertion(+)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1837,6 +1837,7 @@ static void nfs_commit_release_pages(str
set_bit(NFS_CONTEXT_RESEND_WRITES, &req->wb_context->flags);
next:
nfs_unlock_and_release_request(req);
+ cond_resched();
}
nfss = NFS_SERVER(data->inode);
if (atomic_long_read(&nfss->writeback) < NFS_CONGESTION_OFF_THRESH)
next prev parent reply other threads:[~2018-01-23 18:02 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-19 15:46 [RFC PATCH 0/4] softirq: Per vector threading v3 Frederic Weisbecker
2018-01-19 15:46 ` [RFC PATCH 1/4] softirq: Limit vector to a single iteration on IRQ tail Frederic Weisbecker
2018-01-19 16:16 ` David Miller
2018-01-19 18:25 ` Linus Torvalds
2018-01-19 18:47 ` David Miller
2018-01-21 16:30 ` Frederic Weisbecker
2018-01-21 16:57 ` David Miller
2018-01-19 15:46 ` [RFC PATCH 2/4] softirq: Per vector deferment to workqueue Frederic Weisbecker
2018-01-20 8:41 ` Pavan Kondeti
2018-01-21 16:11 ` Frederic Weisbecker
2018-01-21 17:50 ` Pavan Kondeti
2018-01-21 20:48 ` Frederic Weisbecker
2018-02-08 17:44 ` Sebastian Andrzej Siewior
2018-02-08 18:45 ` David Miller
2018-02-08 20:14 ` Dmitry Safonov
2018-02-08 20:22 ` David Miller
2018-02-08 20:30 ` Dmitry Safonov
2018-02-09 4:11 ` Mike Galbraith
2018-02-09 12:35 ` Sebastian Andrzej Siewior
2018-02-15 16:13 ` Frederic Weisbecker
2018-02-15 16:58 ` Sebastian Andrzej Siewior
2018-01-19 15:46 ` [RFC PATCH 3/4] softirq: Defer to workqueue when rescheduling is needed Frederic Weisbecker
2018-01-19 15:46 ` [RFC PATCH 4/4] softirq: Replace ksoftirqd with workqueues entirely Frederic Weisbecker
2018-01-22 19:58 ` [RFC PATCH 0/4] softirq: Per vector threading v3 Mauro Carvalho Chehab
2018-01-23 10:13 ` Paolo Abeni
2018-01-23 12:32 ` Dmitry Safonov
2018-01-24 2:12 ` Frederic Weisbecker
2018-01-23 16:22 ` David Miller
2018-01-23 16:57 ` Paolo Abeni
2018-01-23 17:42 ` Linus Torvalds
2018-01-23 18:01 ` Mike Galbraith [this message]
2018-01-23 18:24 ` David Miller
2018-01-24 1:57 ` Frederic Weisbecker
2018-01-24 2:01 ` Frederic Weisbecker
2018-01-24 14:54 ` Paolo Abeni
2018-01-24 15:05 ` David Miller
2018-01-24 16:11 ` Paolo Abeni
2018-02-07 14:18 ` Mauro Carvalho Chehab
2018-03-01 15:21 ` Frederic Weisbecker
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