From: Paolo Bonzini <pbonzini@redhat.com>
To: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [RFC PATCH] VFIO: Add a parameter to force nonthread IRQ
Date: Wed, 28 Oct 2015 19:28:57 +0100 [thread overview]
Message-ID: <563113E9.2040608@redhat.com> (raw)
In-Reply-To: <20151028175013.GA21961@jnakajim-build>
On 28/10/2015 18:50, Yunhong Jiang wrote:
> > No, I don't think you can use raw_spinlock there. The problem is not
> > just eventfd_signal, it is especially wake_up_locked_poll. You cannot
> > convert the whole workqueue infrastructure to use raw_spinlock.
>
> You mean the waitqueue, instead of workqueue, right?
Yes.
> One choice is to change
> the eventfd to use simple wait queue, which is raw_spinlock. But use simple
> waitqueue on eventfd may in fact impact real time latency if not in this
> scenario.
Userspace can put an arbitrary amount of tasks on the work queue, so
it's not possible to use a simple wait queue. It would also touch
multiple subsystems, so it's much better to bypass the eventfd completely.
Paolo
prev parent reply other threads:[~2015-10-28 18:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-27 1:20 [RFC PATCH] VFIO: Add a parameter to force nonthread IRQ Yunhong Jiang
2015-10-27 3:37 ` Alex Williamson
2015-10-27 6:35 ` Yunhong Jiang
2015-10-27 9:29 ` Paolo Bonzini
2015-10-27 21:26 ` Yunhong Jiang
2015-10-28 0:44 ` Paolo Bonzini
2015-10-28 16:00 ` Alex Williamson
2015-10-28 17:05 ` Paolo Bonzini
2015-10-28 23:54 ` Marcelo Tosatti
2015-10-29 3:11 ` Alex Williamson
2015-10-29 9:45 ` Paolo Bonzini
2015-10-30 6:16 ` Yunhong Jiang
2015-11-02 9:17 ` Paolo Bonzini
2015-10-28 17:50 ` Yunhong Jiang
2015-10-28 18:18 ` Alex Williamson
2015-10-28 21:46 ` Yunhong Jiang
2015-10-28 18:28 ` Paolo Bonzini [this message]
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