[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-devel] Re: Extending virtio_console to support multiple ports

From: Amit Shah
Subject: [Qemu-devel] Re: Extending virtio_console to support multiple ports
Date: Mon, 31 Aug 2009 19:21:47 +0530
User-agent: Mutt/1.5.19 (2009-01-05)

On (Mon) Aug 31 2009 [08:17:21], Anthony Liguori wrote:
>>>> - A lock has to be introduced to fetch one unused buffer from the list
>>>>   and pass it on to the host. And this lock has to be a spinlock, just
>>>>   because writes can be called from irq context.
>>> I don't see a problem here.
>> You mean you don't see a problem in using a spinlock vs not using one?
> Right.  This isn't a fast path.
>> Userspace will typically send the entire buffer to be transmitted in one
>> system call. If it's large, the system call will have to be broken into
>> several. This results in multiple guest system calls, each one to be
>> handled with a spinlock held.
>> Compare this with the entire write handled in one system call in the
>> current method.
> Does it matter?  This isn't a fast path.

The question isn't just about how much work happens inside the spinlock.
It's also a question about introducing spinlocks where they shouldn't

I don't see why such changes have to creep into the kernel.

Can you please explain your rationale for being so rigid about merging
the two drivers?


reply via email to

[Prev in Thread] Current Thread [Next in Thread]