[Top][All Lists]

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

Re: [Qemu-devel] [PATCH] RFC: Add new block driver for the VDI format

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH] RFC: Add new block driver for the VDI format
Date: Sun, 02 Aug 2009 17:27:14 +0300
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1b3pre) Gecko/20090513 Fedora/3.0-2.3.beta2.fc11 Lightning/1.0pre Thunderbird/3.0b2

On 07/06/2009 04:37 PM, Anthony Liguori wrote:

I'd really like to get rid of synchronous IO functions in the block layer. One way to do this is to insist that all new block drivers only implement the AIO functions.

I think we should make this decree but I'd like to know if other people think this is unreasonable first. One potential model of block drivers would involve synchronous IO and threads. I'm not a big fan of that model and I don't think it's an easy conversion from today's synchronous IO drivers to that model because the locking and re-entrance needs careful consideration.

I agree that sync+threads is not easy, but well performing async is much, much harder. Consider that qcow2 still has synchronous operations, and that eliminating the RMW when writing a partial cluster concurrently (a very common operation with 64K clusters) is very hard to do ayncly and much easier syncly.

Given in addition the large numbers of format drivers, I think we should prefer sync+threads over trying to convert all format drivers to full async.

error compiling committee.c: too many arguments to function

reply via email to

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