From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH][VT] Multithread IDE device model ( was: RE: [Xen-devel] [PATCH]Make IDE dma tranfer run in another thread inqemu) Date: Wed, 26 Oct 2005 17:05:31 -0500 Message-ID: <435FFDAB.4000802@us.ibm.com> References: <37FBBA5F3A361C41AB7CE44558C3448E05884898@pdsmsx403> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <37FBBA5F3A361C41AB7CE44558C3448E05884898@pdsmsx403> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Dong, Eddie" Cc: xen-devel@lists.xensource.com, "Yang, Xiaowei" List-Id: xen-devel@lists.xenproject.org Dong, Eddie wrote: >Hi Anthony: > I think you made misunderstanding to this patch. Current Qemu in >Xen is already DMA enabled. If I remembered correctly, it happens since >we change DM from Bochs to Qemu. > Without this patch, guest IO operation that trigger DMA (like >port 0xc000 write) will wait in Qemu till the DMA operation is >completed, that is original single thread IDE device model mean. > With this patch, a seperate thread will service the dma >operation started by IO operation, and interrupt target processor when >it is completed, while the main thread can rapidly return to guest (like >0xc000 write). > > Yup, the site I linked to has two patches: a DMA patch and a concurrent IO patch. Here's a direct link: http://people.brandeis.edu/~jcoiner/qemu_idedma/qemu_concurrent_io.patch It's using the same basic approach as your patch (another thread waits for completion of IO event). I'm pointing it out though in case there's a desire to stay closer to QEMU upstream when possible. Might enable more code sharing in the future. Regards, Anthony Liguori >Thanks,eddie > >Anthony Liguori wrote: > > >>Hi Eddie, >> >>There was a patch floating around on qemu-devel recently to make IDE >>DMA concurrent. Fabrice is planning to include it in QEMU as long as >>there are no regressions. It may already be in CVS. >> >>See >>http://people.brandeis.edu/~jcoiner/qemu_idedma/qemu_dma_patch.html >> >>The reported performance improvement IO is up to 20% so it's >>definitely worth applying... >> >>Regards, >> >>Anthony Liguori >> >> >> > > >