On Mon, Mar 23, 2009 at 12:14:58PM -0500, Anthony Liguori wrote: > I'd like to see the O_DIRECT bounce buffering removed in favor of the > DMA API bouncing. Once that happens, raw_read and raw_pread can > disappear. block-raw-posix becomes much simpler. See my vectored I/O patches for doing the bounce buffering at the optimal place for the aio path. Note that from my reading of the qcow/qcow2 code they might send down unaligned requests, which is something the dma api would not help with. For the buffered I/O path we will always have to do some sort of buffering due to all the partition header reading / etc. And given how that part isn't performance critical my preference would be to keep doing it in bdrv_pread/write and guarantee the lowlevel drivers proper alignment. > We would drop the signaling stuff and have the thread pool use an fd to > signal. The big problem with that right now is that it'll cause a > performance regression for certain platforms until we have the IO thread > in place. Talking about signaling, does anyone remember why the Linux signalfd/ eventfd support is only in kvm but not in upstream qemu? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
