Messages in this thread | | | Date | Wed, 06 Jun 2012 07:03:06 +0800 | From | Anthony Liguori <> | Subject | Re: [Qemu-devel] [RFC PATCH 1/2] ivring: Add a ring-buffer driver on IVShmem |
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On 06/05/2012 09:10 PM, Borislav Petkov wrote: > On Tue, Jun 05, 2012 at 10:01:17PM +0900, Yoshihiro YUNOMAE wrote: >> This patch adds a ring-buffer driver for IVShmem device, a virtual RAM device in >> QEMU. This driver can be used as a ring-buffer for kernel logging or tracing of >> a guest OS by recording kernel programing or SystemTap. >> >> This ring-buffer driver is implemented very simple. First 4kB of shared memory >> region is control structure of a ring-buffer. In this region, some values for >> managing the ring-buffer is stored such as bits and mask of whole memory size, >> writing position, threshold value for notification to a reader on a host OS. >> This region is used by the reader to know writing position. Then, "total >> memory size - 4kB" equals to usable memory region for recording data. >> This ring-buffer driver records any data from start to end of the writable >> memory region. >> >> When writing size exceeds a threshold value, this driver can notify a reader >> to read data by using writel(). As this later patch, reader does not have any >> function for receiving the notification. This notification feature will be used >> near the future. >> >> As a writer records data in this ring-buffer, spinlock function is used to >> avoid competing by some writers in multi CPU environment. Not to use spinlock, >> lockless ring-buffer like as ftrace and one ring-buffer one CPU will be >> implemented near the future. > > Yet another ring buffer? > > We already have an ftrace and perf ring buffer, can't you use one of those?
Not to mention virtio :-)
Why not just make a virtio device for this kind of thing?
Regards,
Anthony Liguori
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