----- Original Message ----- > From: "Christoph Hellwig" <hch@xxxxxx> > To: "Federico Simoncelli" <fsimonce@xxxxxxxxxx> > Cc: kvm@xxxxxxxxxxxxxxx, kwolf@xxxxxxxxxx, qemu-devel@xxxxxxxxxx, avi@xxxxxxxxxx > Sent: Thursday, June 16, 2011 4:28:09 PM > Subject: Re: [Qemu-devel] [PATCH] qemu-img: Add cache command line option > On Wed, Jun 15, 2011 at 09:46:10AM -0400, Federico Simoncelli wrote: > > qemu-img currently writes disk images using writeback and filling > > up the cache buffers which are then flushed by the kernel preventing > > other processes from accessing the storage. > > This is particularly bad in cluster environments where time-based > > algorithms might be in place and accessing the storage within > > certain timeouts is critical. > > This patch adds the option to choose a cache method when writing > > disk images. > > Allowing to chose the mode is of course fine, but what about also > choosing a good default? writethrough doesn't really make any sense > for qemu-img, given that we can trivially flush the cache at the end > of the operations. I'd also say that using the buffer cache doesn't > make sense either, as there is little point in caching these > operations. I totally agree with you, I didn't change the default to increase the chances for my patch to be accepted. If we want cache=none as default we can easily change: -#define BDRV_DEFAULT_CACHE "writeback" +#define BDRV_DEFAULT_CACHE "none" -- Federico -- 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
