[libvirt] [PATCH 0/2] speed up qemu domain save by increasing dd blocksize

These two patches are posted together because applying the 2nd exposes the bug fixed by the first. Here are the results of tests I made with various block sizes before deciding the 1MB really was the best balance (all tests were done on a paused 512MB domain, saving to local disk on a Lenovo T61 laptop) BS M:SS save image size ----- ---- --------------- 2048K - 0:56 476135451 1024K - 0:56 475090953 512k - 1:02 474564173 256k - 1:10 474303797 128k - 1:25 474176859 512 - 3:47 474085423 - the original I didn't bother testing sizes between 512 and 128k, as there was still significant improvement from 128k to 256k.