30.11.2018 18:33, Max Reitz wrote: > On 30.11.18 16:24, Vladimir Sementsov-Ogievskiy wrote: >> 30.11.2018 17:59, Max Reitz wrote: >>> On 30.11.18 15:51, Vladimir Sementsov-Ogievskiy wrote: >>>> 30.11.2018 17:10, Kevin Wolf wrote: >>>>> Am 30.11.2018 um 14:48 hat Vladimir Sementsov-Ogievskiy geschrieben: >>>>>> 30.11.2018 16:13, Max Reitz wrote: >>>>>>> On 30.11.18 14:06, Vladimir Sementsov-Ogievskiy wrote: >>>>>>>> 30.11.2018 15:30, Max Reitz wrote: >>>>>>>>> On 29.11.18 11:18, Vladimir Sementsov-Ogievskiy wrote: >>>>>>>>>> This test is broken without previous commit fixing dead-lock in >>>>>>>>>> mirror. >>>>>>>>>> >>>>>>>>>> Signed-off-by: Vladimir Sementsov-Ogievskiy<vsement...@virtuozzo.com> >>>>>>>>>> --- >>>>>>>>>> tests/qemu-iotests/235 | 59 >>>>>>>>>> ++++++++++++++++++++++++++++++++++++++ >>>>>>>>>> tests/qemu-iotests/235.out | 1 + >>>>>>>>>> tests/qemu-iotests/group | 1 + >>>>>>>>>> 3 files changed, 61 insertions(+) >>>>>>>>>> create mode 100755 tests/qemu-iotests/235 >>>>>>>>>> create mode 100644 tests/qemu-iotests/235.out >>>>>>>>> I'll get to the first patch in a second, but first a suggestion for >>>>>>>>> this >>>>>>>>> patch: I think it's not so good to use 2 GB of space for a test (1 GB >>>>>>>>> for the source, 1 GB for the target). So I tried my luck and found >>>>>>>>> that >>>>>>>>> the test works, too, if you just use preallocation=metadata for the >>>>>>>>> source (instead of actually writing data) and blockdev-mirror'ing the >>>>>>>>> data to a throttled null-co device. >>>>>>>> >>>>>>>> Hmm, so parsing metadata is enough for qcow2 to yield on write, yes? >>>>>>> >>>>>>> Apparently so. If you can confirm that applying those changes to the >>>>>>> test still make it work (i.e., fail before patch 1, pass afterwards), >>>>>>> then I think it is just as good. >>>>>> >>>>>> Ok, I've checked that your changes works for me. >>>>>> >>>>>> hm, but we write to null, so, yield on write comes from throttling, >>>>>> however, >>>>>> without preallocation=metadata, it don't work.., do you know, why we need >>>>>> preallocation to reproduce? >>>>> >>>>> If I should take a guess, probably because mirror only copies allocated >>>>> clusters? >>>>> >>>>> Kevin >>>>> >>>> >>>> hm, so, what preallocation=metadata does? I thought, it preallocates >>>> tables, but all qcow2 clusters would be unallocated.. >>> >>> No, it initializes all metadata structures (i.e., L2 tables) so they >>> point to data clusters; which is why you cannot use it with backing >>> files. It's just that the data clusters are not written. >> >> so, clusters are allocated? in this case, we don't avoid allocating of 1G, >> but only have a performance gain? > > The data isn't written, so less than 1 MB are actually allocated on-disk. > > The L2 tables do point to offsets over a range of 1 GB, but they should > all be holes on the filesystem. > > Max >
Understand, ok, thank you! -- Best regards, Vladimir
