Nir Soffer 186e0057f2 qemu_nbd: Select cache and aio automatically ...

Previously we use --cache=writeback and --aio=threads so we can access
images on file system that does not support direct I/O. This is
sometimes faster than --cache=none and --aio=native, but typically give
less consistent results, and pollute the page cache with image data,
which is mostly likely will never be used.

When uploading and downloading images on a hypervisor, using the page
cache can be harmful and cause sanlock timeouts when the kernel try to
flush huge images to the underlying storage.

Future qemu-img and qemu-nbd are expected to implement "auto" cache and
aio modes, selecting --cache=none and --aio=native if possible. This
change implements this in our qemu_nbd wrapper so we can use this now
with current qemu version.

When starting qemu_nbd.Server(), if cache was not specified, we select
cache="none" if the image can be opened with direct I/O. If aio was not
specified, we select it based on the cache value.

Signed-off-by: Nir Soffer <nsoffer@redhat.com>

2022-03-13 16:34:23 +02:00

..

_internal

qemu_nbd: Select cache and aio automatically

2022-03-13 16:34:23 +02:00

admin

admin: Profiling support

2022-02-14 17:48:08 +02:00

client

qemu_nbd: Select cache and aio automatically

2022-03-13 16:34:23 +02:00

__init__.py

pypi: Eliminate the daemon directory

2021-10-21 19:39:45 +03:00