We were blocking for easily 1/10 or 1/5 of a second in fdatasync(),
which drastically slows down the whole process.
This threading isn't quite as good as the ostree-pull command, but it
lets us avoid the dependency on libsoup everywhere, and it's simpler.
After a while of pull-deploy cycles, you start to accumulate a lot of
them. While the deployment read-only part is hardlinked, the -etc
space adds up.
Additionally, the repository itself just gets large.
The new command "ostree admin prune" deletes everything except the
"current" and "previous" deployments.
The previous code (unintentionally) only traversed from refs; so data
only reachable from previous commits would be deleted. That shouldn't
be the default, but we do want to offer it as an option.
So add a --refs-only option.
This seems to work around a likely Linux kernel VFS bug, where I
randomly see ENOENT on link() when we *definitely* called mkdir() at
an earlier point in time.
This is an incompatible change to archive-z, thus it is now renamed to
archive-z2 and ostree will no longer parse archive-z.
I noticed in perf that we were spending some time zlib-decompressing
file headers, which is just inefficient. Rather than do this, keep
the headers uncompressed, and just zlib-compress content.
This gives us something closer to the advantages of archive and
archive-z when using the latter. Concretely we get deduplication
among multiple checkouts, along with the "devino" hash table trick
during commits to avoid checksumming content again.
This is enabled by default.
For similar reasons as metadata, this avoids having the main thread
blocked in fdatasync(), and even better - we can achieve much higher
parallelism if we have multiple threads blocked on fdatasync().
We need this hack for "archive mode" repositories; otherwise,
what ends up happening is that we get 10000+ requests pending
for .filemeta files, which we can't process until we also get
the .filecontent.
Note this hack is unneccessary when fetching from archive-z
repositories.
Create a worker thread for processing metadata, reserving the main
thread for HTTP requests.
This can create a very significant efficiency win for large pull
requests since we are much more likely to keep a full pipeline open.
The status display is also nicer now.
This is where loose content objects are stored as one compressed file,
instead of the two separate ones for regular archive mode. This mode
would be suitable for HTTP servers, beause only one HTTP request is
necessary, and the result would be compressed.
Cleanly separate metadata/content APIs, rather than defaulting to
raw streams. This helps most use cases.
Also, drop support for staging content without knowing the total
length. This complicated the code, and for things like streaming
HTTP, we should be able to figure this out from Content-Length.
They're not a large efficiency win at the moment, because we don't
do any delta compression.
At the moment, they simply served to compress data, but we will change
the archive mode to do that by default.
First, move deployments to /ostree/deploy. Having them in the
toplevel clutters the filesystem layout too much.
When we deploy a tree like /ostree/deploy/NAME, there is now also a
writable directory /ostree/deploy/NAME-etc. This is mounted as
read-write inside the system.
On an initial install, that directory is copied from
/ostree/deploy/NAME/etc. On subsequent deployments, we find any
changes made in the current deployment's /etc, and apply that set of
changes to the new deployment's /etc.
See https://live.gnome.org/OSTree/EverythingInEtcIsABug
I run builds on my laptop, but it also crashes about 1/4 of the time
while suspending. It's definitely undesrirable to get e.g. empty
.dirtree objects because they corrupt builds. Concretely, I was
getting empty contents committed for xorg-util-macros.
Now, we used to write out temporary files using g_file_replace() which
does a fsync() during close, but then switched to a more "manual"
g_file_append_to().
We could switch back to g_file_replace(), but the problem is, we don't
want to call fsync() on temporary files in the case where we already
have the object. Attempting to add an object we already have is a
*very* common case.
This is both the old and new code sequence for the case where an
object is already stored:
open(temp, O_WRONLY)
write() write() write()
close()
lstat(objects/3a/9fe332...) = 0
unlink(temp)
In the *new* code, here's the case where an object *isn't* stored:
open(temp, O_WRONLY)
write() write() write()
close()
lstat(objects/3a/9fe332...) = -1
open(temp, O_RDONLY)
fdatasync()
close()
rename(temp, objects/3a/9fe332)
Compare with the *old* code path for when an object isn't stored:
open(temp, O_WRONLY)
write() write() write()
close()
lstat(objects/3a/9fe332...) = -1
link(temp, objects/3a/9fe332)
unlink(temp)
The problem with this is we really need to fdatasync(). Also doing
just rename() instead of the weird link()/unlink() helps us express to
the filesystem that we want atomic semantics. For example, BTRFS has
special handling for rename().
We really don't have a sane story for private files. This is a
defensive step ensuring that with old versions of gnome-ostree,
components that mistakenly have un-world-readable files don't break
pulls.
Colin Walters