cborutil: change buffering strategy
Profiling revealed that we were spending a lot of time on the
line that was concatenating the old buffer with the incoming data
when attempting to decode long byte strings, such as manifest
revisions.
Essentially, we were feeding N chunks of size len(X) << len(Y) into
decode() and continuously allocating a new, larger buffer to hold
the undecoded input. This created substantial memory churn and
slowed down execution.
Changing the code to aggregate pending chunks in a list until we
have enough data to fully decode the next atom makes things much
more efficient.
I don't have exact data, but I recall the old code spending >1s
on manifest fulltexts from the mozilla-unified repo. The new code
doesn't significantly appear in profile output.
Differential Revision: https://phab.mercurial-scm.org/D4854
workingfilectx.date = (1000, 0)
ASCII : Gr?ezi!
Latin-1 : Grüezi!
UTF-8 : Grüezi!
<status modified=['foo'], added=[], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
diff --git a/foo b/foo
--- a/foo
+++ b/foo
@@ -1,1 +1,2 @@
foo
+bar
= checking context.status():
== checking workingctx.status:
wctx._status=<status modified=['bar-m'], added=['bar-a'], removed=['bar-r'], deleted=[], unknown=[], ignored=[], clean=[]>
=== with "pattern match":
<status modified=['bar-m'], added=[], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
wctx._status=<status modified=['bar-m'], added=['bar-a'], removed=['bar-r'], deleted=[], unknown=[], ignored=[], clean=[]>
<status modified=[], added=['bar-m'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
wctx._status=<status modified=['bar-m'], added=['bar-a'], removed=['bar-r'], deleted=[], unknown=[], ignored=[], clean=[]>
=== with "always match" and "listclean=True":
<status modified=['bar-m'], added=['bar-a'], removed=['bar-r'], deleted=[], unknown=[], ignored=[], clean=['foo']>
wctx._status=<status modified=['bar-m'], added=['bar-a'], removed=['bar-r'], deleted=[], unknown=[], ignored=[], clean=[]>
<status modified=[], added=['bar-a', 'bar-m'], removed=[], deleted=[], unknown=[], ignored=[], clean=['foo']>
wctx._status=<status modified=['bar-m'], added=['bar-a'], removed=['bar-r'], deleted=[], unknown=[], ignored=[], clean=[]>
== checking workingcommitctx.status:
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
=== with "always match":
<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
<status modified=[], added=['bar-a', 'bar-m', 'bar-r'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
=== with "always match" and "listclean=True":
<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=['bar-r', 'foo']>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
<status modified=[], added=['bar-a', 'bar-m', 'bar-r'], removed=[], deleted=[], unknown=[], ignored=[], clean=['foo']>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
=== with "pattern match":
<status modified=['bar-m'], added=[], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
<status modified=[], added=['bar-m'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
=== with "pattern match" and "listclean=True":
<status modified=[], added=[], removed=[], deleted=[], unknown=[], ignored=[], clean=['bar-r', 'foo']>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
<status modified=[], added=['bar-r'], removed=[], deleted=[], unknown=[], ignored=[], clean=['foo']>
wcctx._status=<status modified=['bar-m'], added=['bar-a'], removed=[], deleted=[], unknown=[], ignored=[], clean=[]>
== commit with manifestlog invalidated
commit 1: 2efe531a913fa648867ab8824360371679d05a65
commit 2: 2caca91f6362020334384ebe27bae67315298abf
commit 3: abd6b0f49f338be22b094ef2b7425e8048f8337b