mirror of https://gitlab.com/ita1024/waf.git
Example of optimizations for partial builds
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Thomas Nagy
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#! /usr/bin/env python
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# encoding: utf-8
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# Thomas Nagy, 2017 (ita)
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"""
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A system for fast partial rebuilds
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Creating a large amount of task objects up front can take some time.
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By making a few assumptions, it is possible to avoid posting creating
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task objects for targets that are already up-to-date
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On a silly benchmark the gain observed for 20000 tasks can be 5s->1s for
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a single file change.
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Assuptions:
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* Mostly for C/C++/Fortran targets with link tasks (object-only targets are not handled)
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* This is only for full project builds, so this does not interfere with --targets
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* Building from a subfolder does not prune targets from that folder
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* The installation phase is ignored
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* `use=` dependencies are fully specified up front even across build groups
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* Files are not modified while building
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"""
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import os
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from waflib import Build, Context, Errors, Logs, Task, Utils
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from waflib.TaskGen import feature, after_method, taskgen_method
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DONE = 0
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DIRTY = 1
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NEEDED = 2
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class bld(Build.BuildContext):
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def store(self):
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if self.producer.dirty:
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# For each task generator, record all files involved in task objects
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# optimization: done only if there was something built
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for g in self.groups:
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for tg in g:
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do_cache = False
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for tsk in tg.tasks:
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if tsk.hasrun == Task.SUCCESS:
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do_cache = True
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pass
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elif tsk.hasrun == Task.SKIPPED:
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pass
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else:
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# dependencies are incomplete, clear the cache
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try:
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del self.raw_deps[(tg.path.abspath(), tg.idx)]
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except KeyError:
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pass
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break
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else:
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wscript_time = os.stat(tg.path.abspath()).st_mtime
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if not do_cache:
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try:
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cache = self.raw_deps[(tg.path.abspath(), tg.idx)]
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except KeyError:
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# probably cleared because a wscript file changed
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do_cache = True
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else:
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cache[0] = wscript_time
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if do_cache:
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cache = self.raw_deps[(tg.path.abspath(), tg.idx)] = [wscript_time]
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st = set()
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for tsk in tg.tasks:
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st.update(tsk.inputs)
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st.update(self.node_deps.get(tsk.uid(), []))
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cache += sorted(x.abspath() for x in st)
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return Build.BuildContext.store(self)
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def compute_needed_tgs(self):
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# assume the 'use' keys are not modified during the build phase
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# 1. obtain task generators that contain rebuilds
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stales = set()
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for g in self.groups:
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for tg in g:
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if tg.is_stale():
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stales.add(tg)
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reverse_use_map = Utils.defaultdict(list)
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use_map = Utils.defaultdict(list)
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# 2. obtain the 'use' graph and its dual
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for g in self.groups:
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for tg in g:
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try:
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lst = tg.use = Utils.to_list(tg.use)
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except AttributeError:
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pass
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else:
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for x in lst:
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try:
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xtg = self.get_tgen_by_name(x)
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except Errors.WafError:
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pass
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else:
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use_map[tg].append(xtg)
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reverse_use_map[xtg].append(tg)
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# 3. dfs to post downstream tg as stale
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visited = set()
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def mark_down(tg):
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if tg in visited:
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return
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visited.add(tg)
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Logs.debug('rev_use: marking down %r as stale', tg.name)
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tg.staleness = DIRTY
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for x in reverse_use_map[tg]:
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mark_down(x)
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for tg in stales:
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mark_down(tg)
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# 4. dfs to find ancestors tg to mark as needed
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self.needed_tgs = needed_tgs = set()
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def mark_needed(tg):
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if tg in needed_tgs:
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return
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needed_tgs.add(tg)
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if tg.staleness == DONE:
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Logs.debug('rev_use: marking up %r as needed', tg.name)
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tg.staleness = NEEDED
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for x in use_map[tg]:
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mark_needed(x)
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for xx in visited:
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mark_needed(xx)
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# so we have the whole tg trees to post in the set "needed"
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# the stale ones should be fully build, while the needed ones
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# may skip a few tasks, see create_compiled_task and apply_link_after below
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Logs.debug('rev_use: amount of needed task gens: %r', len(needed_tgs))
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def post_group(self):
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# assumption: we can ignore the folder/subfolders cuts
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def tgpost(tg):
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try:
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f = tg.post
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except AttributeError:
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pass
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else:
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f()
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if not self.targets or self.targets == '*':
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for tg in self.groups[self.current_group]:
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# this can cut quite a lot of tg objects
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if tg in self.needed_tgs:
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tgpost(tg)
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else:
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# default implementation
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return Build.BuildContext.post_group()
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def get_build_iterator(self):
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if not self.targets or self.targets == '*':
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self.compute_needed_tgs()
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return Build.BuildContext.get_build_iterator(self)
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@taskgen_method
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def is_stale(self):
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# assume no globs
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self.staleness = DIRTY
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db = os.path.join(self.bld.variant_dir, Context.DBFILE)
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try:
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dbstat = os.stat(db).st_mtime
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except OSError:
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return True
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# 1. check if the configuration changed
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if os.stat(self.bld.bldnode.find_node('c4che').abspath()).st_mtime > dbstat:
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Logs.debug('rev_use: must post %r because the configuration has changed', self.name)
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return True
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# 2. check if this is the first build (no cache)
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try:
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lst = self.bld.raw_deps[(self.path.abspath(), self.idx)]
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except KeyError:
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Logs.debug('rev_use: must post %r because there is no cached data', self.name)
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return True
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# 3. check if the wscript file changed from the previous dep storage
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# assume that the folder timestamp reflects the wscript state
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folder_tstamp = os.stat(self.path.abspath()).st_mtime
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if folder_tstamp != lst[0]:
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Logs.debug('rev_use: must post %r because the tg definition may have changed', self.name)
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return True
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# 4. check the timestamp of dependency files listed are not newer than the last build
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# assume that a file is not modified during a build ~
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def tstamp(x):
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# do some caching
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try:
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cache = self.bld.cache_tstamp_rev_use
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except AttributeError:
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cache = self.bld.cache_tstamp_rev_use = {}
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try:
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return cache[x]
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except KeyError:
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ret = cache[x] = os.stat(x).st_mtime
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return ret
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for x in lst[1:]:
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try:
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ts = tstamp(x)
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except OSError:
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self.bld.raw_deps[(self.path.abspath(), self.idx)] = [folder_tstamp]
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Logs.debug('rev_use: must post %r because %r does not exist anymore', self.name, x)
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return True
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else:
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if ts > dbstat:
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Logs.debug('rev_use: must post %r because %r is newer than the db file', self.name, x)
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return True
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self.staleness = DONE
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return False
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@taskgen_method
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def create_compiled_task(self, name, node):
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if self.staleness == NEEDED:
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return None
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out = '%s.%d.o' % (node.name, self.idx)
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task = self.create_task(name, node, node.parent.find_or_declare(out))
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try:
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self.compiled_tasks.append(task)
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except AttributeError:
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self.compiled_tasks = [task]
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return task
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@feature('c', 'cxx', 'd', 'fc', 'asm')
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@after_method('apply_link')
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def apply_link_after(self):
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if self.staleness != NEEDED:
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return
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try:
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link_task = self.link_task
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except AttributeError:
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pass
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else:
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link_task.hasrun = Task.SKIPPED
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