phases: rework the logic of _pushdiscoveryphase to bound complexity This rework the various graph traversal in _pushdiscoveryphase to keep the complexity in check. This is done though a couple of things: - first, limiting the space we have to explore, for example, if we are not in publishing push, we don't need to consider remote draft roots that are also draft locally, as there is nothing to be moved there. - avoid unbounded descendant computation, and use the faster "rev between" computation. This provide a massive boost to performance when exchanging with repository with a massive amount of draft, like mozilla-try: ### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog # benchmark.name = hg.command.push # bin-env-vars.hg.flavor = default # bin-env-vars.hg.py-re2-module = default # benchmark.variants.explicit-rev = all-out-heads # benchmark.variants.issue6528 = disabled # benchmark.variants.protocol = ssh # benchmark.variants.reuse-external-delta-parent = default ## benchmark.variants.revs = any-1-extra-rev before: 20.346590 seconds after: 11.232059 seconds (-38.15%, -7.48 seconds) ## benchmark.variants.revs = any-100-extra-rev before: 24.752051 seconds after: 15.367412 seconds (-37.91%, -9.38 seconds) After this changes, the push operation is still quite too slow. Some of this can be attributed to general phases slowness (reading all the roots from disk for example) and other know slowness (not using persistent-nodemap, branchmap, tags, etc. We are also working on them, but with this series, phase discovery during push no longer showing up in profile and this is a pretty nice and bit low-hanging fruit out of the way. ### (same case as the above) # benchmark.variants.revs = any-1-extra-rev pre-%ln-change: 44.235070 this-changeset: 11.232059 seconds (-74.61%, -33.00 seconds) # benchmark.variants.revs = any-100-extra-rev pre-%ln-change: 49.234697 this-changeset: 15.367412 seconds (-68.79%, -33.87 seconds) Note that with this change, the `hg push` performance is now much closer to the `hg pull` performance, even it still lagging behind a bit. (and the overall performance are still too slow). ### data-env-vars.name = mozilla-try-2023-03-22-ds2-pnm # benchmark.variants.explicit-rev = all-out-heads # benchmark.variants.issue6528 = disabled # benchmark.variants.protocol = ssh # benchmark.variants.pulled-delta-reuse-policy = default # bin-env-vars.hg.flavor = rust ## benchmark.variants.revs = any-1-extra-rev hg.command.pull: 6.517450 hg.command.push: 11.219888 ## benchmark.variants.revs = any-100-extra-rev hg.command.pull: 10.160991 hg.command.push: 14.251107 ### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog # bin-env-vars.hg.py-re2-module = default # benchmark.variants.explicit-rev = all-out-heads # benchmark.variants.issue6528 = disabled # benchmark.variants.protocol = ssh # benchmark.variants.pulled-delta-reuse-policy = default ## bin-env-vars.hg.flavor = default ## benchmark.variants.revs = any-1-extra-rev hg.command.pull: 8.577772 hg.command.push: 11.232059 ## bin-env-vars.hg.flavor = default ## benchmark.variants.revs = any-100-extra-rev hg.command.pull: 13.152976 hg.command.push: 15.367412 ## bin-env-vars.hg.flavor = rust ## benchmark.variants.revs = any-1-extra-rev hg.command.pull: 8.731982 hg.command.push: 11.178751 ## bin-env-vars.hg.flavor = rust ## benchmark.variants.revs = any-100-extra-rev hg.command.pull: 13.184236 hg.command.push: 15.620843

--- a/mercurial/exchange.py	Fri Apr 05 22:47:44 2024 +0200
+++ b/mercurial/exchange.py	Tue Apr 09 02:54:19 2024 +0200
@@ -621,8 +621,10 @@
 
     (computed for both success and failure case for changesets push)"""
     outgoing = pushop.outgoing
-    unfi = pushop.repo.unfiltered()
-    to_rev = unfi.changelog.index.rev
+    repo = pushop.repo
+    unfi = repo.unfiltered()
+    cl = unfi.changelog
+    to_rev = cl.index.rev
     remotephases = listkeys(pushop.remote, b'phases')
 
     if (
@@ -644,42 +646,43 @@
         pushop.fallbackoutdatedphases = []
         return
 
-    fallbackheads_rev = [to_rev(n) for n in pushop.fallbackheads]
-    futureheads_rev = [to_rev(n) for n in pushop.futureheads]
-
+    fallbackheads_rev = {to_rev(n) for n in pushop.fallbackheads}
     pushop.remotephases = phases.RemotePhasesSummary(
         pushop.repo,
         fallbackheads_rev,
         remotephases,
     )
-    droots = pushop.remotephases.draft_roots
-
-    extracond = b''
-    if not pushop.remotephases.publishing:
-        extracond = b' and public()'
-    revset = b'heads((%%ld::%%ld) %s)' % extracond
-    # Get the list of all revs draft on remote by public here.
-    # XXX Beware that revset break if droots is not strictly
-    # XXX root we may want to ensure it is but it is costly
-    fallback = list(unfi.set(revset, droots, fallbackheads_rev))
-    if not pushop.remotephases.publishing and pushop.publish:
-        future = list(
-            unfi.set(
-                b'%ld and (not public() or %ld::)', futureheads_rev, droots
-            )
-        )
-    elif not outgoing.missing:
-        future = fallback
+    droots = set(pushop.remotephases.draft_roots)
+
+    fallback_publishing = pushop.remotephases.publishing
+    push_publishing = pushop.remotephases.publishing or pushop.publish
+    missing_revs = {to_rev(n) for n in outgoing.missing}
+    drafts = unfi._phasecache.get_raw_set(unfi, phases.draft)
+
+    if fallback_publishing:
+        fallback_roots = droots - missing_revs
+        revset = b'heads(%ld::%ld)'
     else:
-        # adds changeset we are going to push as draft
-        #
-        # should not be necessary for publishing server, but because of an
-        # issue fixed in xxxxx we have to do it anyway.
-        missing_rev = [to_rev(n) for n in outgoing.missing]
-        fdroots = list(unfi.set(b'roots(%ld  + %ld::)', missing_rev, droots))
-        fdroots = [f.rev() for f in fdroots]
-        future = list(unfi.set(revset, fdroots, futureheads_rev))
-    pushop.outdatedphases = future
+        fallback_roots = droots - drafts
+        fallback_roots -= missing_revs
+        # Get the list of all revs draft on remote but public here.
+        revset = b'heads((%ld::%ld) and public())'
+    if not fallback_roots:
+        fallback = fallback_rev = []
+    else:
+        fallback_rev = unfi.revs(revset, fallback_roots, fallbackheads_rev)
+        fallback = [repo[r] for r in fallback_rev]
+
+    if push_publishing:
+        published = missing_revs.copy()
+    else:
+        published = missing_revs - drafts
+    if pushop.publish:
+        published.update(fallbackheads_rev & drafts)
+    elif fallback:
+        published.update(fallback_rev)
+
+    pushop.outdatedphases = [repo[r] for r in cl.headrevs(published)]
     pushop.fallbackoutdatedphases = fallback