net: Skip cs_main when a peer has no orphan work #36445

pull w0xlt wants to merge 1 commits into bitcoin:master from w0xlt:net/orphan-check-without-cs-main changing 2 files +38 −0

w0xlt commented at 2:18 AM on October 6, 2026: contributor

ProcessMessages takes cs_main for every peer on every handler pass, just to check for orphan transactions to reconsider, though most peers have none. This PR checks for orphan work under m_tx_download_mutex first and skips cs_main when there is none. Peers with orphan work take the same path as before, plus one uncontended lock.

This removes needless cs_main contention with validation, RPC and wallet threads. It's part of a broader effort to reduce cs_main contention in net processing (see #36244 for context), but stands on its own.

ProcessMessages handling a ping master this PR

no contention 0.005 ms 0.005 ms

another thread holds cs_main for 50 ms 50.1 ms 0.02 ms

Release builds, median of 3 runs. SendMessages in the same handler pass still takes cs_main.

Tested by process_messages_without_orphan_work, which fails without this change.

`ProcessMessages` handling a `ping`	master	this PR
no contention	0.005 ms	0.005 ms
another thread holds `cs_main` for 50 ms	50.1 ms	0.02 ms

net: Skip cs_main when a peer has no orphan work

ProcessMessages reconsiders a peer's orphan transactions before taking
its next message, and took cs_main for this even when the peer had
none. Check for orphan work under m_tx_download_mutex first, so that a
message from a peer without orphan work does not wait for a busy
chainstate.

Test that ProcessMessages completes for such a peer while cs_main is
held.

6549bb4bd6

DrahtBot added the label P2P on Oct 6, 2026
DrahtBot commented at 2:18 AM on October 6, 2026: contributor


The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.



External sites
- Code coverage & benchmarks: https://corecheck.dev/bitcoin/bitcoin/pulls/36445
- Ralph review <img src=https://review.fish.foo/assets/bitcoin/bitcoin/36445.png alt="Ralph review status"> https://git.fish.foo/bitcoin/bitcoin/pulls/36445#author-ralph


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instagibbs commented at 11:33 AM on October 6, 2026: member

I think these kind of refactors only make sense if/when #36244 is an accepted goal by the project

I have not actually looked, just noting for this PR's sake.
w0xlt commented at 3:47 PM on October 6, 2026: contributor

This PR stands on its own, though: skipping cs_main when a peer has no orphan work helps on master today, with or without #36244. #36244 just benefits more from it.
w0xlt commented at 5:41 AM on October 7, 2026: contributor

PR description updated for greater clarity.

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#36244 validation, net: Process blocks asynchronously and reduce cs_main contention

net: Skip cs_main when a peer has no orphan work #36445

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