Askrene parallel solving support#8723
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rustyrussell wants to merge 19 commits intoElementsProject:masterfrom
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Askrene parallel solving support#8723rustyrussell wants to merge 19 commits intoElementsProject:masterfrom
rustyrussell wants to merge 19 commits intoElementsProject:masterfrom
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Very clever parallelization!
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…g an entore response. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We reimplemented this redundantly: hash_scid was called short_channel_id_hash, so I obviously missed it. Rename, and implement hash_scidd helper too. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is fairly simple. We do all the prep work, fire off the child, and it continues all the way to producing JSON output (or an error). The parent then forwards it. Limitations (fixed in successive patches): 1. Child logging currently gets lost. 2. We wait for the child, so this code is not a speedup. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We just shim rq_log for now, but we'll be weaning the child process off that soon. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We want to make it clear when future generations edit the code, which routines are called in the child (i.e. all the routing), and which in the parent. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Weird that it was in askrene.c Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Now there's only one file clearly shared by both parent and child. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Notably no access to the struct command and struct plugin. Note: we actually *do* mess with askrene->reserves, but the previous code used cmd to get to it. Now we need to include a non-const pointer in struct route_query. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: Plugins: `askrene` now runs routing in parallel. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Queue them before we query local channels, so they don't use stale information. Changelog-Added: Config: `askrene-max-threads` to control how many CPUs we use for routing (default 4). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
The fork logic itself is pretty simple, so do that directly in askrene.c, and then call into "run_child()" almost as soon as we do the fork. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This makes sure it cannot interfere with the parent askrene's connection to lightningd, for example. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This speeds them up, and exercises the askrene parallel code. Before: test_real_data: 260s test_real_biases: 173s After: test_real_data: 133s test_real_biases: 106s And this is because much of the time is spent uncompressing the gossmap and startup. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
I noticed this in the logs: ``` lightningd-1 2026-01-28T00:27:37.504Z DEBUG gossipd: gossip_store: Read 59428/118856/0/0 cannounce/cupdate/nannounce/delete from store in 45521871 bytes, now 45521849 bytes (populated=true) lightningd-1 2026-01-28T00:27:37.504Z DEBUG gossipd: Got 118856 bad cupdates, ignoring them (expected on mainnet) ``` That's weird, and turns out it counting good updates, not bad ones! Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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This is actually fairly simple: we fork() at the point we're going to call the solver, and the child runs until it either produces an error message or a JSON result.
The main changes are in refactoring to make it clear which parts of the code run in the child, and which run in the parent.