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libplugin: remove redundant destructor which causes exponential slowdown on large numbers of requests.

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Note that we create a destructor on the command to reset request->cmd
pointer if the cmd is freed (so we know not to call the callback).
But attaching hundreds of thousands of them is slow: it's a
single-linked list, which is iterated in several places.

But that's redundant: the request is now allocated off the cmd, so freeing the command
will free the request anyway.

Hacking in something to print progress to a file, here's the number of
requests processed every 10 seconds before and after:

Before:
	$ while sleep 10; do wc -l /tmp/bkpr-progress; done
	181529 /tmp/bkpr-progress
	195994 /tmp/bkpr-progress
	207083 /tmp/bkpr-progress
	226336 /tmp/bkpr-progress
	234319 /tmp/bkpr-progress
	241514 /tmp/bkpr-progress
	247421 /tmp/bkpr-progress
	255292 /tmp/bkpr-progress
	261367 /tmp/bkpr-progress
	269085 /tmp/bkpr-progress
	276953 /tmp/bkpr-progress
	282233 /tmp/bkpr-progress
	286193 /tmp/bkpr-progress
	290930 /tmp/bkpr-progress
	295276 /tmp/bkpr-progress
	301086 /tmp/bkpr-progress

After:
	169505 /tmp/bkpr-progress
	196010 /tmp/bkpr-progress
	219370 /tmp/bkpr-progress
	235671 /tmp/bkpr-progress
	244242 /tmp/bkpr-progress
	255362 /tmp/bkpr-progress
	265636 /tmp/bkpr-progress
	276966 /tmp/bkpr-progress
	284451 /tmp/bkpr-progress
	288836 /tmp/bkpr-progress
	296578 /tmp/bkpr-progress
	304571 /tmp/bkpr-progress

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2025-10-17 23:09:48 +10:30
committed by Sangbida Chaudhuri
parent 7b1c4874ed
commit b7c2629d0e
1 changed files with 0 additions and 25 deletions
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25
plugins/libplugin.c
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@@ -290,17 +290,6 @@ static void ld_rpc_send(struct plugin *plugin, struct json_stream *stream)
io_wake(plugin->io_rpc_conn);
}
/* When cmd for request is gone, we use this as noop callback */
static struct command_result *ignore_cb(struct command *command,
const char *method,
const char *buf,
const jsmntok_t *result,
void *arg)
{
return &complete;
}
/* Ignore the result, and terminate the timer/aux/hook */
struct command_result *ignore_and_complete(struct command *cmd,
const char *method,
@@ -357,14 +346,6 @@ struct command_result *plugin_broken_cb(struct command *cmd,
json_tok_full(buf, result));
}
static void disable_request_cb(struct command *cmd, struct out_req *out)
{
out->errcb = NULL;
out->cb = ignore_cb;
/* Called because cmd got free'd */
out->cmd = NULL;
}
/* Prefix is usually a cmd->id */
static const char *json_id(const tal_t *ctx, struct plugin *plugin,
const char *method, const char *prefix)
@@ -424,9 +405,6 @@ jsonrpc_request_start_(struct command *cmd,
strmap_add(&cmd->plugin->out_reqs, out->id, out);
tal_add_destructor2(out, destroy_out_req, cmd->plugin);
/* If command goes away, don't call callbacks! */
tal_add_destructor2(out->cmd, disable_request_cb, out);
out->js = new_json_stream(NULL, cmd, NULL);
json_object_start(out->js, NULL);
json_add_string(out->js, "jsonrpc", "2.0");
@@ -1100,9 +1078,6 @@ static void handle_rpc_reply(struct plugin *plugin, const char *buf, const jsmnt
return;
}
/* Remove destructor if one existed */
tal_del_destructor2(out->cmd, disable_request_cb, out);
/* We want to free this if callback doesn't. */
tal_steal(tmpctx, out);