tor/changes/bug12170
Nick Mathewson ad8977e394 Avoid needless router_dir_info_has_changed from router_set_status
On some profiles of Andrea's from #11332, I found that a great deal
of time can still be attributed to functions called from
update_router_have_minimum_dir_info().  This is making our
digestmap, tor_memeq, and siphash functions take a much bigger
portion of runtime than they really should.

If we're calling update_router_have_minimum_dir_info() too often,
that's because we're calling router_dir_info_changed() too often.
And it looks like most of the callers of router_dir_info_changed()
are coming as tail-calls from router_set_status() as invoked by
channel_do_open_actions().

But we don't need to call router_dir_info_changed() so much!  (I'm
not quite sure we need to call it from here at all, but...) Surely
we don't need to call it from router_set_status when the router's
status has not actually changed.

This patch makes us call router_dir_info_changed() from
router_set_status only when we are changing the router's status.

Fix for bug 12170.  This is leftover from our fix back in 273ee3e81
in 0.1.2.1-alpha, where we started caching the value of
update_router_have_minimum_dir_info().
2014-06-02 00:45:15 -04:00

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o Major bugfixes (performance):
- Do not recompute whether we have sufficient information to build
circuits every time we make a successful connection. Previously,
we would forget our cached value for this flag every time we
successfully opened a channel (or marked a router as running or not
running for any
other reason), regardless of whether we had
previously believed the router to be running. This forced us to
run a fairly expensive update operation with relatively
high frequency.
Fixes bug 12170; bugfix on 0.1.2.1-alpha.