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Merge remote-tracking branch 'origin/topic/arne.welzel/fix-poll-interval-is-live'

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* origin/topic/arne.welzel/fix-poll-interval-is-live:
  iosource/Manager: Fix poll_interval updating using not-yet valid IsLive()
This commit is contained in:
Tim Wojtulewicz 2023-04-12 13:23:29 -07:00
commit 6ac72a31bf
4 changed files with 37 additions and 3 deletions
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26
CHANGES
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@ -1,3 +1,29 @@
6.0.0-dev.353 | 2023-04-12 13:23:29 -0700
* iosource/Manager: Fix poll_interval updating using not-yet valid IsLive() (Arne Welzel, Corelight)
Testing io_poll_interval_live tweaks with @dopheide-esnet on a Myricom based
system to reduce CPU usage showed no visible effect.
It turns out, the pkt_src->IsLive() call used to update poll_interval is only
valid *after* calling ->Register() with the source. The conditional updating
of the poll_interval introduced in 4fa3e4b9b4d78e6f20f42b9dbd85216403be07db
never worked out how it was intended to.
The fix ensures that
* we actually use a poll_interval of 10 in the live case
* changing io_poll_interval_live does have an effect
This is a bit of a major change due to lowering the default poll_interval
by a magnitude, but that seemed to have been the intention always. It's also
tunable via redef, so worst case it can be adapted via configuration.
As reference, with the default a Pcap::non_fd_timeout of 20usec *and* a
poll_interval of 100, theoretically we'd be trying to ask a non-selectable
packet source 500000 per second for a new packet. This is not a likely packet
rate that a single worker would currently observe or manage to process.
6.0.0-dev.350 | 2023-04-11 15:41:31 -0700 6.0.0-dev.350 | 2023-04-11 15:41:31 -0700
* Only use -Wno-changes-meaning if it exists (Tim Wojtulewicz, Corelight) * Only use -Wno-changes-meaning if it exists (Tim Wojtulewicz, Corelight)

4
NEWS
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@ -191,6 +191,10 @@ Changed Functionality
processing input. Specifically in zeek -r scenarios, that is not the wanted processing input. Specifically in zeek -r scenarios, that is not the wanted
behaviour. behaviour.
- The IO loop's poll interval is now correctly reduced from 100 to 10 for
live packet sources. This should lower CPU usage for deployments with
non-selectable packet sources.
Removed Functionality Removed Functionality
--------------------- ---------------------

2
VERSION
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@ -1 +1 @@
6.0.0-dev.350 6.0.0-dev.353

8
src/iosource/Manager.cc
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@ -402,12 +402,16 @@ void Manager::Register(PktSrc* src)
{ {
pkt_src = src; pkt_src = src;
Register(src, false);
// Once we know if the source is live or not, adapt the
// poll_interval accordingly.
//
// Note that src->IsLive() is only valid after calling Register().
if ( src->IsLive() ) if ( src->IsLive() )
poll_interval = BifConst::io_poll_interval_live; poll_interval = BifConst::io_poll_interval_live;
else if ( run_state::pseudo_realtime ) else if ( run_state::pseudo_realtime )
poll_interval = 1; poll_interval = 1;
Register(src, false);
} }
static std::pair<std::string, std::string> split_prefix(std::string path) static std::pair<std::string, std::string> split_prefix(std::string path)