BBlack has uploaded a new change for review.
https://gerrit.wikimedia.org/r/295376
Change subject: caches: tcp_notsent_lowat => 128K
......................................................................
caches: tcp_notsent_lowat => 128K
tested manually on cp1065, no apparent huge negative effects on
system perf (so probably at worst, this is merely ineffective due
to nginx polling/writing strategy, at best it's a nice win for
client perf on average).
Change-Id: I548d86c716aa84ec20c54bbaedfd6de2aff09902
---
M modules/role/manifests/cache/perf.pp
1 file changed, 17 insertions(+), 0 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/operations/puppet
refs/changes/76/295376/1
diff --git a/modules/role/manifests/cache/perf.pp
b/modules/role/manifests/cache/perf.pp
index aeecbd6..219dfba 100644
--- a/modules/role/manifests/cache/perf.pp
+++ b/modules/role/manifests/cache/perf.pp
@@ -68,4 +68,21 @@
sysctl::parameters { 'tw_reuse':
values => { 'net.ipv4.tcp_tw_reuse' => 1 },
}
+
+ # tcp_notsent_lowat:
+ # Default is -1 (unset). Setting this changes TCP sockets' writeability
+ # behavior. The default behavior is to keep the socket writeable until the
+ # whole socket buffer fills. With this set, even if there's buffer space,
+ # the kernel doesn't notify of writeability (e.g. via epoll()) until the
+ # amount of unsent data (as opposed to unacked) in the socket buffer is
+ # less than this value. This reduces local buffer bloat on our server's
+ # sending side, which may help with HTTP/2 prioritization. The magic value
+ # for tuning is debateable, but arguably even setting a conservative
+ # (higher) value here is better than not setting it all, in almost all
+ # cases for any kind of TCP traffic. ~128K seems to be a common
+ # recommendation for something close-ish to optimal for internet-facing
+ # things.
+ sysctl::parameters { 'tcp_notsent_lowat':
+ values => { 'net.ipv4.tcp_notsent_lowat' => 131072 },
+ }
}
--
To view, visit https://gerrit.wikimedia.org/r/295376
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: I548d86c716aa84ec20c54bbaedfd6de2aff09902
Gerrit-PatchSet: 1
Gerrit-Project: operations/puppet
Gerrit-Branch: production
Gerrit-Owner: BBlack <bbl...@wikimedia.org>
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