Lower stack chunk size in RTS to reduce thread STACK memory (closes h…

…asura#5190)

This reduces memory consumption for new idle subscriptions significantly
(see linked ticket).

The hypothesis is: we fork a lot of threads per websocket, and some of
these use slightly more than the initial 1K stack size, so the first
overflow balloons to 32K, when significantly less is required.

However: running with `+RTS -K1K -xc` did not seem to show evidence of
any overflows! So it's a mystery why this improves things.

GHC should probably also be doubling the stack buffer at each overflow
or doing something even smarter; the knobs we have aren't so helpful.

server/commit_diff.txt

@@ -162,41 +162,6 @@ Date:   Tue Jun 30 23:53:10 2020 -0400
 
     Also related: #3388 #4077
 
-commit 93104e616f53ed46503577032c9eacf9be31575a
-Merge: 6c689992 1dbe5cd1
-Author: Brandon Simmons <brandon@hasura.io>
-Date:   Fri Jun 26 18:24:53 2020 -0400
-
-    Merge pull request #5214 from jberryman/5190-improve-websockets-idle-memory-v2-only-kc8
-
-    Lower stack chunk size in RTS to reduce thread STACK memory (closes #5190)
-
-commit 1dbe5cd1ab4a68dd2518f9e57a656517f708e900
-Merge: f9b5b838 6c689992
-Author: Brandon Simmons <brandon@hasura.io>
-Date:   Fri Jun 26 15:02:49 2020 -0400
-
-    Merge branch 'master' into 5190-improve-websockets-idle-memory-v2-only-kc8
-
-commit f9b5b8382cbd41a589d1096c720805d3184153d4
-Author: Brandon Simmons <brandon.m.simmons@gmail.com>
-Date:   Tue Jun 23 20:35:36 2020 -0400
-
-    Lower stack chunk size in RTS to reduce thread STACK memory (closes #5190)
-
-    This reduces memory consumption for new idle subscriptions significantly
-    (see linked ticket).
-
-    The hypothesis is: we fork a lot of threads per websocket, and some of
-    these use slightly more than the initial 1K stack size, so the first
-    overflow balloons to 32K, when significantly less is required.
-
-    However: running with `+RTS -K1K -xc` did not seem to show evidence of
-    any overflows! So it's a mystery why this improves things.
-
-    GHC should probably also be doubling the stack buffer at each overflow
-    or doing something even smarter; the knobs we have aren't so helpful.
-
 (Done, but we should re-visit this, if we do query plan caching)
 commit 20cbe9cfd3e90b91d3f4faf370b081fc3859cbde
 Author: Auke Booij <auke@hasura.io>