linux-cachyos-rc: Disable dynamic preemption

By observing a few results, it is observed that dynamic preemption can somehow blur the results between the various preemption models. One example is [1] where there seems to be a 5% difference in throughput between voluntary vs full with dynamic preemption disabled but then the difference goes to a measly 0.6% when dynamic preemption is enabled. I've also been able to reproduce this behaviour across various benchmarks, one of them shared in [2]. Due to that, let's disable dynamic preemption for all kernel configurations (or atleast the default) [1] https://lore.kernel.org/all/[email protected]/ [2] #339 Signed-off-by: Eric Naim <[email protected]>
CachyOS · Jan 6, 2025 · ed8597f · ed8597f
1 parent 9665091
commit ed8597f
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diff --git a/linux-cachyos-rc/.SRCINFO b/linux-cachyos-rc/.SRCINFO
@@ -28,7 +28,7 @@ pkgbase = linux-cachyos-rc
 	source = https://raw.githubusercontent.com/cachyos/kernel-patches/master/6.13/misc/dkms-clang.patch
 	source = https://raw.githubusercontent.com/cachyos/kernel-patches/master/6.13/sched/0001-bore-cachy.patch
 	b2sums = e82921a5852d76802004fa3764f60a916b5a2382d81ec593b63421bdfd09a2222c8afe91905abcbb1d9a4bbb270808cb247ca7f63f1db70abba39c7507133834
-	b2sums = 62156108dc2cf8b2421ca4a90d1281267ba6867b7f8ed11e346a44a88bb699667af405fb4d12e4f72a8815dfb8fbf9c32120270d0455e21ca262cffe982829e9
+	b2sums = b253a968c5a0e28154861b5abe420456d3b5d7d311beb1e7a2a213396600c6be64b8f420d613685d857dfaf52fd9c87bf241320c9f60bf87c7fd59a71acc156e
 	b2sums = 390c7b80608e9017f752b18660cc18ad1ec69f0aab41a2edfcfc26621dcccf5c7051c9d233d9bdf1df63d5f1589549ee0ba3a30e43148509d27dafa9102c19ab
 	b2sums = 1e4cf21d220271d0d63ea23ae13f3172a286eeb858c00d12900bde1691dcf7a0825560f991d97d40f23107aabdada02127b7deb6fead0c1ade0d73ba684e883a
 	b2sums = c7294a689f70b2a44b0c4e9f00c61dbd59dd7063ecbe18655c4e7f12e21ed7c5bb4f5169f5aa8623b1c59de7b2667facb024913ecb9f4c650dabce4e8a7e5452

diff --git a/linux-cachyos-rc/PKGBUILD b/linux-cachyos-rc/PKGBUILD
@@ -422,8 +422,8 @@ prepare() {
         [ -z "$_preempt" ] && _die "The value is empty. Choose the correct one again."
 
         case "$_preempt" in
-            full) scripts/config -e PREEMPT_DYNAMIC -e PREEMPT -d PREEMPT_VOLUNTARY -d PREEMPT_LAZY -d PREEMPT_NONE;;
-            lazy) scripts/config -e PREEMPT_DYNAMIC -d PREEMPT -d PREEMPT_VOLUNTARY -e PREEMPT_LAZY -d PREEMPT_NONE;;
+            full) scripts/config -d PREEMPT_DYNAMIC -e PREEMPT -d PREEMPT_VOLUNTARY -d PREEMPT_LAZY -d PREEMPT_NONE;;
+            lazy) scripts/config -d PREEMPT_DYNAMIC -d PREEMPT -d PREEMPT_VOLUNTARY -e PREEMPT_LAZY -d PREEMPT_NONE;;
             voluntary) scripts/config -d PREEMPT_DYNAMIC -e PREEMPT_VOLUNTARY_BUILD -d PREEMPT -e PREEMPT_VOLUNTARY -d PREEMPT_LAZY -d PREEMPT_NONE;;
             none) scripts/config -d PREEMPT_DYNAMIC -e PREEMPT_NONE_BUILD -d PREEMPT -d PREEMPT_VOLUNTARY -d PREEMPT_LAZY -e PREEMPT_NONE;;
             *) _die "The value '$_preempt' is invalid. Choose the correct one again.";;
@@ -832,7 +832,7 @@ for _p in "${pkgname[@]}"; do
 done
 
 b2sums=('e82921a5852d76802004fa3764f60a916b5a2382d81ec593b63421bdfd09a2222c8afe91905abcbb1d9a4bbb270808cb247ca7f63f1db70abba39c7507133834'
-        '62156108dc2cf8b2421ca4a90d1281267ba6867b7f8ed11e346a44a88bb699667af405fb4d12e4f72a8815dfb8fbf9c32120270d0455e21ca262cffe982829e9'
+        'b253a968c5a0e28154861b5abe420456d3b5d7d311beb1e7a2a213396600c6be64b8f420d613685d857dfaf52fd9c87bf241320c9f60bf87c7fd59a71acc156e'
         '390c7b80608e9017f752b18660cc18ad1ec69f0aab41a2edfcfc26621dcccf5c7051c9d233d9bdf1df63d5f1589549ee0ba3a30e43148509d27dafa9102c19ab'
         '1e4cf21d220271d0d63ea23ae13f3172a286eeb858c00d12900bde1691dcf7a0825560f991d97d40f23107aabdada02127b7deb6fead0c1ade0d73ba684e883a'
         'c7294a689f70b2a44b0c4e9f00c61dbd59dd7063ecbe18655c4e7f12e21ed7c5bb4f5169f5aa8623b1c59de7b2667facb024913ecb9f4c650dabce4e8a7e5452'

diff --git a/linux-cachyos-rc/config b/linux-cachyos-rc/config
@@ -140,7 +140,7 @@ CONFIG_PREEMPT=y
 # CONFIG_PREEMPT_RT is not set
 CONFIG_PREEMPT_COUNT=y
 CONFIG_PREEMPTION=y
-CONFIG_PREEMPT_DYNAMIC=y
+# CONFIG_PREEMPT_DYNAMIC is not set
 CONFIG_SCHED_CORE=y
 CONFIG_SCHED_CLASS_EXT=y