Tentative re-write of the linker memory usage workaround

2 files changed, 49 insertions, 26 deletions

diff --git a/PKGBUILD b/PKGBUILD
index a2402b2b2efd..bbbe74d85640 100755
--- a/PKGBUILD
+++ b/PKGBUILD
@@ -31,7 +31,7 @@ install=alchemy.install
 source=("${pkgname}"::'git+https://git.alchemyviewer.org/alchemy/alchemy-next.git#branch='"${AL_BRANCH_OVERRIDE:-main}"
 'compile.bash')
 sha256sums=('SKIP'
-            '7c841143956b312b2abb47d89151be9522e6fb0391450e311a3f4696aa05f792')
+            'b1804aa12f4ae454db93436b58a5cf2dfc8dfee191959e4209abfa2c6788980f')
 
 pkgver() {
     cd "${pkgname}" || exit 1
diff --git a/compile.bash b/compile.bash
index 9a20852afa30..510983f5482d 100755
--- a/compile.bash
+++ b/compile.bash
@@ -32,32 +32,55 @@ build() {
 	fi
 	ulimit -n 20000
 	build_jobs=$(nproc)
-	if [[ ${build_jobs} -gt 1 ]]; then
-		mempercorekb=$((4 * 1048576))
-		# The viewer requires an average of 4GB of memory per core to link
-		requiredmemorykb=$(($(nproc) * mempercorekb))
-		# Source: Total Used Free
-		free_output="$(free --kilo --total | tail -n+2| tr -s ' ')"
-		totalmemorykb=$(grep Total <<< "$free_output" | cut -d ' ' -f 2)
-		availablememorykb=$(cut -d ' ' -f 7 <<< "$free_output")
-		echo "Total memory:         $totalmemorykb (includes swap)"
-		echo "Available memory:     $availablememorykb"
-		echo "Required memory:      $requiredmemorykb"
-		if [[ ${requiredmemorykb} -gt ${totalmemorykb} ]]; then
+	if [[ -z "$NO_SMART_JOB_COUNT" ]]; then
+		if [[ ${build_jobs} -gt 1 ]]; then
+			jobs=1
+			# The viewer requires an average of 4GB of memory per core to link
+			# Note: Behaviour change compared to the previous versions:
+			# This script will no longer try to allocate build memory into swap
+			# This is bad practice, and swap should be reserved to evict process
+			# memory from physical ram to make place for the current workset.
+			# This script will now try to check if swap is present and sufficent
+			# for the current used memory to be stored in swap before allocating,
+			# and will fallback to conservative allocation if swap is not available
+			gigperlinkprocess=4
+			mempercorekb=$((gigperlinkprocess * 1048576))
+			requiredmemorykb=$(($(nproc) * mempercorekb))
+			free_output="$(free --kilo --total | tail -n+2| tr -s ' ')"
+			physical_output=$(grep "Mem:" <<< "$free_output")
+			#total_output=$(grep Total: <<< "$free_output")
+			usedmemorykbphysical=$(cut -d ' ' -f 3 <<< "$physical_output")
+			totalmemorykbphysical=$(cut -d ' ' -f 2 <<< "$physical_output")
+			swap_output=$(grep Swap: <<< "$free_output")
+			# Determine available swap space
+			availableswapkb=0
+			if [[ -n "$swap_output" ]]; then
+				availableswapkb=$(cut -d ' ' -f 4 <<< "$swap_output")
+			fi
+			availablememorykbphysical=$(cut -d ' ' -f 7 <<< "$free_output")
+			echo "Total memory:         $totalmemorykbphysical (includes swap)"
+			echo "Available memory:     $availablememorykbphysical"
+			echo "Required memory:      $requiredmemorykb"
+			echo "Available physical memory on this system: $((availablememorykbphysical/1024/1024)) GB"
 			echo "Estimated required memory to build with all cores: $((requiredmemorykb/1024/1024)) GB"
-			echo "Available memory on this system: $((availablememorykb/1024/1024)) GB"
-			echo "Warning: Not enough physical memory to build with all cores, adjusting"
-			if [[ ${requiredmemorykb} -gt ${availablememorykb} ]]; then
-				jobs=1
-				echo "Allocating build jobs according to available memory (including swap) (${availablememorykb}/${requiredmemorykb})..."
-				# FIXME: Goes one iteration beyond what it should
-				while [[ $((jobs * mempercorekb)) -lt ${availablememorykb} ]]; do
-					jobs=$((jobs+1))
-					echo -e "${jobs} jobs would consume $(((jobs * mempercorekb)/1024/1024))GB"
-				done
-				# Back off one job count. Not sure why I have to do this but
-				# the loop is doing one extra iteration.
-				jobs=$((jobs-1))
+			if [[ ${requiredmemorykb} -gt ${availablememorykbphysical} ]]; then
+				echo "Warning: Not enough available physical memory to build with all cores"
+				if [[ ${usedmemorykbphysical} -lt ${availableswapkb} ]]; then
+					# use all physical ram as swap will do its job
+					echo "There is enough free swap to store the currently used memory"
+					jobs=$(((totalmemorykbphysical/1024/1024)/gigperlinkprocess))
+				else
+					# Not enough swap to hold ram contents, calculate manually
+					echo "Allocating build jobs according to available physical memory ("$((availablememorykbphysical/1024/1024))"/"$((requiredmemorykb/1024/1024))"GB)..."
+					# FIXME: Goes one iteration beyond what it should
+					while [[ $((jobs * mempercorekb)) -lt ${availablememorykbphysical} ]]; do
+						jobs=$((jobs+1))
+						echo -e "${jobs} jobs would consume $(((jobs * mempercorekb)/1024/1024))GB"
+					done
+					# Back off one job count. Not sure why I have to do this but
+					# the loop is doing one extra iteration.
+					jobs=$((jobs-1))
+				fi
 				build_jobs=${jobs}
 				echo "Computed job count: ${build_jobs}"
 			fi