Use top-down allocation for pgalloc.

This change has multiple small components.

First, the chunk size is bumped to 1GB in order to avoid creating excessive
VMAs in the Sentry, which can lead to VMA exhaustion (and hitting limits).

Second, gap-tracking is added to the usage set in order to efficiently scan
for available regions.

Third, reclaim is moved to a simple segment set. This is done to allow the
order of reclaim to align with the Allocate order (which becomes much more
complex when trying to track a "max page" as opposed to "min page", so we
just track explicit segments instead, which should make reclaim scanning
faster anyways).

Finally, the findAvailable function attempts to scan from the top-down, in
order to maximize opportunities for VMA merging in applications (hopefully
preventing the same VMA exhaustion that can affect the Sentry).

PiperOrigin-RevId: 315009249

1 files changed, 3 insertions, 1 deletions

diff --git a/test/e2e/integration_test.go b/test/e2e/integration_test.go
index 9cbb2ed5b..91c956e10 100644
--- a/test/e2e/integration_test.go
+++ b/test/e2e/integration_test.go
@@ -239,7 +239,9 @@ func TestMemLimit(t *testing.T) {
 	d := dockerutil.MakeDocker(t)
 	defer d.CleanUp()
 
-	allocMemory := 500 * 1024
+	// N.B. Because the size of the memory file may grow in large chunks,
+	// there is a minimum threshold of 1GB for the MemTotal figure.
+	allocMemory := 1024 * 1024
 	out, err := d.Run(dockerutil.RunOpts{
 		Image:  "basic/alpine",
 		Memory: allocMemory, // In kB.