pageserver,safekeeper: disable heap profiling (#10268)

## Problem

Since enabling continuous profiling in staging, we've seen frequent seg
faults. This is suspected to be because jemalloc and pprof-rs take a
stack trace at the same time, and the handlers aren't signal safe.
jemalloc does this probabilistically on every allocation, regardless of
whether someone is taking a heap profile, which means that any CPU
profile has a chance to cause a seg fault.

Touches #10225.

## Summary of changes

For now, just disable heap profiles -- CPU profiles are more important,
and we need to be able to take them without risking a crash.

pageserver/src/bin/pageserver.rs

@@ -53,10 +53,12 @@ project_build_tag!(BUILD_TAG);
 #[global_allocator]
 static GLOBAL: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;
 
-/// Configure jemalloc to sample allocations for profiles every 1 MB (1 << 20).
-#[allow(non_upper_case_globals)]
-#[export_name = "malloc_conf"]
-pub static malloc_conf: &[u8] = b"prof:true,prof_active:true,lg_prof_sample:20\0";
+// Configure jemalloc to sample allocations for profiles every 1 MB (1 << 20).
+// TODO: disabled because concurrent CPU profiles cause seg faults. See:
+// https://github.com/neondatabase/neon/issues/10225.
+//#[allow(non_upper_case_globals)]
+//#[export_name = "malloc_conf"]
+//pub static malloc_conf: &[u8] = b"prof:true,prof_active:true,lg_prof_sample:20\0";
 
 const PID_FILE_NAME: &str = "pageserver.pid";
 

safekeeper/src/bin/safekeeper.rs

@@ -51,10 +51,12 @@ use utils::{
 #[global_allocator]
 static GLOBAL: tikv_jemallocator::Jemalloc = tikv_jemallocator::Jemalloc;
 
-/// Configure jemalloc to sample allocations for profiles every 1 MB (1 << 20).
-#[allow(non_upper_case_globals)]
-#[export_name = "malloc_conf"]
-pub static malloc_conf: &[u8] = b"prof:true,prof_active:true,lg_prof_sample:20\0";
+// Configure jemalloc to sample allocations for profiles every 1 MB (1 << 20).
+// TODO: disabled because concurrent CPU profiles cause seg faults. See:
+// https://github.com/neondatabase/neon/issues/10225.
+//#[allow(non_upper_case_globals)]
+//#[export_name = "malloc_conf"]
+//pub static malloc_conf: &[u8] = b"prof:true,prof_active:true,lg_prof_sample:20\0";
 
 const PID_FILE_NAME: &str = "safekeeper.pid";
 const ID_FILE_NAME: &str = "safekeeper.id";