pub mod ticket;
pub mod async_lru_cache;
+
+/// Set MMAP_THRESHOLD to a fixed value (128 KiB)
+///
+/// This avoids the "dynamic" mmap-treshold logic from glibc's malloc, which seems misguided and
+/// effectively avoids using mmap for all allocations smaller than 32 MiB. Which, in combination
+/// with the allocation pattern from our/tokio's complex async machinery, resulted in very large
+/// RSS sizes due to defragmentation and long-living (smaller) allocation on top of the heap
+/// avoiding that the (big) now free'd allocations below couldn't get given back to the OS. This is
+/// not an issue with mmap'd memeory chunks, those can be given back at any time.
+///
+/// Lowering effective MMAP treshold to 128 KiB allows freeing up memory to the OS better and with
+/// lower latency, which reduces the peak *and* average RSS size by an order of magnitude when
+/// running backup jobs. We measured a reduction by a factor of 10-20 in experiments and see much
+/// less erratic behavior in the overall's runtime RSS size.
+pub fn setup_libc_malloc_opts() {
+ unsafe {
+ libc::mallopt(libc::M_MMAP_THRESHOLD, 4096*32);
+ }
+}