pbs-tools/src/lib.rs

   1 pub mod cert;
   2 pub mod crypt_config;
   3 pub mod format;
   4 pub mod json;
   5 pub mod lru_cache;
   6 pub mod nom;
   7 pub mod sha;
   8
   9 pub mod async_lru_cache;
  10
  11 /// Set MMAP_THRESHOLD to a fixed value (128 KiB)
  12 ///
  13 /// This avoids the "dynamic" mmap-treshold logic from glibc's malloc, which seems misguided and
  14 /// effectively avoids using mmap for all allocations smaller than 32 MiB. Which, in combination
  15 /// with the allocation pattern from our/tokio's complex async machinery, resulted in very large
  16 /// RSS sizes due to defragmentation and long-living (smaller) allocation on top of the heap
  17 /// avoiding that the (big) now free'd allocations below couldn't get given back to the OS. This is
  18 /// not an issue with mmap'd memory chunks, those can be given back at any time.
  19 ///
  20 /// Lowering effective MMAP threshold to 128 KiB allows freeing up memory to the OS better and with
  21 /// lower latency, which reduces the peak *and* average RSS size by an order of magnitude when
  22 /// running backup jobs. We measured a reduction by a factor of 10-20 in experiments and see much
  23 /// less erratic behavior in the overall's runtime RSS size.
  24 pub fn setup_libc_malloc_opts() {
  25     unsafe {
  26         libc::mallopt(libc::M_MMAP_THRESHOLD, 4096 * 32);
  27     }
  28 }