tor

commit b2536c97f941ad2e4e068c43f8ce18469c63585c
parent 2243fc3ad1bb33ca5f4a37952bb474d8314d5325
Author: Nick Mathewson <nickm@torproject.org>
Date:   Thu, 21 Jan 2021 13:40:46 -0500

Merge branch 'maint-0.4.5'

Diffstat:
A
changes/bug24857
 | 
6
++++++
M
src/feature/dircache/consdiffmgr.c
 | 
12
+++++++++++-

2 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/changes/bug24857 b/changes/bug24857
@@ -0,0 +1,6 @@
+  o Minor bugfixes (directory cache, performance, windows):
+    - Limit the number of items in the consensus diff cache to 64 on Windows.
+      We hope this will resolve an issue where Windows relay operators reported
+      Tor using 100% CPU while we investigate better solutions. Fixes bug 24857;
+      bugfix on 0.3.1.1-alpha.
+
diff --git a/src/feature/dircache/consdiffmgr.c b/src/feature/dircache/consdiffmgr.c
@@ -177,6 +177,16 @@ typedef struct cdm_diff_t {
 /** Hashtable mapping flavor and source consensus digest to status. */
 static HT_HEAD(cdm_diff_ht, cdm_diff_t) cdm_diff_ht = HT_INITIALIZER();
 
+#ifdef _WIN32
+   // XXX(ahf): For tor#24857, a contributor suggested that on Windows, the CPU
+   // begins to spike at 100% once the number of files handled by the consensus
+   // diff manager becomes larger than 64. To see if the issue goes away, we
+   // hardcode this value to 64 now while we investigate a better solution.
+#  define CACHE_MAX_NUM 64
+#else
+#  define CACHE_MAX_NUM 128
+#endif
+
 /**
  * Configuration for this module
  */
@@ -184,7 +194,7 @@ static consdiff_cfg_t consdiff_cfg = {
   // XXXX I'd like to make this number bigger, but it interferes with the
   // XXXX seccomp2 syscall filter, which tops out at BPF_MAXINS (4096)
   // XXXX rules.
-  /* .cache_max_num = */ 128
+  /* .cache_max_num = */ CACHE_MAX_NUM
 };
 
 static int consdiffmgr_ensure_space_for_files(int n);