Use smaller zlib objects when under memory pressure

We add a compression level argument to tor_zlib_new, and use it to
determine how much memory to allocate for the zlib object.  We use the
existing level by default, but shift to smaller levels for small
requests when we have been over 3/4 of our memory usage in the past
half-hour.

Closes ticket 11791.

diff --git a/changes/bug11791 b/changes/bug11791
new file mode 100644 (file)
index 0000000..51a9327
--- /dev/null
+++ b/changes/bug11791
@@ -0,0 +1,4 @@
+  o Minor features (directory, memory usage):
+    - When we have recently been under memory pressure (over 3/4 of
+      MaxMemInQueues is allocated), then allocate smaller zlib objects for
+      small requests. Closes ticket 11791.

diff --git a/src/common/torgzip.c b/src/common/torgzip.c
index 4480e4b7474a885bd27d25526e27b47f41d0c1aa..05a450e3fbaaf0aa456adc0a2eebf4ad82e2f7ee 100644 (file)
--- a/src/common/torgzip.c
+++ b/src/common/torgzip.c
@@ -92,10 +92,27 @@ tor_zlib_get_header_version_str(void)
 
 /** Return the 'bits' value to tell zlib to use <b>method</b>.*/
 static INLINE int
-method_bits(compress_method_t method)
+method_bits(compress_method_t method, zlib_compression_level_t level)
 {
   /* Bits+16 means "use gzip" in zlib >= 1.2 */
-  return method == GZIP_METHOD ? 15+16 : 15;
+  const int flag = method == GZIP_METHOD ? 16 : 0;
+  switch (level) {
+    default:
+    case HIGH_COMPRESSION: return flag + 15;
+    case MEDIUM_COMPRESSION: return flag + 13;
+    case LOW_COMPRESSION: return flag + 11;
+  }
+}
+
+static INLINE int
+get_memlevel(zlib_compression_level_t level)
+{
+  switch (level) {
+    default:
+    case HIGH_COMPRESSION: return 8;
+    case MEDIUM_COMPRESSION: return 7;
+    case LOW_COMPRESSION: return 6;
+  }
 }
 
 /** @{ */
@@ -162,8 +179,9 @@ tor_gzip_compress(char **out, size_t *out_len,
   stream->avail_in = (unsigned int)in_len;
 
   if (deflateInit2(stream, Z_BEST_COMPRESSION, Z_DEFLATED,
-                   method_bits(method),
-                   8, Z_DEFAULT_STRATEGY) != Z_OK) {
+                   method_bits(method, HIGH_COMPRESSION),
+                   get_memlevel(HIGH_COMPRESSION),
+                   Z_DEFAULT_STRATEGY) != Z_OK) {
     log_warn(LD_GENERAL, "Error from deflateInit2: %s",
              stream->msg?stream->msg:"<no message>");
     goto err;
@@ -289,7 +307,7 @@ tor_gzip_uncompress(char **out, size_t *out_len,
   stream->avail_in = (unsigned int)in_len;
 
   if (inflateInit2(stream,
-                   method_bits(method)) != Z_OK) {
+                   method_bits(method, HIGH_COMPRESSION)) != Z_OK) {
     log_warn(LD_GENERAL, "Error from inflateInit2: %s",
              stream->msg?stream->msg:"<no message>");
     goto err;
@@ -315,7 +333,8 @@ tor_gzip_uncompress(char **out, size_t *out_len,
           log_warn(LD_BUG, "Error freeing gzip structures");
           goto err;
         }
-        if (inflateInit2(stream, method_bits(method)) != Z_OK) {
+        if (inflateInit2(stream,
+                         method_bits(method,HIGH_COMPRESSION)) != Z_OK) {
           log_warn(LD_GENERAL, "Error from second inflateInit2: %s",
                    stream->msg?stream->msg:"<no message>");
           goto err;
@@ -426,10 +445,11 @@ struct tor_zlib_state_t {
  * <b>compress</b>, it's for compression; otherwise it's for
  * decompression. */
 tor_zlib_state_t *
-tor_zlib_new(int compress, compress_method_t method)
+tor_zlib_new(int compress, compress_method_t method,
+             zlib_compression_level_t compression_level)
 {
   tor_zlib_state_t *out;
-  int bits;
+  int bits, memlevel;
 
   if (method == GZIP_METHOD && !is_gzip_supported()) {
     /* Old zlib version don't support gzip in inflateInit2 */
@@ -437,21 +457,29 @@ tor_zlib_new(int compress, compress_method_t method)
     return NULL;
  }
 
+ if (! compress) {
+   /* use this setting for decompression, since we might have the
+    * max number of window bits */
+   compression_level = HIGH_COMPRESSION;
+ }
+
  out = tor_malloc_zero(sizeof(tor_zlib_state_t));
  out->stream.zalloc = Z_NULL;
  out->stream.zfree = Z_NULL;
  out->stream.opaque = NULL;
  out->compress = compress;
- bits = method_bits(method);
+ bits = method_bits(method, compression_level);
+ memlevel = get_memlevel(compression_level);
  if (compress) {
    if (deflateInit2(&out->stream, Z_BEST_COMPRESSION, Z_DEFLATED,
-                    bits, 8, Z_DEFAULT_STRATEGY) != Z_OK)
+                    bits, memlevel,
+                    Z_DEFAULT_STRATEGY) != Z_OK)
      goto err;
  } else {
    if (inflateInit2(&out->stream, bits) != Z_OK)
      goto err;
  }
- out->allocation = tor_zlib_state_size_precalc(!compress, bits, 8);
+ out->allocation = tor_zlib_state_size_precalc(!compress, bits, memlevel);
 
  total_zlib_allocation += out->allocation;
 

diff --git a/src/common/torgzip.h b/src/common/torgzip.h
index 1378d55b7618e5eea3a759944ea0f3aa9570c0a7..eaba2712bb0a90708a63c422ef55dcd4142c614b 100644 (file)
--- a/src/common/torgzip.h
+++ b/src/common/torgzip.h
@@ -19,6 +19,15 @@ typedef enum {
   NO_METHOD=0, GZIP_METHOD=1, ZLIB_METHOD=2, UNKNOWN_METHOD=3
 } compress_method_t;
 
+/**
+ * Enumeration to define tradeoffs between memory usage and compression level.
+ * HIGH_COMPRESSION saves the most bandwidth; LOW_COMPRESSION saves the most
+ * memory.
+ **/
+typedef enum {
+  HIGH_COMPRESSION, MEDIUM_COMPRESSION, LOW_COMPRESSION
+} zlib_compression_level_t;
+
 int
 tor_gzip_compress(char **out, size_t *out_len,
                   const char *in, size_t in_len,
@@ -47,7 +56,8 @@ typedef enum {
 } tor_zlib_output_t;
 /** Internal state for an incremental zlib compression/decompression. */
 typedef struct tor_zlib_state_t tor_zlib_state_t;
-tor_zlib_state_t *tor_zlib_new(int compress, compress_method_t method);
+tor_zlib_state_t *tor_zlib_new(int compress, compress_method_t method,
+                               zlib_compression_level_t level);
 
 tor_zlib_output_t tor_zlib_process(tor_zlib_state_t *state,
                                    char **out, size_t *out_len,

diff --git a/src/or/config.c b/src/or/config.c
index 4b8c6834e9972f3131dd10e93080bf514ff908fc..d33829a03ff15a89842d34057a0977b88e778390 100644 (file)
--- a/src/or/config.c
+++ b/src/or/config.c
@@ -2828,6 +2828,7 @@ options_validate(or_options_t *old_options, or_options_t *options,
   options->MaxMemInQueues =
     compute_real_max_mem_in_queues(options->MaxMemInQueues_raw,
                                    server_mode(options));
+  options->MaxMemInQueues_low_threshold = (options->MaxMemInQueues / 4) * 3;
 
   options->AllowInvalid_ = 0;
 

diff --git a/src/or/directory.c b/src/or/directory.c
index e1f5964e1e891208c9b1e2b9cc57c177bc2f396d..0ab3e6ae23f54e1dca33b7e47a3f75d6f0c84151 100644 (file)
--- a/src/or/directory.c
+++ b/src/or/directory.c
@@ -20,6 +20,7 @@
 #include "networkstatus.h"
 #include "nodelist.h"
 #include "policies.h"
+#include "relay.h"
 #include "rendclient.h"
 #include "rendcommon.h"
 #include "rephist.h"
@@ -2521,6 +2522,24 @@ client_likes_consensus(networkstatus_t *v, const char *want_url)
   return (have >= need_at_least);
 }
 
+/** Return the compression level we should use for sending a compressed
+ * response of size <b>n_bytes</b>. */
+static zlib_compression_level_t
+choose_compression_level(ssize_t n_bytes)
+{
+  if (! have_been_under_memory_pressure()) {
+    return HIGH_COMPRESSION; /* we have plenty of RAM. */
+  } else if (n_bytes < 0) {
+    return HIGH_COMPRESSION; /* unknown; might be big. */
+  } else if (n_bytes < 1024) {
+    return LOW_COMPRESSION;
+  } else if (n_bytes < 2048) {
+    return MEDIUM_COMPRESSION;
+  } else {
+    return HIGH_COMPRESSION;
+  }
+}
+
 /** Helper function: called when a dirserver gets a complete HTTP GET
  * request.  Look for a request for a directory or for a rendezvous
  * service descriptor.  On finding one, write a response into
@@ -2703,7 +2722,7 @@ directory_handle_command_get(dir_connection_t *conn, const char *headers,
                                smartlist_len(dir_fps) == 1 ? lifetime : 0);
     conn->fingerprint_stack = dir_fps;
     if (! compressed)
-      conn->zlib_state = tor_zlib_new(0, ZLIB_METHOD);
+      conn->zlib_state = tor_zlib_new(0, ZLIB_METHOD, HIGH_COMPRESSION);
 
     /* Prime the connection with some data. */
     conn->dir_spool_src = DIR_SPOOL_NETWORKSTATUS;
@@ -2791,7 +2810,8 @@ directory_handle_command_get(dir_connection_t *conn, const char *headers,
 
     if (smartlist_len(items)) {
       if (compressed) {
-        conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD);
+        conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD,
+                                    choose_compression_level(estimated_len));
         SMARTLIST_FOREACH(items, const char *, c,
                  connection_write_to_buf_zlib(c, strlen(c), conn, 0));
         connection_write_to_buf_zlib("", 0, conn, 1);
@@ -2840,7 +2860,8 @@ directory_handle_command_get(dir_connection_t *conn, const char *headers,
     conn->fingerprint_stack = fps;
 
     if (compressed)
-      conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD);
+      conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD,
+                                      choose_compression_level(dlen));
 
     connection_dirserv_flushed_some(conn);
     goto done;
@@ -2908,7 +2929,8 @@ directory_handle_command_get(dir_connection_t *conn, const char *headers,
       }
       write_http_response_header(conn, -1, compressed, cache_lifetime);
       if (compressed)
-        conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD);
+        conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD,
+                                        choose_compression_level(dlen));
       /* Prime the connection with some data. */
       connection_dirserv_flushed_some(conn);
     }
@@ -2983,7 +3005,8 @@ directory_handle_command_get(dir_connection_t *conn, const char *headers,
 
     write_http_response_header(conn, compressed?-1:len, compressed, 60*60);
     if (compressed) {
-      conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD);
+      conn->zlib_state = tor_zlib_new(1, ZLIB_METHOD,
+                                      choose_compression_level(len));
       SMARTLIST_FOREACH(certs, authority_cert_t *, c,
             connection_write_to_buf_zlib(c->cache_info.signed_descriptor_body,
                                          c->cache_info.signed_descriptor_len,

diff --git a/src/or/dirserv.c b/src/or/dirserv.c
index d31bb72361173903bd99d4ceb14addc6c5fb07bd..635d691afbc7c6e97cca070570f6e6b8d2d8686d 100644 (file)
--- a/src/or/dirserv.c
+++ b/src/or/dirserv.c
@@ -3182,7 +3182,7 @@ connection_dirserv_add_networkstatus_bytes_to_outbuf(dir_connection_t *conn)
         if (uncompressing && ! conn->zlib_state &&
             conn->fingerprint_stack &&
             smartlist_len(conn->fingerprint_stack)) {
-          conn->zlib_state = tor_zlib_new(0, ZLIB_METHOD);
+          conn->zlib_state = tor_zlib_new(0, ZLIB_METHOD, HIGH_COMPRESSION);
         }
       }
       if (r) return r;

diff --git a/src/or/or.h b/src/or/or.h
index 5ebe7bfac37e67a93452135044ed9c293f9e31b2..a9371f576842d4f91e3bb09194a907760e1dbef4 100644 (file)
--- a/src/or/or.h
+++ b/src/or/or.h
@@ -3514,6 +3514,8 @@ typedef struct {
   uint64_t MaxMemInQueues_raw;
   uint64_t MaxMemInQueues;/**< If we have more memory than this allocated
                             * for queues and buffers, run the OOM handler */
+  /** Above this value, consider ourselves low on RAM. */
+  uint64_t MaxMemInQueues_low_threshold;
 
   /** @name port booleans
    *

diff --git a/src/or/relay.c b/src/or/relay.c
index 05c7b3c955c9eb7fee35d29824f10f8da61566b9..a899fc09cb32b82a57fc6a527da3a7249242fe52 100644 (file)
--- a/src/or/relay.c
+++ b/src/or/relay.c
@@ -2432,6 +2432,12 @@ cell_queues_get_total_allocation(void)
   return total_cells_allocated * packed_cell_mem_cost();
 }
 
+/** How long after we've been low on memory should we try to conserve it? */
+#define MEMORY_PRESSURE_INTERVAL (30*60)
+
+/** The time at which we were last low on memory. */
+static time_t last_time_under_memory_pressure = 0;
+
 /** Check whether we've got too much space used for cells.  If so,
  * call the OOM handler and return 1.  Otherwise, return 0. */
 STATIC int
@@ -2440,13 +2446,25 @@ cell_queues_check_size(void)
   size_t alloc = cell_queues_get_total_allocation();
   alloc += buf_get_total_allocation();
   alloc += tor_zlib_get_total_allocation();
-  if (alloc >= get_options()->MaxMemInQueues) {
-    circuits_handle_oom(alloc);
-    return 1;
+  if (alloc >= get_options()->MaxMemInQueues_low_threshold) {
+    last_time_under_memory_pressure = approx_time();
+    if (alloc >= get_options()->MaxMemInQueues) {
+      circuits_handle_oom(alloc);
+      return 1;
+    }
   }
   return 0;
 }
 
+/** Return true if we've been under memory pressure in the last
+ * MEMORY_PRESSURE_INTERVAL seconds. */
+int
+have_been_under_memory_pressure(void)
+{
+  return last_time_under_memory_pressure + MEMORY_PRESSURE_INTERVAL
+    < approx_time();
+}
+
 /**
  * Update the number of cells available on the circuit's n_chan or p_chan's
  * circuit mux.

diff --git a/src/or/relay.h b/src/or/relay.h
index 73c399154de56d48fa09adcf151ce367d319b185..3bc668374fa206b39a0952cd5a7ba93e477be155 100644 (file)
--- a/src/or/relay.h
+++ b/src/or/relay.h
@@ -50,6 +50,8 @@ void clean_cell_pool(void);
 void dump_cell_pool_usage(int severity);
 size_t packed_cell_mem_cost(void);
 
+int have_been_under_memory_pressure(void);
+
 /* For channeltls.c */
 void packed_cell_free(packed_cell_t *cell);
 

diff --git a/src/test/test_buffers.c b/src/test/test_buffers.c
index cb29ab0a9ee138356119c60c79c5f93ca04e7b3e..e24aa8ec8604e0b3292a9a2c8ec8c76017803a87 100644 (file)
--- a/src/test/test_buffers.c
+++ b/src/test/test_buffers.c
@@ -611,7 +611,7 @@ test_buffers_zlib_impl(int finalize_with_nil)
   int done;
 
   buf = buf_new_with_capacity(128); /* will round up */
-  zlib_state = tor_zlib_new(1, ZLIB_METHOD);
+  zlib_state = tor_zlib_new(1, ZLIB_METHOD, HIGH_COMPRESSION);
 
   msg = tor_malloc(512);
   crypto_rand(msg, 512);
@@ -688,7 +688,7 @@ test_buffers_zlib_fin_at_chunk_end(void *arg)
   tt_uint_op(buf->head->datalen, OP_EQ, headerjunk);
   tt_uint_op(buf_datalen(buf), OP_EQ, headerjunk);
   /* Write an empty string, with finalization on. */
-  zlib_state = tor_zlib_new(1, ZLIB_METHOD);
+  zlib_state = tor_zlib_new(1, ZLIB_METHOD, HIGH_COMPRESSION);
   tt_int_op(write_to_buf_zlib(buf, zlib_state, "", 0, 1), OP_EQ, 0);
 
   in_len = buf_datalen(buf);

diff --git a/src/test/test_util.c b/src/test/test_util.c
index b952bb2596ab1b5dec13c7c413b400dabb862ca6..3fbe465ecee63820ffde39adeb12704d1f8d9fab 100644 (file)
--- a/src/test/test_util.c
+++ b/src/test/test_util.c
@@ -1820,7 +1820,7 @@ test_util_gzip(void *arg)
   tor_free(buf1);
   tor_free(buf2);
   tor_free(buf3);
-  state = tor_zlib_new(1, ZLIB_METHOD);
+  state = tor_zlib_new(1, ZLIB_METHOD, HIGH_COMPRESSION);
   tt_assert(state);
   cp1 = buf1 = tor_malloc(1024);
   len1 = 1024;