[tor-commits] [tor/maint-0.4.5] relay: Reduce streaming compression ratio from HIGH to LOW
ahf at torproject.org
ahf at torproject.org
Wed Aug 11 13:13:05 UTC 2021
commit 399518da022ea94bd0644082e29012a51aec5697
Author: David Goulet <dgoulet at torproject.org>
Date: Thu Feb 18 12:49:33 2021 -0500
relay: Reduce streaming compression ratio from HIGH to LOW
Fixes #40301
Signed-off-by: David Goulet <dgoulet at torproject.org>
---
changes/ticket40301 | 4 ++++
src/feature/dircache/dircache.c | 35 +++++++++++++++++++----------------
src/feature/dircache/dircache.h | 2 +-
src/lib/compress/compress_zstd.c | 4 ++--
src/test/test_dir.c | 26 --------------------------
5 files changed, 26 insertions(+), 45 deletions(-)
diff --git a/changes/ticket40301 b/changes/ticket40301
new file mode 100644
index 0000000000..c1fd821e3f
--- /dev/null
+++ b/changes/ticket40301
@@ -0,0 +1,4 @@
+ o Minor bugfixes (relay):
+ - Reduce the compression level for data streaming from HIGH to LOW. Fixes
+ bug 40301; bugfix on 0.3.5.1-alpha.
+
diff --git a/src/feature/dircache/dircache.c b/src/feature/dircache/dircache.c
index e8cb284165..2f8a281cd1 100644
--- a/src/feature/dircache/dircache.c
+++ b/src/feature/dircache/dircache.c
@@ -294,19 +294,22 @@ client_likes_consensus(const struct consensus_cache_entry_t *ent,
/** Return the compression level we should use for sending a compressed
* response of size <b>n_bytes</b>. */
STATIC compression_level_t
-choose_compression_level(ssize_t n_bytes)
+choose_compression_level(void)
{
- 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;
- }
+ /* This is the compression level choice for a stream.
+ *
+ * We always return LOW because this compression is done in the main thread
+ * thus we save CPU time as much as possible, and it is also done more than
+ * background compression for document we serve pre-compressed.
+ *
+ * GZip highest compression level (9) gives us a ratio of 49.72%
+ * Zstd lowest compression level (1) gives us a ratio of 47.38%
+ *
+ * Thus, as the network moves more and more to use Zstd when requesting
+ * directory documents that are not pre-cached, even at the
+ * lowest level, we still gain over GZip and thus help with load and CPU
+ * time on the network. */
+ return LOW_COMPRESSION;
}
/** Information passed to handle a GET request. */
@@ -1044,7 +1047,7 @@ handle_get_status_vote(dir_connection_t *conn, const get_handler_args_t *args)
if (smartlist_len(items)) {
if (compress_method != NO_METHOD) {
conn->compress_state = tor_compress_new(1, compress_method,
- choose_compression_level(estimated_len));
+ choose_compression_level());
SMARTLIST_FOREACH(items, const char *, c,
connection_buf_add_compress(c, strlen(c), conn, 0));
connection_buf_add_compress("", 0, conn, 1);
@@ -1109,7 +1112,7 @@ handle_get_microdesc(dir_connection_t *conn, const get_handler_args_t *args)
if (compress_method != NO_METHOD)
conn->compress_state = tor_compress_new(1, compress_method,
- choose_compression_level(size_guess));
+ choose_compression_level());
const int initial_flush_result = connection_dirserv_flushed_some(conn);
tor_assert_nonfatal(initial_flush_result == 0);
@@ -1204,7 +1207,7 @@ handle_get_descriptor(dir_connection_t *conn, const get_handler_args_t *args)
write_http_response_header(conn, -1, compress_method, cache_lifetime);
if (compress_method != NO_METHOD)
conn->compress_state = tor_compress_new(1, compress_method,
- choose_compression_level(size_guess));
+ choose_compression_level());
clear_spool = 0;
/* Prime the connection with some data. */
int initial_flush_result = connection_dirserv_flushed_some(conn);
@@ -1301,7 +1304,7 @@ handle_get_keys(dir_connection_t *conn, const get_handler_args_t *args)
60*60);
if (compress_method != NO_METHOD) {
conn->compress_state = tor_compress_new(1, compress_method,
- choose_compression_level(len));
+ choose_compression_level());
SMARTLIST_FOREACH(certs, authority_cert_t *, c,
connection_buf_add_compress(
c->cache_info.signed_descriptor_body,
diff --git a/src/feature/dircache/dircache.h b/src/feature/dircache/dircache.h
index 236ea649ef..44e40d108c 100644
--- a/src/feature/dircache/dircache.h
+++ b/src/feature/dircache/dircache.h
@@ -26,7 +26,7 @@ MOCK_DECL(STATIC int, directory_handle_command_post,(dir_connection_t *conn,
STATIC int handle_post_hs_descriptor(const char *url, const char *body);
enum compression_level_t;
-STATIC enum compression_level_t choose_compression_level(ssize_t n_bytes);
+STATIC enum compression_level_t choose_compression_level(void);
struct get_handler_args_t;
STATIC int handle_get_hs_descriptor_v3(dir_connection_t *conn,
diff --git a/src/lib/compress/compress_zstd.c b/src/lib/compress/compress_zstd.c
index 45d0d4d602..f0bb22b517 100644
--- a/src/lib/compress/compress_zstd.c
+++ b/src/lib/compress/compress_zstd.c
@@ -49,8 +49,8 @@ memory_level(compression_level_t level)
default:
case BEST_COMPRESSION:
case HIGH_COMPRESSION: return 9;
- case MEDIUM_COMPRESSION: return 8;
- case LOW_COMPRESSION: return 7;
+ case MEDIUM_COMPRESSION: return 3;
+ case LOW_COMPRESSION: return 1;
}
}
#endif /* defined(HAVE_ZSTD) */
diff --git a/src/test/test_dir.c b/src/test/test_dir.c
index 0e44c47f3f..4c074d0c3e 100644
--- a/src/test/test_dir.c
+++ b/src/test/test_dir.c
@@ -4859,31 +4859,6 @@ NS(directory_initiate_request)(directory_request_t *req)
CALLED(directory_initiate_request)++;
}
-static void
-test_dir_choose_compression_level(void* data)
-{
- (void)data;
-
- /* It starts under_memory_pressure */
- tt_int_op(have_been_under_memory_pressure(), OP_EQ, 1);
-
- tt_assert(HIGH_COMPRESSION == choose_compression_level(-1));
- tt_assert(LOW_COMPRESSION == choose_compression_level(1024-1));
- tt_assert(MEDIUM_COMPRESSION == choose_compression_level(2048-1));
- tt_assert(HIGH_COMPRESSION == choose_compression_level(2048));
-
- /* Reset under_memory_pressure timer */
- cell_queues_check_size();
- tt_int_op(have_been_under_memory_pressure(), OP_EQ, 0);
-
- tt_assert(HIGH_COMPRESSION == choose_compression_level(-1));
- tt_assert(HIGH_COMPRESSION == choose_compression_level(1024-1));
- tt_assert(HIGH_COMPRESSION == choose_compression_level(2048-1));
- tt_assert(HIGH_COMPRESSION == choose_compression_level(2048));
-
- done: ;
-}
-
/*
* Mock check_private_dir(), and always succeed - no need to actually
* look at or create anything on the filesystem.
@@ -6397,7 +6372,6 @@ struct testcase_t dir_tests[] = {
DIR(should_not_init_request_to_ourselves, TT_FORK),
DIR(should_not_init_request_to_dir_auths_without_v3_info, 0),
DIR(should_init_request_to_dir_auths, 0),
- DIR(choose_compression_level, 0),
DIR(dump_unparseable_descriptors, 0),
DIR(populate_dump_desc_fifo, 0),
DIR(populate_dump_desc_fifo_2, 0),
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