journal: provide compress_threshold_bytes parameter

Previously the compression threshold was hardcoded to 512, which meant that
smaller values wouldn't be compressed. This left some storage savings on the
table, so instead, we make that number tunable.

1 files changed, 24 insertions, 6 deletions

diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index 5643c0578d..5fc61b16e0 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -51,7 +51,8 @@
 #define DEFAULT_DATA_HASH_TABLE_SIZE (2047ULL*sizeof(HashItem))
 #define DEFAULT_FIELD_HASH_TABLE_SIZE (333ULL*sizeof(HashItem))
 
-#define COMPRESSION_SIZE_THRESHOLD (512ULL)
+#define DEFAULT_COMPRESS_THRESHOLD (512ULL)
+#define MIN_COMPRESS_THRESHOLD (8ULL)
 
 /* This is the minimum journal file size */
 #define JOURNAL_FILE_SIZE_MIN (512ULL*1024ULL)                 /* 512 KiB */
@@ -1552,7 +1553,7 @@ static int journal_file_append_data(
         o->data.hash = htole64(hash);
 
 #if HAVE_XZ || HAVE_LZ4
-        if (JOURNAL_FILE_COMPRESS(f) && size >= COMPRESSION_SIZE_THRESHOLD) {
+        if (JOURNAL_FILE_COMPRESS(f) && size >= f->compress_threshold_bytes) {
                 size_t rsize = 0;
 
                 compression = compress_blob(data, size, o->data.payload, size - 1, &rsize);
@@ -3211,6 +3212,7 @@ int journal_file_open(
                 int flags,
                 mode_t mode,
                 bool compress,
+                uint64_t compress_threshold_bytes,
                 bool seal,
                 JournalMetrics *metrics,
                 MMapCache *mmap_cache,
@@ -3222,6 +3224,7 @@ int journal_file_open(
         JournalFile *f;
         void *h;
         int r;
+        char bytes[FORMAT_BYTES_MAX];
 
         assert(ret);
         assert(fd >= 0 || fname);
@@ -3247,10 +3250,20 @@ int journal_file_open(
 #elif HAVE_XZ
         f->compress_xz = compress;
 #endif
+
+        if (compress_threshold_bytes == (uint64_t) -1)
+                f->compress_threshold_bytes = DEFAULT_COMPRESS_THRESHOLD;
+        else
+                f->compress_threshold_bytes = MAX(MIN_COMPRESS_THRESHOLD, compress_threshold_bytes);
+
 #if HAVE_GCRYPT
         f->seal = seal;
 #endif
 
+        log_debug("Journal effective settings seal=%s compress=%s compress_threshold_bytes=%s",
+                  yes_no(f->seal), yes_no(JOURNAL_FILE_COMPRESS(f)),
+                  format_bytes(bytes, sizeof(bytes), f->compress_threshold_bytes));
+
         if (mmap_cache)
                 f->mmap = mmap_cache_ref(mmap_cache);
         else {
@@ -3435,7 +3448,7 @@ fail:
         return r;
 }
 
-int journal_file_rotate(JournalFile **f, bool compress, bool seal, Set *deferred_closes) {
+int journal_file_rotate(JournalFile **f, bool compress, uint64_t compress_threshold_bytes, bool seal, Set *deferred_closes) {
         _cleanup_free_ char *p = NULL;
         size_t l;
         JournalFile *old_file, *new_file = NULL;
@@ -3489,7 +3502,9 @@ int journal_file_rotate(JournalFile **f, bool compress, bool seal, Set *deferred
          * we archive them */
         old_file->defrag_on_close = true;
 
-        r = journal_file_open(-1, old_file->path, old_file->flags, old_file->mode, compress, seal, NULL, old_file->mmap, deferred_closes, old_file, &new_file);
+        r = journal_file_open(-1, old_file->path, old_file->flags, old_file->mode, compress,
+                              compress_threshold_bytes, seal, NULL, old_file->mmap, deferred_closes,
+                              old_file, &new_file);
 
         if (deferred_closes &&
             set_put(deferred_closes, old_file) >= 0)
@@ -3506,6 +3521,7 @@ int journal_file_open_reliably(
                 int flags,
                 mode_t mode,
                 bool compress,
+                uint64_t compress_threshold_bytes,
                 bool seal,
                 JournalMetrics *metrics,
                 MMapCache *mmap_cache,
@@ -3517,7 +3533,8 @@ int journal_file_open_reliably(
         size_t l;
         _cleanup_free_ char *p = NULL;
 
-        r = journal_file_open(-1, fname, flags, mode, compress, seal, metrics, mmap_cache, deferred_closes, template, ret);
+        r = journal_file_open(-1, fname, flags, mode, compress, compress_threshold_bytes, seal, metrics, mmap_cache,
+                              deferred_closes, template, ret);
         if (!IN_SET(r,
                     -EBADMSG,           /* Corrupted */
                     -ENODATA,           /* Truncated */
@@ -3559,7 +3576,8 @@ int journal_file_open_reliably(
 
         log_warning_errno(r, "File %s corrupted or uncleanly shut down, renaming and replacing.", fname);
 
-        return journal_file_open(-1, fname, flags, mode, compress, seal, metrics, mmap_cache, deferred_closes, template, ret);
+        return journal_file_open(-1, fname, flags, mode, compress, compress_threshold_bytes, seal, metrics, mmap_cache,
+                                 deferred_closes, template, ret);
 }
 
 int journal_file_copy_entry(JournalFile *from, JournalFile *to, Object *o, uint64_t p, uint64_t *seqnum, Object **ret, uint64_t *offset) {