From 4a92baf3fa97c73f04438b5814db58783f920b32 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 17 Jul 2012 00:36:15 +0200
Subject: journal: size journal data hash table based on maximum file size
 metrics

The default of 2047 hash table entries turned out to result in way too
many collisions for bigger files, hence scale the hash table size by the
estimated maximum file size.
---
 src/journal/journal-file.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

(limited to 'src/journal/journal-file.c')

diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index 9d8c9e686d..04564d989e 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -32,8 +32,8 @@
 #include "lookup3.h"
 #include "compress.h"
 
-#define DEFAULT_DATA_HASH_TABLE_SIZE (2047ULL*16ULL)
-#define DEFAULT_FIELD_HASH_TABLE_SIZE (2047ULL*16ULL)
+#define DEFAULT_DATA_HASH_TABLE_SIZE (2047ULL*sizeof(HashItem))
+#define DEFAULT_FIELD_HASH_TABLE_SIZE (333ULL*sizeof(HashItem))
 
 #define DEFAULT_WINDOW_SIZE (8ULL*1024ULL*1024ULL)
 
@@ -509,7 +509,17 @@ static int journal_file_setup_data_hash_table(JournalFile *f) {
 
         assert(f);
 
-        s = DEFAULT_DATA_HASH_TABLE_SIZE;
+        /* We estimate that we need 1 hash table entry per 2K of
+           journal file and we want to make sure we never get beyond
+           75% fill level. Calculate the hash table size for the
+           maximum file size based on these metrics. */
+
+        s = (f->metrics.max_size * 4 / 2048 / 3) * sizeof(HashItem);
+        if (s < DEFAULT_DATA_HASH_TABLE_SIZE)
+                s = DEFAULT_DATA_HASH_TABLE_SIZE;
+
+        log_info("Reserving %llu entries in hash table.", (unsigned long long) s);
+
         r = journal_file_append_object(f,
                                        OBJECT_DATA_HASH_TABLE,
                                        offsetof(Object, hash_table.items) + s,
@@ -1939,6 +1949,7 @@ int journal_file_open(
                 const char *fname,
                 int flags,
                 mode_t mode,
+                JournalMetrics *metrics,
                 JournalFile *template,
                 JournalFile **ret) {
 
@@ -1965,10 +1976,8 @@ int journal_file_open(
         f->writable = (flags & O_ACCMODE) != O_RDONLY;
         f->prot = prot_from_flags(flags);
 
-        if (template) {
-                f->metrics = template->metrics;
+        if (template)
                 f->compress = template->compress;
-        }
 
         f->path = strdup(fname);
         if (!f->path) {
@@ -2019,6 +2028,12 @@ int journal_file_open(
         }
 
         if (f->writable) {
+                if (metrics) {
+                        journal_default_metrics(metrics, f->fd);
+                        f->metrics = *metrics;
+                } else if (template)
+                        f->metrics = template->metrics;
+
                 r = journal_file_refresh_header(f);
                 if (r < 0)
                         goto fail;
@@ -2093,7 +2108,7 @@ int journal_file_rotate(JournalFile **f) {
 
         old_file->header->state = STATE_ARCHIVED;
 
-        r = journal_file_open(old_file->path, old_file->flags, old_file->mode, old_file, &new_file);
+        r = journal_file_open(old_file->path, old_file->flags, old_file->mode, NULL, old_file, &new_file);
         journal_file_close(old_file);
 
         *f = new_file;
@@ -2104,6 +2119,7 @@ int journal_file_open_reliably(
                 const char *fname,
                 int flags,
                 mode_t mode,
+                JournalMetrics *metrics,
                 JournalFile *template,
                 JournalFile **ret) {
 
@@ -2111,7 +2127,7 @@ int journal_file_open_reliably(
         size_t l;
         char *p;
 
-        r = journal_file_open(fname, flags, mode, template, ret);
+        r = journal_file_open(fname, flags, mode, metrics, template, ret);
         if (r != -EBADMSG && /* corrupted */
             r != -ENODATA && /* truncated */
             r != -EHOSTDOWN && /* other machine */
@@ -2140,7 +2156,7 @@ int journal_file_open_reliably(
 
         log_warning("File %s corrupted, renaming and replacing.", fname);
 
-        return journal_file_open(fname, flags, mode, template, ret);
+        return journal_file_open(fname, flags, mode, metrics, template, ret);
 }
 
 struct vacuum_info {
-- 
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