Attachment 79382 Details for Bug 64616 – Ttry to avoid binary search when looking up by seqnum.

[patch] Ttry to avoid binary search when looking up by seqnum.

0001-journal-try-to-predict-the-index-when-looking-up-an-.patch (text/plain), 1.58 KB, created by Marius Vollmer on 2013-05-16 07:21:24 UTC

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Creator: Marius Vollmer

Created: 2013-05-16 07:21:24 UTC

Size: 1.58 KB

patch

obsolete

>From 7c0728230f65679e7c1b8039bb9dbf8c828ac9d2 Mon Sep 17 00:00:00 2001
>From: Marius Vollmer <mvollmer@redhat.com>
>Date: Thu, 16 May 2013 09:59:57 +0300
>Subject: [PATCH] journal: try to predict the index when looking up an entry by
> seqnum
>
>---
> src/journal/journal-file.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
>diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
>index 38499a6..71bfe59 100644
>--- a/src/journal/journal-file.c
>+++ b/src/journal/journal-file.c
>@@ -1767,6 +1767,24 @@ int journal_file_move_to_entry_by_seqnum(
>                 Object **ret,
>                 uint64_t *offset) {
> 
>+        /* Most of the time, the entry with sqenum S is found at index
>+         * S-1, so we try that first.  This is faster and might even
>+         * allow us to survive a corrupted journal file that would
>+         * otherwise trip up the binary search.
>+         */
>+        if (seqnum >= 1 && seqnum <= f->header->n_entries) {
>+                Object *o;
>+                if (generic_array_get(f,
>+                                      le64toh(f->header->entry_array_offset),
>+                                      seqnum-1,
>+                                      &o, offset) >= 0 &&
>+                    le64toh(o->entry.seqnum) == seqnum) {
>+                        if (ret)
>+                                *ret = o;
>+                        return 1;
>+                }
>+        }
>+
>         return generic_array_bisect(f,
>                                     le64toh(f->header->entry_array_offset),
>                                     le64toh(f->header->n_entries),
>-- 
>1.8.1.4
>

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