commit cb6c909664f97f751fe78c0aa3205a9042760c53 Author: Nick Mathewson nickm@torproject.org Date: Tue May 3 17:03:49 2011 -0400

Rebuild the microdesc cache when a sufficient number of bytes are dropped

Previously on 0.2.2, we'd never clean the cache. Now that we can clean it, we want to add a condition to rebuild it: that should happen whenever we have dropped enough microdescriptors that we could save a lot of space.

No changes file, since 0.2.3 doesn't need one and 0.2.2 already has some changes files for the backport of the microdesc_clean_cahce() function. --- src/or/microdesc.c | 45 +++++++++++++++++++++++++++++++++------------ src/or/microdesc.h | 2 +- 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/src/or/microdesc.c b/src/or/microdesc.c index 58fbe37..c6bb3c6 100644 --- a/src/or/microdesc.c +++ b/src/or/microdesc.c @@ -177,6 +177,8 @@ microdescs_add_list_to_cache(microdesc_cache_t *cache, if (md2->last_listed < md->last_listed) md2->last_listed = md->last_listed; microdesc_free(md); + if (where != SAVED_NOWHERE) + cache->bytes_dropped += size; continue; }

@@ -206,14 +208,7 @@ microdescs_add_list_to_cache(microdesc_cache_t *cache, if (f) finish_writing_to_file(open_file); /*XXX Check me.*/

- { - size_t old_content_len = - cache->cache_content ? cache->cache_content->size : 0; - if (cache->journal_len > 16384 + old_content_len && - cache->journal_len > old_content_len / 2) { - microdesc_cache_rebuild(cache); - } - } + microdesc_cache_rebuild(cache, 0/* only as needed */);

return added; } @@ -275,6 +270,9 @@ microdesc_cache_reload(microdesc_cache_t *cache) } log_notice(LD_DIR, "Reloaded microdescriptor cache. Found %d descriptors.", total); + + microdesc_cache_clean(cache, 0, 0); + return 0; }

@@ -323,11 +321,30 @@ microdesc_cache_clean(microdesc_cache_t *cache, time_t cutoff, int force) } }

+static int +should_rebuild_md_cache(microdesc_cache_t *cache) +{ + const size_t old_len = + cache->cache_content ? cache->cache_content->size : 0; + const size_t journal_len = cache->journal_len; + const size_t dropped = cache->bytes_dropped; + + if (journal_len < 16384) + return 0; /* Don't bother, not enough has happened yet. */ + if (dropped > (journal_len + old_len) / 3) + return 1; /* We could save 1/3 or more of the currently used space. */ + if (journal_len > old_len / 2) + return 1; /* We should append to the regular file */ + + return 0; +} + /** Regenerate the main cache file for <b>cache</b>, clear the journal file, * and update every microdesc_t in the cache with pointers to its new - * location. */ + * location. If <b>force</b> is true, do this unconditionally. If + * <b>force</b> is false, do it only if we expect to save space on disk. */ int -microdesc_cache_rebuild(microdesc_cache_t *cache) +microdesc_cache_rebuild(microdesc_cache_t *cache, int force) { open_file_t *open_file; FILE *f; @@ -337,11 +354,14 @@ microdesc_cache_rebuild(microdesc_cache_t *cache) off_t off = 0; int orig_size, new_size;

- log_info(LD_DIR, "Rebuilding the microdescriptor cache..."); - /* Remove dead descriptors */ microdesc_cache_clean(cache, 0/*cutoff*/, 0/*force*/);

+ if (!force && !should_rebuild_md_cache(cache)) + return 0; + + log_info(LD_DIR, "Rebuilding the microdescriptor cache..."); + orig_size = (int)(cache->cache_content ? cache->cache_content->size : 0); orig_size += (int)cache->journal_len;

@@ -396,6 +416,7 @@ microdesc_cache_rebuild(microdesc_cache_t *cache)

write_str_to_file(cache->journal_fname, "", 1); cache->journal_len = 0; + cache->bytes_dropped = 0;

new_size = (int)cache->cache_content->size; log_info(LD_DIR, "Done rebuilding microdesc cache. " diff --git a/src/or/microdesc.h b/src/or/microdesc.h index 30cb25d..77ce853 100644 --- a/src/or/microdesc.h +++ b/src/or/microdesc.h @@ -22,7 +22,7 @@ smartlist_t *microdescs_add_list_to_cache(microdesc_cache_t *cache, int no_save);

void microdesc_cache_clean(microdesc_cache_t *cache, time_t cutoff, int force); -int microdesc_cache_rebuild(microdesc_cache_t *cache); +int microdesc_cache_rebuild(microdesc_cache_t *cache, int force); int microdesc_cache_reload(microdesc_cache_t *cache); void microdesc_cache_clear(microdesc_cache_t *cache);