1. 21 Jul, 2016 3 commits
    • antirez's avatar
      Avoid simultaneous RDB and AOF child process. · 0a628e51
      antirez authored
      This patch, written in collaboration with Oran Agra (@oranagra) is a companion
      to 780a8b1d. Together the two patches should avoid that the AOF and RDB saving
      processes can be spawned at the same time. Previously conditions that
      could lead to two saving processes at the same time were:
      
      1. When AOF is enabled via CONFIG SET and an RDB saving process is
         already active.
      
      2. When the SYNC command decides to start an RDB saving process ASAP in
         order to serve a new slave that cannot partially resynchronize (but
         only if we have a disk target for replication, for diskless
         replication there is not such a problem).
      
      Condition "1" is not very severe but "2" can happen often and is
      definitely good at degrading Redis performances in an unexpected way.
      
      The two commits have the effect of always spawning RDB savings for
      replication in replicationCron() instead of attempting to start an RDB
      save synchronously. Moreover when a BGSAVE or AOF rewrite must be
      performed, they are instead just postponed using flags that will try to
      perform such operations ASAP.
      
      Finally the BGSAVE command was modified in order to accept a SCHEDULE
      option so that if an AOF rewrite is in progress, when this option is
      given, the command no longer returns an error, but instead schedules an
      RDB rewrite operation for when it will be possible to start it.
      0a628e51
    • antirez's avatar
      Replication: start BGSAVE for replication always in replicationCron(). · 780a8b1d
      antirez authored
      This makes the replication code conceptually simpler by removing the
      synchronous BGSAVE trigger in syncCommand(). This also means that
      socket and disk BGSAVE targets are handled by the same code.
      780a8b1d
    • antirez's avatar
      e0582b35
  2. 20 Jul, 2016 3 commits
  3. 18 Jul, 2016 5 commits
  4. 15 Jul, 2016 1 commit
  5. 14 Jul, 2016 4 commits
    • antirez's avatar
      LFU simulator: remove dead code. · ada70c7c
      antirez authored
      ada70c7c
    • antirez's avatar
      LRU simulator: fix new entry creation decr time. · fc92c667
      antirez authored
      fc92c667
    • antirez's avatar
      LRU simulator: fix new entry creation. · f50dc38b
      antirez authored
      f50dc38b
    • antirez's avatar
      LFU: Simulation of the algorithm planned for Redis. · 09fcb002
      antirez authored
      We have 24 total bits of space in each object in order to implement
      an LFU (Least Frequently Used) eviction policy.
      
      We split the 24 bits into two fields:
      
            8 bits      16 bits
          +--------+----------------+
          | LOG_C  | Last decr time |
          +--------+----------------+
      
      LOG_C is a logarithmic counter that provides an indication of the access
      frequency. However this field must also be deceremented otherwise what used
      to be a frequently accessed key in the past, will remain ranked like that
      forever, while we want the algorithm to adapt to access pattern changes.
      
      So the remaining 16 bits are used in order to store the "decrement time",
      a reduced-precision unix time (we take 16 bits of the time converted
      in minutes since we don't care about wrapping around) where the LOG_C
      counter is halved if it has an high value, or just decremented if it
      has a low value.
      
      New keys don't start at zero, in order to have the ability to collect
      some accesses before being trashed away, so they start at COUNTER_INIT_VAL.
      The logaritmic increment performed on LOG_C takes care of COUNTER_INIT_VAL
      when incrementing the key, so that keys starting at COUNTER_INIT_VAL
      (or having a smaller value) have a very high chance of being incremented
      on access.
      
      The simulation starts with a power-law access pattern, and later converts
      into a flat access pattern in order to see how the algorithm adapts.
      Currenty the decrement operation period is 1 minute, however note that
      it is not guaranteed that each key will be scanned 1 time every minute,
      so the actual frequency can be lower. However under high load, we access
      3/5 keys every newly inserted key (because of how Redis eviction works).
      
      This is a work in progress at this point to evaluate if this works well.
      09fcb002
  6. 13 Jul, 2016 1 commit
    • antirez's avatar
      LRU: Make cross-database choices for eviction. · e423f76e
      antirez authored
      The LRU eviction code used to make local choices: for each DB visited it
      selected the best key to evict. This was repeated for each DB. However
      this means that there could be DBs with very frequently accessed keys
      that are targeted by the LRU algorithm while there were other DBs with
      many better candidates to expire.
      
      This commit attempts to fix this problem for the LRU policy. However the
      TTL policy is still not fixed by this commit. The TTL policy will be
      fixed in a successive commit.
      
      This is an initial (partial because of TTL policy) fix for issue #2647.
      e423f76e
  7. 12 Jul, 2016 5 commits
  8. 11 Jul, 2016 4 commits
  9. 06 Jul, 2016 13 commits
  10. 05 Jul, 2016 1 commit
    • antirez's avatar
      redis-cli: check SELECT reply type just in state updated. · ef6a4df2
      antirez authored
      In issues #3361 / #3365 a problem was reported / fixed with redis-cli
      not updating correctly the current DB on error after SELECT.
      
      In theory this bug was fixed in 0042fb0e, but actually the commit only
      fixed the prompt updating, not the fact the state was set in a wrong
      way.
      
      This commit removes the check in the prompt update, now that hopefully
      it is the state that is correct, there is no longer need for this check.
      ef6a4df2