diff options
| author | Matthias Radestock <matthias@rabbitmq.com> | 2014-03-03 16:35:45 +0000 |
|---|---|---|
| committer | Matthias Radestock <matthias@rabbitmq.com> | 2014-03-03 16:35:45 +0000 |
| commit | 303eca58d45ee72467a6eebbe08ee51fbaaad029 (patch) | |
| tree | 2a347f694cff13b83ee5dbb30a1feb15716e40ae | |
| parent | a0b046de111331fa8227c12fb3990a7744e60323 (diff) | |
| download | rabbitmq-server-git-303eca58d45ee72467a6eebbe08ee51fbaaad029.tar.gz | |
explain (reduced) impact of IO_BATCH_SIZE
| -rw-r--r-- | src/rabbit_variable_queue.erl | 21 |
1 files changed, 7 insertions, 14 deletions
diff --git a/src/rabbit_variable_queue.erl b/src/rabbit_variable_queue.erl index c1a18a7400..711cced613 100644 --- a/src/rabbit_variable_queue.erl +++ b/src/rabbit_variable_queue.erl @@ -164,13 +164,12 @@ %% converting a batch stalls the queue for too long. Therefore, it %% must be just right. %% -%% The conversion from alphas to betas is also chunked, but only to -%% ensure no more than ?IO_BATCH_SIZE alphas are converted to betas at -%% any one time. This further smooths the effects of changes to the -%% target_ram_count and ensures the queue remains responsive -%% even when there is a large amount of IO work to do. The -%% timeout callback is utilised to ensure that conversions are -%% done as promptly as possible whilst ensuring the queue remains +%% The conversion from alphas to betas is chunked due to the +%% credit_flow limits of the msg_store. This further smooths the +%% effects of changes to the target_ram_count and ensures the queue +%% remains responsive even when there is a large amount of IO work to +%% do. The 'resume' callback is utilised to ensure that conversions +%% are done as promptly as possible whilst ensuring the queue remains %% responsive. %% %% In the queue we keep track of both messages that are pending @@ -196,13 +195,7 @@ %% The order in which alphas are pushed to betas and pending acks %% are pushed to disk is determined dynamically. We always prefer to %% push messages for the source (alphas or acks) that is growing the -%% fastest (with growth measured as avg. ingress - avg. egress). In -%% each round of memory reduction a chunk of messages at most -%% ?IO_BATCH_SIZE in size is allocated to be pushed to disk. The -%% fastest growing source will be reduced by as much of this chunk as -%% possible. If there is any remaining allocation in the chunk after -%% the first source has been reduced to zero, the second source will -%% be reduced by as much of the remaining chunk as possible. +%% fastest (with growth measured as avg. ingress - avg. egress). %% %% Notes on Clean Shutdown %% (This documents behaviour in variable_queue, queue_index and |