From dd6263d3766eb6995ac30ca8c7bf652e2e05f9b0 Mon Sep 17 00:00:00 2001 From: sjc Date: Tue, 11 Apr 2017 01:33:42 -0700 Subject: [PATCH] commit resizeReplicationBacklog function --- src/replication.c | 34 ++++++++++++++++++---------------- 1 file changed, 18 insertions(+), 16 deletions(-) diff --git a/src/replication.c b/src/replication.c index b3a4294f2..b0ce99893 100644 --- a/src/replication.c +++ b/src/replication.c @@ -77,34 +77,36 @@ void createReplicationBacklog(void) { * server.repl_backlog_size and to resize the buffer and setup it so that * it contains the same data as the previous one (possibly less data, but * the most recent bytes, or the same data and more free space in case the - * buffer is enlarged). */ -// 动态调整 backlog 大小 -// 当 backlog 是被扩大时，原有的数据会被保留， -// 因为分配空间使用的是 realloc + * buffer is enlarged). + * me:在运行时调整backlog的大小 + * me:注意 上面的注释与源码对应不上。resize后会释放原来的缓冲区。 + */ void resizeReplicationBacklog(long long newsize) { - // 不能小于最小大小 - if (newsize < REDIS_REPL_BACKLOG_MIN_SIZE) - newsize = REDIS_REPL_BACKLOG_MIN_SIZE; - - // 大小和目前大小相等 - if (server.repl_backlog_size == newsize) return; - + if (newsize < CONFIG_REPL_BACKLOG_MIN_SIZE) + newsize = CONFIG_REPL_BACKLOG_MIN_SIZE; + if (server.repl_backlog_size == newsize) return; //两者相等 无需重设 + // 设置新大小 - server.repl_backlog_size = newsize; + server.repl_backlog_size = newsize; if (server.repl_backlog != NULL) { /* What we actually do is to flush the old buffer and realloc a new * empty one. It will refill with new data incrementally. * The reason is that copying a few gigabytes adds latency and even * worse often we need to alloc additional space before freeing the - * old buffer. */ + * old buffer. + * 我们是这样做的：清除老的buffer，重新分配一个空的buffer。新的buffer + * 将被新的数据填充。这样做的原因是:复制几G数据会有延时，更糟糕的是, + * 我们常常需要分配额外的内存空间，在释放老的buffer之前。 + * + */ // 释放 backlog - zfree(server.repl_backlog); + zfree(server.repl_backlog); //调用free // 按新大小创建新 backlog - server.repl_backlog = zmalloc(server.repl_backlog_size); + server.repl_backlog = zmalloc(server.repl_backlog_size); //调用malloc分配内存 server.repl_backlog_histlen = 0; server.repl_backlog_idx = 0; - /* Next byte we have is... the next since the buffer is emtpy. */ + /* Next byte we have is... the next since the buffer is empty. */ server.repl_backlog_off = server.master_repl_offset+1; } }