| Bug #64353 | mysql_binlog_send calls malloc/free for every event sent to a slave | ||
|---|---|---|---|
| Submitted: | 16 Feb 2012 15:45 | Modified: | 29 Dec 2012 21:56 |
| Reporter: | Mark Callaghan | Email Updates: | |
| Status: | Duplicate | Impact on me: | |
| Category: | MySQL Server: Replication | Severity: | S5 (Performance) |
| Version: | 5.1.52 | OS: | Any |
| Assigned to: | CPU Architecture: | Any | |
| Tags: | Contribution | ||
[16 Feb 2012 15:45]
Mark Callaghan
patch to reduce malloc/free calls
Attachment: reb.patch (application/octet-stream, text), 9.73 KiB.
[23 Apr 2012 6:23]
zhai weixiang
hi, Mark i had tried to merge your patch into Percona Server5.5.18 , and after a simple test (use vmstat to watch CPU usage ), i found the CPU usage was not improved. i don't know if i had test the patch in a wrong way. so can you provide more information about your test?
[23 Apr 2012 14:18]
Mark Callaghan
It depends on your workload. A busy server with large binlog events and many slave connections and a high rate of transactions and many CPU cores is the best way to reproduce the possible benefit.
[24 Apr 2012 1:51]
zhai weixiang
thank you very much for your advise, Mark. I will follow your suggestion to test. :)
[29 Dec 2012 21:56]
Erlend Dahl
This is a duplicate of an internally filed feature request.
Description: Apply this patch reduced CPU by ~5%. The host had 5 slave connections. The patch comes from the big Google diff for MySQL 5.0.37 mysql_binlog_send calls malloc/free for every event sent to a slave. The buffer, "packet", is initialized with a buffer provided by the caller prior to reading an event: packet->set("\0", 1, &my_charset_bin); That free's the old buffer it was using and then initializes it to use a buffer that won't be freed. Any appends that follow will require it to allocate/reallocate memory, thus more calls to malloc/free/realloc. /** Points the internal buffer to the supplied one. The old buffer is freed. @param str Pointer to the new buffer. @param arg_length Length of the new buffer in characters, excluding any null character. @param cs Character set to use for interpreting string data. @note The new buffer will not be null terminated. */ inline void set(char *str,uint32 arg_length, CHARSET_INFO *cs) { free(); Ptr=(char*) str; str_length=Alloced_length=arg_length ; alloced=0; str_charset=cs; } How to repeat: Read the code, apply the patch and notice that malloc/free are called less frequently and CPU load should be reduced. Suggested fix: Allocate a buffer and reuse it in the while loop.