On March 8, the system of data caching in RAM was updated Memcached up to version 1.6.0. The main difference from previous releases is that now it has become possible to use an external device for the cached data store.
Memcached used to speed up the work of highly loaded sites or web applications by caching access to the DBMS and intermediate data.
In the new version, when building, the parameter is enabled by default extstore, which is responsible for the use of external media. To disable the feature, specify the --disable-extstore option in ./configure. However, despite the default build at startup, you should explicitly specify the use of this function.
Extstore allows the use of external Flash or SSD drive to increase the cache size. This will allow much larger amounts of data to be cached than without using this feature.
Another important innovation was the processing of networking, which is now adapted for automatic processing of batch requests within a single system call. In previous versions, the processing of each GET request was transmitted in a separate package, while in the new version, responses to multiple requests are collected in one metapacket and transmitted at one time. As a result of this innovation, the load on the CPU was reduced by 25%.
Also, as a result of this upgrade, memory consumption for buffering was reduced - from 4.5 KB to 400-500 bytes per call, and the use of malloc, realloc and free functions was reduced, which led to less memory fragmentation. Each thread now handles its own read and write buffer pool for active connections. The options -o resp_obj_mem_limit=N and -o read_buf_mem_limt=N are provided to adjust the size of these buffers.
It was also announced that the binary protocol for exchanging with the server was degraded. It was replaced by the meta protocol - a text version of the protocol with compact meta commands. The new protocol takes into account all previously available operations using the old versions of the binary protocol.
>>> Official site
>>> Source (BSD license)
>>> Description of meta commands
Source: linux.org.ru