Home > Erlang探索 > ETS新的压缩特性

ETS新的压缩特性

November 28th, 2010 Leave a comment Go to comments

原创文章,转载请注明: 转载自系统技术非业余研究

本文链接地址: ETS新的压缩特性

即将发布的R14B01要支持ets的压缩,更大程度的提高内存的利用率。
在github上可以看到这个分支,有兴趣的同学可以下载下来看看。

压缩的时候只压缩value, key是不压缩的。 value特别简单类型的eterm也是不压缩的,因为zip压缩需要一定长度的内容,而且压缩本身也要加入一点的overload.

以下是sverker (author)的提交log.

ETS ‘compressed’ option.

The compressed format is using a slighty modified variant of the extern format
(term_to_binary). To not worsen key lookup’s too much, the top tuple itself
and the key element are not compressed. Table objects with only immediate
non-key elements will therefor not gain anything (but actually consume one
extra word for “alloc_size”).

我们来试验下吧:

# erl +ec
Erlang R14B01 (erts-5.8.2) [/source] [64-bit] [smp:48:48] [rq:48] [async-threads:0] [hipe] [kernel-poll:false]

Eshell V5.8.2  (abort with ^G)
1> ets:all().
[8207,4110,13,file_io_servers,inet_hosts_file_byaddr,
 inet_hosts_file_byname,inet_hosts_byaddr,inet_hosts_byname,
 inet_cache,inet_db,global_pid_ids,global_pid_names,
 global_names_ext,global_names,global_locks,ac_tab]
2> ets:info(8207).
[{compressed,true},
 {memory,92},
 {owner,<0.26.0>},
 {heir,none},
 {name,shell_records},
 {size,0},
 {node,nonode@nohost},
 {named_table,false},
 {type,ordered_set},
 {keypos,1},
 {protection,public}]
3> ets:new(xx, [public, compressed]).
16400
4> ets:info(16400).                  
[{compressed,true},
 {memory,302},
 {owner,<0.32.0>},
 {heir,none},
 {name,xx},
 {size,0},
 {node,nonode@nohost},
 {named_table,false},
 {type,set},
 {keypos,1},
 {protection,public}]

祝大家玩的开心。

Post Footer automatically generated by wp-posturl plugin for wordpress.

Categories: Erlang探索 Tags: ,
  1. dogtap
    January 6th, 2011 at 19:41 | #1

    —压缩前——
    [{compressed,false},
    {memory,2795863},
    {owner,},
    {heir,none},
    {name,ets_scene_poses},
    {size,275615},
    {node,’xge2@192.168.1.108′},
    {named_table,true},
    {type,set},
    {keypos,1},
    {protection,protected}]
    ———-压缩后———–
    [{compressed,true},
    {memory,3071478},
    {owner,},
    {heir,none},
    {name,ets_scene_poses},
    {size,275615},
    {node,’xge2@192.168.1.108′},
    {named_table,true},
    {type,set},
    {keypos,1},
    {protection,protected}]
    ———–
    本地xp 的开发机,压缩后反而内存长了,为什么呢?

    [Reply]

    Yu Feng Reply:

    1. 压缩的对象他挑的,不一定所有的类型都可压缩的。
    2. 可压缩的对象的内容是不是有压缩率。
    3. 压缩要管理成本。

    [Reply]

  2. dogtap
    January 6th, 2011 at 20:40 | #2

    博主回复真快,看来只能在有string 类型的table 里面试验了。

    [Reply]

  1. No trackbacks yet.