On Mon, Sep 18, 2017 at 2:41 PM, 关云飞 <seven.guanyunfei@xxxxxxxxxx> wrote: > > hello kefu chai, > > > These two days I carefully considered the pr https://github.com/ceph/ceph/pull/17661 and looked the code about bufferlist and I still think the steps of 1-3 > is needed. Although the ptr::_off can guarantee bufferlist to be copied/read/decode/write_file rightly, this will lead a bufferlist not clean and will waste memory > like picture below. > > Of course, it's also possible that i am not thinking about it, do you have any suggestions? i think it's the user of the bufferlist's choice to defrag the element(s) in it or not. and it's not a pure win: it hurts the performance in some cases. in the case of PR#17661, we are trying to realloc a smaller mem chunk to replace the first memory ptr with it, if it has "bubbles". what about the second element, or the third one in the buffer::list, shall we also take care of them as well? -- Regards Kefu Chai -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
