Just a guess : wouldn't it be because the log files on disk can be made of
compressed data when produced but needs to be uncompressed on consumption
(of a single message) ?

2018-02-12 15:50 GMT+01:00 YuFeng Shen <v...@hotmail.com>:

> Hi jan ,
> I think the reason is the same as why index file using  memory mapped file.
> As the memory mapped file can avoid the data copy between user and kernel
> buffer space, so it can improve the performance for the index file IO
> operation ,right? If it is ,why Log file cannot achieve the same
> performance improvement as memory mapped index file?
> Jacky
> ________________________________
> From: jan <rtm4...@googlemail.com>
> Sent: Saturday, February 10, 2018 8:33 PM
> To: users@kafka.apache.org
> Subject: Re: why kafka index file use memory mapped files ,however log
> file doesn't
> I'm not sure I can answer your question, but may I pose another in
> return: why do you feel having a memory mapped log file would be a
> good thing?
> On 09/02/2018, YuFeng Shen <v...@hotmail.com> wrote:
> > Hi Experts,
> >
> > We know that kafka use memory mapped files for it's index files ,however
> > it's log files don't use the memory mapped files technology.
> >
> > May I know why index files use memory mapped files, however log files
> don't
> > use the same technology?
> >
> >
> > Jacky
> >

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