Re: [PATCH 00/23] per device dirty throttling -v8

Jeff Garzik
2007-08-05T17:59:58Z

Ingo Molnar wrote:
> * Theodore Tso <tytso@mit.edu> wrote:
>
>> If you are always reading from the same small set of files (i.e., a
>> database workload), then those inodes only get updated every 5 seconds
>> (the traditional/default metadata update sync time, as well as the
>> default ext3 journal update time), it's no big deal. Or if you are
>> running a mail server, most of the time the mail queue files are
>> getting updated anyway as you process them, and usually the mail is
>> delivered before 5 seconds is up anyway.
>>
>> So earlier, when Ingo characterized it as, "whenever you read from a
>> file, even one in memory cache.... do a write!", it's probably a bit
>> unfair. Traditional Unix systems simply had very different workload
>> characteristics than many modern dekstop systems today.
>
> yeah, i didnt mean to say that it is _always_ a big issue, but "only a
> small number of files are read" is a very, very small minority of even
> the database server world.

OTOH, consider a popular Linux task, web serving. atime results in a
lot of unnecessary disk traffic.

Jeff