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

[Jeff Garzik]

Ingo Molnar wrote:
> * Theodore Tso <tytso@xxxxxxx> 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



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