Ingo Molnar wrote:

* Theodore Tso [off-list ref] wrote:

quoted

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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