>> "H. Peter Anvin" <hpa@transmeta.com> writes:
>> >
>> > bdflush yes, but update is not obsolete.
>> >
>> > It is still needed if you want to make sure data (and metadata)
>> > eventually gets written to disk.
>> >
>> > Of course, you can run without update, but then don't bother if you
>> > lose file in system crash, even if you edited it and saved it few
>> > hours ago. :)
>> >
>> > Update is very important if you have lots of RAM in your computer.
>> >
>>
>> Oh. I guess my next question then is "why", as why can't this be done
>> by kflushd as well?
>>
>> To tell you the truth, I'm not sure why, these days.
>> I thought it was done this way (update running in userspace) so to
>> have control how often buffers get flushed. But, I believe bdflush
>> program had this functionality, and it is long gone (as you correctly
>> noticed).
IMHO, update/bdflush (in user space) calls sys_bdflush regularly. This
function (fs/buffer.c) calls sync_old_buffers() which itself sync_supers
and sync_inodes before it goes through the dirty buffer lust (to write
some dirty buffers); the kflushd only writes some dirty buffers dependent
on the sysctl parameters.
If I'm wrong, please feel free to correct me!
Regards
Bernhard
get my pgp key from a public keyserver (keyID=0x62446355)
-----------------------------------------------------------------------------
Bernhard Heidegger bheide@hyperwave.com
Hyperwave Software Research & Development
Schloegelgasse 9/1, A-8010 Graz
Voice: ++43/316/820918-25 Fax: ++43/316/820918-99
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