Re: PATCH: rewrite of invalidate_inode_pages

[Trond Myklebust <trond.myklebust@fys.uio.no>]

>>>>> " " == Juan J Quintela <quintela@fi.udc.es> writes:

     > Trond, I have not an SMP machine (yet), and I can not tell you
     > numbers now.  I put the counter there to show that we *may*
     > want to limit the latency there.  I am thinking in the write of
     > a big file, that can take a lot to free all the pages, but I

I'm pretty SMP-less myself at the moment (I'm visiting in Strasbourg
again), so I'm afraid I cannot run the test for you.

     > By the way, while we are here, the only difference between
     > truncate_inode_pages and invalidate_inode_pages is the one that
     > you told here before?  I am documenting some of the MM stuff,
     > and your comments in that aspect are really wellcome.  (You
     > will have noted now that I am quite newbie here).

Well. As far as NFS and other non-disk based systems are concerned
that is the functional difference between the two. That and the fact
that truncate_inode_pages() takes an offset as an argument.

For disk-based systems, they are very different beasts, since
truncate_inode_pages() will also attempt to invalidate and/or wait on
any pending buffers on the pages it clears out.

Strictly speaking therefore, one should not confuse the two, however
truncate_inode_pages() is (ab)used as a sleeping substitute for
invalidate_inode_pages() by some of the icache pruning code in
fs/inode.c.

Cheers,
  Trond
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