Messages in this thread | | | Subject | Re: per-bdi-throttling: synchronous writepage doesn't work correctly | From | Peter Zijlstra <> | Date | Thu, 01 Nov 2007 18:09:09 +0100 |
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On Thu, 2007-11-01 at 18:00 +0100, Miklos Szeredi wrote: > > > Hi, > > > > > > It looks like bdi_thresh will always be zero if filesystem does > > > synchronous writepage, resulting in very poor write performance. > > > > > > Hostfs (UML) is one such example, but there might be others. > > > > > > The only solution I can think of is to add a set_page_writeback(); > > > end_page_writeback() pair (or some reduced variant, that only does > > > the proportions magic). But that means auditing quite a few > > > filesystems... > > > > Ouch... > > > > I take it there is no other function that is shared between all these > > writeout paths which we could stick a bdi_writeout_inc(bdi) in? > > No, and you can't detect it from the callers either I think.
The page not having PG_writeback set on return is a hint, but not fool proof, it could be the device is just blazing fast.
I guess there is nothing to it but for me to grep writepage and manually look at all hits...
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