Messages in this thread | | | Date | Tue, 27 Apr 2004 18:38:00 -0700 | From | Andrew Morton <> | Subject | Re: 2.6.6-rc{1,2} bad VM/NFS interaction in case of dirty page writeback |
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Trond Myklebust <trond.myklebust@fys.uio.no> wrote: > > On Tue, 2004-04-27 at 21:02, Andrew Morton wrote: > > Shantanu Goel <sgoel01@yahoo.com> wrote: > > > > > > Andrew/Trond, > > > > > > Any consensus as to what the right approach is here? > > > > For now I suggest you do > > > > - err = WRITEPAGE_ACTIVATE; > > + err = 0; > > > > in nfs_writepage(). > > That will just cause the page to be put back onto the inactive list > without starting writeback. Won't that cause precisely those kswapd > loops that Shantanu was worried about?
Possibly - but the process which is in reclaim will throttle and will kick pdflush which will do the writepages() thing.
It needs testing.
> AFAICS if you want to do this, you probably need to flush the page > immediately to disk on the server using a STABLE write as per the > appeanded patch. The problem is that screws the server over pretty hard > as it will get flooded with what are in effect a load of 4k O_SYNC > writes.
Well I'd be interested in discovering which workloads actually suffer significantly from doing this. If it's a significant problem then perhaps we should resurrect the writearound-from-within-writepage thing. It's pretty simple to do, especially since we now have efficient ways of finding neighbouring dirty pages.
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