Messages in this thread | | | Subject | Re: RFC on io-stalls patch | From | Chris Mason <> | Date | 12 Jul 2003 14:37:40 -0400 |
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On Fri, 2003-07-11 at 20:20, Nick Piggin wrote:
> >Seems that way. With the 2.4.21 code, a read might easily get a > >request, but then spend forever waiting for a huge queue of merged > >writes to get to disk. > > > > But it is the job of the io scheduler to prevent this, isn't it? >
Yes, but the 2.4.21 code doesn't do it.
> > > >I believe the new way provides better overall read performance in the > >presence of lots of writes. > > > > > > I don't know how that can be, considering writers will consume > basically limitless requests. What am I missing?
There is a limit on the total amount of IO in flight (4MB by default, reads/writes combined). We can make this a harder limit by disallowing merges on any requests present at the time of an unplug. Perhaps I'm not reading your question correctly?
-chris
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