Messages in this thread | | | Date | Thu, 02 Sep 1999 20:46:12 +0200 | From | Manfred Spraul <> | Subject | Re: CONFIG_BIGMEM and rawio |
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Andrea Arcangeli wrote: > On Thu, 2 Sep 1999, Manfred wrote: > > >Im reading the BIGMEM codes, and it seems that BIGMEM and rawio are > >incompatible. > >Is that correct? > > The thing is not black and white. > [...] > Maybe it worth to add a per-blockdevice bitflag to allow raw-io on bigmem > pages with devices that uses DMA (such devices won't need any internal > change at all to work with bigmem pages, since with DMA only userspace and > the hardware device (and not the kernel) will touch the bigmem memory).
This sounds like a good idea.
> And you can _safely_ use raw-io in a _stock_ 2.3.16 with bigmem enabled > too; you won't risk to crash the kernel but you'll get a graceful -EIO in > the _worst_ case. But this means that all user mode programs which plan to use raw-io must support fall-back to normal io. Even worse, [buggy] programs would run on test machines [with less memory], and fail in actual production [with more memory]. A bitflags would be a good idea.
-- Manfred
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