On Thu, 11 Jun 2009, Yinghai Lu wrote:
> On Thu, Jun 11, 2009 at 7:21 AM, Thomas Gleixner<tglx@xxxxxxxxxxxxx> wrote:
> > On Thu, 11 Jun 2009, Andreas Herrmann wrote:
> > But the reserve_bad_mem() semantics are even more scary:
> >
> > - if you hit flaky memory, which gives you bad and good results here
> > and there, you call reserve_bad_mem() totally unbound which is
> > likely to overflow the early reservation space and panics the
> > machine. You need to keep track of those events somehow (e.g. in a
> > bitmap) so you can detect such problems and mark the whole affected
> > region bad in one go.
>
> if one pass found bad, it is reserved.
> second pass will use find_e820_area_size() to get new range, so bad
> one will not be used.
No, that's not about passes. Assume that you have flaky memory which
works halfways. So that code runs through a full memory region from 0
to 0x1000000.
0-FF OK
100-1ff BAD
200-21f OK
220-23f BAD
....
So there is no find_e820_area_size() between those OK/BAD steps, but
every new BAD hit calls reserve_early() and you run out of space in
the reserve array.
> > - you call reserve_early() which calls __reserve_early(....,
> > overrun_ok = 0) so if you do the default multi pattern scan and each
> > run sees the same region of broken memory you will trigger the
> > "Overlapping early reservations" panic in __reserve_early() when you
> > reserve that region the second time. Why do you run the test twice
> > when the first one failed already ? Also there is no need to do the
> > wipeout run in that case, which will trigger it as well!
Ok, here applies the find_e820_area_size() thing. I missed that
because the code is so well documented and obvious.
> current problem in that: we could run out of res_reserve array.
> solution will be make res_reserve array dynamically.
> when can not find slot, need use find_e820_area to get double sized,
> and copy the old to new one.
> then free the old one.
This applies to the first problem, which can be avoided by clever
coding.
Thanks,
tglx
--
To unsubscribe from this list: send the line "unsubscribe linux-next" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
