Messages in this thread | | | Subject | Re: [PATCH v2 5/5] dax: handle media errors in dax_do_io | From | Toshi Kani <> | Date | Fri, 15 Apr 2016 13:01:49 -0600 |
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On Fri, 2016-04-15 at 11:17 -0700, Dan Williams wrote: > On Fri, Apr 15, 2016 at 11:06 AM, Jeff Moyer <jmoyer@redhat.com> wrote: > > > > Dan Williams <dan.j.williams@intel.com> writes: > > > > > > > There's a lot of special casing here, so you might consider > > > > > adding comments. > > > > Correct - maybe we should reconsider wrapper-izing this? :) > > > Another option is just to skip dax_do_io() and this special casing > > > fallback entirely if errors are present. I.e. only attempt dax_do_io > > > when: IS_DAX() && gendisk->bb && bb->count == 0. > > > > So, if there's an error anywhere on the device, penalize all I/O (not > > just writes, and not just on sectors that are bad)? I'm not sure > > that's a great plan, either. > > > If errors are rare how much are we actually losing in practice? > Moreover, we're going to do the full badblocks lookup anyway when we > call ->direct_access(). If we had that information earlier we can > avoid this fallback dance.
A system running with DAX may have active data set in NVDIMM lager than RAM size. In this case, falling back to non-DAX will allocate page cache for the data, which will saturate the system with memory pressure.
Thanks, -Toshi
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