Messages in this thread | | | Date | Fri, 26 Jun 2020 15:24:26 -0400 | From | Qian Cai <> | Subject | Re: [PATCH] mm/vmscan: restore zone_reclaim_mode ABI |
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On Thu, Jun 25, 2020 at 05:34:59PM -0700, Dave Hansen wrote: > > From: Dave Hansen <dave.hansen@linux.intel.com> > > I went to go add a new RECLAIM_* mode for the zone_reclaim_mode > sysctl. Like a good kernel developer, I also went to go update the > documentation. I noticed that the bits in the documentation didn't > match the bits in the #defines. > > The VM evidently stopped caring about RECLAIM_ZONE at some point (or > never cared) and the #define itself was later removed as a cleanup. > Those things by themselves are fine. > > But, the _other_ bit locations also got changed. That's not OK because > the bit values are documented to mean one specific thing and users > surely rely on them meaning that one thing and not changing from > kernel to kernel. The end result is that if someone had a script > that did: > > sysctl vm.zone_reclaim_mode=1 > > That script went from doing nothing to writing out pages during > node reclaim after the commit in question. That's not great. > > Put the bits back the way they were and add a comment so something > like this is a bit harder to do again. Update the documentation to > make it clear that the first bit is ignored. > > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> > Fixes: commit 648b5cf368e0 ("mm/vmscan: remove unused RECLAIM_OFF/RECLAIM_ZONE")
This is a wrong format.
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