On Tue, Sep 13, 2022 at 12:32:50PM +0530, Anshuman Khandual wrote:
>
>
> On 9/9/22 14:54, Miaohe Lin wrote:
> > If ALLOC_KSWAPD is set, wake_all_kswapds() will be called to ensure
> > kswapd doesn't accidentally go to sleep. But when reserve_flags is
> > set, alloc_flags will be overwritten and ALLOC_KSWAPD is thus lost.
> > Preserve the ALLOC_KSWAPD flag in alloc_flags to ensure kswapd won't
> > go to sleep accidentally.
>
> Currently wake_all_kswapds() gets skipped subsequently if ALLOC_KSWAPD
> is lost, but this only happens when the 'retry:' loops is taken ?
Right, but see the comment:
/* Ensure kswapd doesn't accidentally go to sleep as long as we loop */
and that is not currently true. I think that was an inadvertent change.
Particularly since the changelog for 0a79cdad5eb2 says "No functional
change".
> >
> > Fixes: 0a79cdad5eb2 ("mm: use alloc_flags to record if kswapd can wake")
> > Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> > ---
> > mm/page_alloc.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index ba5c9402a5cb..4b97a03fa2dd 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -5147,7 +5147,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
> >
> > reserve_flags = __gfp_pfmemalloc_flags(gfp_mask);
> > if (reserve_flags)
> > - alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags);
> > + alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags) |
> > + (alloc_flags & ALLOC_KSWAPD);
> >
> > /*
> > * Reset the nodemask and zonelist iterators if memory policies can be
>
