Re: [PATCH 7/9] mm/compaction: factor out code to test if we should run compaction for target order

[Baolin Wang]

On 8/22/2023 9:57 AM, Kemeng Shi wrote:
> on 8/19/2023 8:27 PM, Baolin Wang wrote:
> > On 8/15/2023 8:10 PM, Kemeng Shi wrote:
> > > on 8/15/2023 4:53 PM, Baolin Wang wrote:
> > > > On 8/5/2023 7:07 PM, Kemeng Shi wrote:
> > > > > We always do zone_watermark_ok check and compaction_suitable check
> > > > > together to test if compaction for target order should be runned.
> > > > > Factor these code out for preparation to remove repeat code.
> > > > >
> > > > > Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
> > > > > ---
> > > > >     mm/compaction.c | 42 +++++++++++++++++++++++++++++-------------
> > > > >     1 file changed, 29 insertions(+), 13 deletions(-)
> > > > >
> > > > > diff --git a/mm/compaction.c b/mm/compaction.c
> > > > > index b5a699ed526b..26787ebb0297 100644
> > > > > --- a/mm/compaction.c
> > > > > +++ b/mm/compaction.c
> > > > > @@ -2365,6 +2365,30 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
> > > > >         return false;
> > > > >     }
> > > > >     +/*
> > > > > + * Should we do compaction for target allocation order.
> > > > > + * Return COMPACT_SUCCESS if allocation for target order can be already
> > > > > + * satisfied
> > > > > + * Return COMPACT_SKIPPED if compaction for target order is likely to fail
> > > > > + * Return COMPACT_CONTINUE if compaction for target order should be runned
> > > > > + */
> > > > > +static inline enum compact_result
> > > > > +compaction_suit_allocation_order(struct zone *zone, unsigned int order,
> > > > > +                 int highest_zoneidx, unsigned int alloc_flags)
> > > > > +{
> > > > > +    unsigned long watermark;
> > > > > +
> > > > > +    watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
> > > >
> > > > IIUC, the watermark used in patch 8 and patch 9 is different, right? Have you measured the impact of modifying this watermark?
> > > Actually, there is no functional change intended. Consider wmark_pages with
> > > alloc_flags = 0 is equivalent to min_wmark_pages, patch 8 and patch 9 still
> > > use original watermark.
> >
> > Can you use ALLOC_WMARK_MIN macro to make it more clear?
> Sorry, I can't quite follow this. The watermark should differ with different
> alloc_flags instead of WMARK_MIN hard-coded.
> Patch 8 and patch 9 use watermark with WMARK_MIN as they get alloc_flags = 0.

I mean you can pass 'alloc_flags=ALLOC_WMARK_MIN' instead of a magic 
number 0 when calling compaction_suit_allocation_order() in patch 8 and 
patch 9.

> > And I think patch 8 and patch 9 should be squashed into patch 7 to convert all at once.
> Sure, i could do this in next version.
> > > > > +    if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
> > > > > +                  alloc_flags))
> > > > > +        return COMPACT_SUCCESS;
> > > > > +
> > > > > +    if (!compaction_suitable(zone, order, highest_zoneidx))
> > > > > +        return COMPACT_SKIPPED;
> > > > > +
> > > > > +    return COMPACT_CONTINUE;
> > > > > +}
> > > > > +
> > > > >     static enum compact_result
> > > > >     compact_zone(struct compact_control *cc, struct capture_control *capc)
> > > > >     {
> > > > > @@ -2390,19 +2414,11 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
> > > > >         cc->migratetype = gfp_migratetype(cc->gfp_mask);
> > > > >           if (compaction_with_allocation_order(cc->order)) {
> > > > > -        unsigned long watermark;
> > > > > -
> > > > > -        /* Allocation can already succeed, nothing to do */
> > > > > -        watermark = wmark_pages(cc->zone,
> > > > > -                    cc->alloc_flags & ALLOC_WMARK_MASK);
> > > > > -        if (zone_watermark_ok(cc->zone, cc->order, watermark,
> > > > > -                      cc->highest_zoneidx, cc->alloc_flags))
> > > > > -            return COMPACT_SUCCESS;
> > > > > -
> > > > > -        /* Compaction is likely to fail */
> > > > > -        if (!compaction_suitable(cc->zone, cc->order,
> > > > > -                     cc->highest_zoneidx))
> > > > > -            return COMPACT_SKIPPED;
> > > > > +        ret = compaction_suit_allocation_order(cc->zone, cc->order,
> > > > > +                               cc->highest_zoneidx,
> > > > > +                               cc->alloc_flags);
> > > > > +        if (ret != COMPACT_CONTINUE)
> > > > > +            return ret;
> > > > >         }
> > > > >           /*