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

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Message-ID: <631d62de-c9b5-3c5f-e0b3-df0109627a27@huaweicloud.com>
Date:   Tue, 15 Aug 2023 20:10:06 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        mgorman@...hsingularity.net, david@...hat.com
Subject: Re: [PATCH 7/9] mm/compaction: factor out code to test if we should
 run compaction for target order



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@...weicloud.com>
>> ---
>>   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.

>> +    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;
>>       }
>>         /*
> 
>