Currently, Mysql testcase show that a large number of thp are migrated from pmem node to toptier node, it will bring in more pgpromote_demoted and migrated failiure. because pmem node memory is marked as prot_none, it will be migrated by cpu access as soon as possible when it is hot, and it is unnesscessary to migrate thp to dram when dram memory is not enough, which will bring in more demoted and promoted. Hence, the patch forbid the thp to produce in pmem node. the result show about 3% improvements. the relative statistics is as follows. before appling patch: mysql prepare: pgpromote_demoted 908267 pgmigrate_fail_dst_node_fail 428223 pgmigrate_fail_numa_isolate_fail 460480 mysql run: pgpromote_demoted 2901105 pgmigrate_fail_dst_node_fail 5653776 pgmigrate_fail_numa_isolate_fail 5686052 after appling patch: mysql prepare: pgpromote_demoted 839297 pgmigrate_fail_dst_node_fail 36585 pgmigrate_fail_numa_isolate_fail 36585 mysql run: pgpromote_demoted 913828 pgmigrate_fail_dst_node_fail 235863 pgmigrate_fail_numa_isolate_fail 235870 Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> --- mm/page_alloc.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8cfce92..4fff3cd 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); } +static inline bool allow_hugepage_allocation(int nid, unsigned int order) +{ + if (node_is_toptier(nid)) + return true; + + if (order != HPAGE_PMD_ORDER) + return true; + + return false; +} + /** * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages * @page: The page within the block of interest @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) } } + if (!allow_hugepage_allocation(zone_to_nid(zone), order)) + continue; +

zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> writes: > Currently, Mysql testcase show that a large number of thp are migrated > from pmem node to toptier node, it will bring in more pgpromote_demoted > and migrated failiure. because pmem node memory is marked as prot_none, > it will be migrated by cpu access as soon as possible when it is hot, > and it is unnesscessary to migrate thp to dram when dram memory is not > enough, which will bring in more demoted and promoted. > > Hence, the patch forbid the thp to produce in pmem node. the result show > about 3% improvements. the relative statistics is as follows. > > before appling patch: > mysql prepare: > pgpromote_demoted 908267 > pgmigrate_fail_dst_node_fail 428223 > pgmigrate_fail_numa_isolate_fail 460480 > > mysql run: > pgpromote_demoted 2901105 > pgmigrate_fail_dst_node_fail 5653776 > pgmigrate_fail_numa_isolate_fail 5686052 > > after appling patch: > mysql prepare: > pgpromote_demoted 839297 > pgmigrate_fail_dst_node_fail 36585 > pgmigrate_fail_numa_isolate_fail 36585 > > mysql run: > pgpromote_demoted 913828 > pgmigrate_fail_dst_node_fail 235863 > pgmigrate_fail_numa_isolate_fail 235870 > > Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> > --- > mm/page_alloc.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 8cfce92..4fff3cd 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned > return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); > } > +static inline bool allow_hugepage_allocation(int nid, unsigned > int order) > +{ > + if (node_is_toptier(nid)) > + return true; > + > + if (order != HPAGE_PMD_ORDER) > + return true; > + > + return false; > +} > + > /** > * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages > * @page: The page within the block of interest > @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) > } > } > + if (!allow_hugepage_allocation(zone_to_nid(zone), > order)) > + continue; > + It appears that this will disable node reclaiming for THP allocation. So more pages will be allocated in PMEM node because of allocation fallback?

zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: > On 2022/2/10 8:58 H, Huang, Ying wrote: >> zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> writes: >> >>> Currently, Mysql testcase show that a large number of thp are migrated >>> from pmem node to toptier node, it will bring in more pgpromote_demoted >>> and migrated failiure. because pmem node memory is marked as prot_none, >>> it will be migrated by cpu access as soon as possible when it is hot, >>> and it is unnesscessary to migrate thp to dram when dram memory is not >>> enough, which will bring in more demoted and promoted. >>> >>> Hence, the patch forbid the thp to produce in pmem node. the result show >>> about 3% improvements. the relative statistics is as follows. >>> >>> before appling patch: >>> mysql prepare: >>> pgpromote_demoted 908267 >>> pgmigrate_fail_dst_node_fail 428223 >>> pgmigrate_fail_numa_isolate_fail 460480 >>> >>> mysql run: >>> pgpromote_demoted 2901105 >>> pgmigrate_fail_dst_node_fail 5653776 >>> pgmigrate_fail_numa_isolate_fail 5686052 >>> >>> after appling patch: >>> mysql prepare: >>> pgpromote_demoted 839297 >>> pgmigrate_fail_dst_node_fail 36585 >>> pgmigrate_fail_numa_isolate_fail 36585 >>> >>> mysql run: >>> pgpromote_demoted 913828 >>> pgmigrate_fail_dst_node_fail 235863 >>> pgmigrate_fail_numa_isolate_fail 235870 >>> >>> Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> >>> --- >>> mm/page_alloc.c | 14 ++++++++++++++ >>> 1 file changed, 14 insertions(+) >>> >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index 8cfce92..4fff3cd 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned >>> return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); >>> } >>> +static inline bool allow_hugepage_allocation(int nid, unsigned >>> int order) >>> +{ >>> + if (node_is_toptier(nid)) >>> + return true; >>> + >>> + if (order != HPAGE_PMD_ORDER) >>> + return true; >>> + >>> + return false; >>> +} >>> + >>> /** >>> * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages >>> * @page: The page within the block of interest >>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>> } >>> } >>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>> order)) >>> + continue; >>> + >> It appears that this will disable node reclaiming for THP allocation. >> So more pages will be allocated in PMEM node because of allocation >> fallback? > We just allow normal pages allocate in pmem node, hence, thp > allocation will fallback to produce more normal pages. > > Mysql testcase show that too many thps is promoted to toptier , > due to toptier memory is not enough, it will bring in > > more pgpromote_deomted and dst_node_full counter increasing. In > that case, we prefer to remote access rather > > than migrate thp between pmem and toptier node frequently, which > will make performance decrease. Maybe we are looking at different source code :-). In latest upstream code, zone_allows_reclaim() is to control node reclaiming (or zone reclaim) only. Which repo should I look?

> zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: > >> On 2022/2/10 8:58 H, Huang, Ying wrote: >>> zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> writes: >>> >>>> Currently, Mysql testcase show that a large number of thp are migrated >>>> from pmem node to toptier node, it will bring in more pgpromote_demoted >>>> and migrated failiure. because pmem node memory is marked as prot_none, >>>> it will be migrated by cpu access as soon as possible when it is hot, >>>> and it is unnesscessary to migrate thp to dram when dram memory is not >>>> enough, which will bring in more demoted and promoted. >>>> >>>> Hence, the patch forbid the thp to produce in pmem node. the result show >>>> about 3% improvements. the relative statistics is as follows. >>>> >>>> before appling patch: >>>> mysql prepare: >>>> pgpromote_demoted 908267 >>>> pgmigrate_fail_dst_node_fail 428223 >>>> pgmigrate_fail_numa_isolate_fail 460480 >>>> >>>> mysql run: >>>> pgpromote_demoted 2901105 >>>> pgmigrate_fail_dst_node_fail 5653776 >>>> pgmigrate_fail_numa_isolate_fail 5686052 >>>> >>>> after appling patch: >>>> mysql prepare: >>>> pgpromote_demoted 839297 >>>> pgmigrate_fail_dst_node_fail 36585 >>>> pgmigrate_fail_numa_isolate_fail 36585 >>>> >>>> mysql run: >>>> pgpromote_demoted 913828 >>>> pgmigrate_fail_dst_node_fail 235863 >>>> pgmigrate_fail_numa_isolate_fail 235870 >>>> >>>> Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> >>>> --- >>>> mm/page_alloc.c | 14 ++++++++++++++ >>>> 1 file changed, 14 insertions(+) >>>> >>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>> index 8cfce92..4fff3cd 100644 >>>> --- a/mm/page_alloc.c >>>> +++ b/mm/page_alloc.c >>>> @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned >>>> return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); >>>> } >>>> +static inline bool allow_hugepage_allocation(int nid, unsigned >>>> int order) >>>> +{ >>>> + if (node_is_toptier(nid)) >>>> + return true; >>>> + >>>> + if (order != HPAGE_PMD_ORDER) >>>> + return true; >>>> + >>>> + return false; >>>> +} >>>> + >>>> /** >>>> * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages >>>> * @page: The page within the block of interest >>>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>>> } >>>> } >>>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>>> order)) >>>> + continue; >>>> + >>> It appears that this will disable node reclaiming for THP allocation. >>> So more pages will be allocated in PMEM node because of allocation >>> fallback? >> We just allow normal pages allocate in pmem node, hence, thp >> allocation will fallback to produce more normal pages. >> >> Mysql testcase show that too many thps is promoted to toptier , >> due to toptier memory is not enough, it will bring in >> >> more pgpromote_deomted and dst_node_full counter increasing. In >> that case, we prefer to remote access rather >> >> than migrate thp between pmem and toptier node frequently, which >> will make performance decrease. > Maybe we are looking at different source code :-). In latest > upstream > code, zone_allows_reclaim() is to control node reclaiming (or zone > reclaim) only. Which repo should I look? I think you misunderstood the change, the change is in get_page_from_freelist(), not in zone_allows_reclaim().

From my understanding, Zhongjiang is trying to disable the memory allocation fallback for THP, right?

But that will cause more demotion if we can not fallback to PMEM node?

On 2022/2/10 3:03 H, Huang, Ying wrote: > Baolin Wang <baolin.wang(a)linux.alibaba.com> writes: > >>> zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: >>> >>>> On 2022/2/10 8:58 H, Huang, Ying wrote: >>>>> zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> writes: >>>>> >>>>>> Currently, Mysql testcase show that a large number of thp are migrated >>>>>> from pmem node to toptier node, it will bring in more pgpromote_demoted >>>>>> and migrated failiure. because pmem node memory is marked as prot_none, >>>>>> it will be migrated by cpu access as soon as possible when it is hot, >>>>>> and it is unnesscessary to migrate thp to dram when dram memory is not >>>>>> enough, which will bring in more demoted and promoted. >>>>>> >>>>>> Hence, the patch forbid the thp to produce in pmem node. the result show >>>>>> about 3% improvements. the relative statistics is as follows. >>>>>> >>>>>> before appling patch: >>>>>> mysql prepare: >>>>>> pgpromote_demoted 908267 >>>>>> pgmigrate_fail_dst_node_fail 428223 >>>>>> pgmigrate_fail_numa_isolate_fail 460480 >>>>>> >>>>>> mysql run: >>>>>> pgpromote_demoted 2901105 >>>>>> pgmigrate_fail_dst_node_fail 5653776 >>>>>> pgmigrate_fail_numa_isolate_fail 5686052 >>>>>> >>>>>> after appling patch: >>>>>> mysql prepare: >>>>>> pgpromote_demoted 839297 >>>>>> pgmigrate_fail_dst_node_fail 36585 >>>>>> pgmigrate_fail_numa_isolate_fail 36585 >>>>>> >>>>>> mysql run: >>>>>> pgpromote_demoted 913828 >>>>>> pgmigrate_fail_dst_node_fail 235863 >>>>>> pgmigrate_fail_numa_isolate_fail 235870 >>>>>> >>>>>> Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> >>>>>> --- >>>>>> mm/page_alloc.c | 14 ++++++++++++++ >>>>>> 1 file changed, 14 insertions(+) >>>>>> >>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>>>> index 8cfce92..4fff3cd 100644 >>>>>> --- a/mm/page_alloc.c >>>>>> +++ b/mm/page_alloc.c >>>>>> @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned >>>>>> return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); >>>>>> } >>>>>> +static inline bool allow_hugepage_allocation(int nid, unsigned >>>>>> int order) >>>>>> +{ >>>>>> + if (node_is_toptier(nid)) >>>>>> + return true; >>>>>> + >>>>>> + if (order != HPAGE_PMD_ORDER) >>>>>> + return true; >>>>>> + >>>>>> + return false; >>>>>> +} >>>>>> + >>>>>> /** >>>>>> * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages >>>>>> * @page: The page within the block of interest >>>>>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>>>>> } >>>>>> } >>>>>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>>>>> order)) >>>>>> + continue; >>>>>> + >>>>> It appears that this will disable node reclaiming for THP allocation. >>>>> So more pages will be allocated in PMEM node because of allocation >>>>> fallback? >>>> We just allow normal pages allocate in pmem node, hence, thp >>>> allocation will fallback to produce more normal pages. >>>> >>>> Mysql testcase show that too many thps is promoted to toptier , >>>> due to toptier memory is not enough, it will bring in >>>> >>>> more pgpromote_deomted and dst_node_full counter increasing. In >>>> that case, we prefer to remote access rather >>>> >>>> than migrate thp between pmem and toptier node frequently, which >>>> will make performance decrease. >>> Maybe we are looking at different source code :-). In latest >>> upstream >>> code, zone_allows_reclaim() is to control node reclaiming (or zone >>> reclaim) only. Which repo should I look? >> I think you misunderstood the change, the change is in >> get_page_from_freelist(), not in zone_allows_reclaim(). > OK, I see. I think the `diff` program fools me: > > @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) > } > } > + if (!allow_hugepage_allocation(zone_to_nid(zone), > order)) > + continue; > + > if (no_fallback && nr_online_nodes > 1 && > zone != ac->preferred_zoneref->zone) { > int local_nid; > > >> From my understanding, Zhongjiang is trying to disable the memory >> allocation fallback for THP, right? > I think so too now. > >> But that will cause more demotion if we can not fallback to PMEM node? > If THP fails to be allocated, normal pages will be allocated instead. > And it appears that if THP is failed to be demoted (with this patch, it > will always fail), THP will be split too. So we may have much less THP > in system with the patch. Zhongjiang, Can you check it? The patch aims to prevent thp allocation in pmem node, I has checked that there are not an thp is created in pmem node which is intended. Dram node still has a lot of thp and can be collapsed. > Another choice is to split THP if migration fails. That's always a > question to prefer THP or local/hot normal pages. Test performance will decrease if a large number of thp in pmem node, promotion will fail more frequently relative to normal page allocation because dram memory is not enough to result in waking up kswapd. hence the influence is too much promotion failure and pgpromote_demoted. And Maybe thp is not really needed for testcase, but an subpage of thp.

On 2022/2/11 7:58 H, Huang, Ying wrote: > zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: > >> On 2022/2/10 3:03 H, Huang, Ying wrote: >>> Baolin Wang <baolin.wang(a)linux.alibaba.com> writes: >>> >>>>> zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: >>>>> >>>>>> On 2022/2/10 8:58 H, Huang, Ying wrote: >>>>>>> zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> writes: >>>>>>> >>>>>>>> Currently, Mysql testcase show that a large number of thp are migrated >>>>>>>> from pmem node to toptier node, it will bring in more pgpromote_demoted >>>>>>>> and migrated failiure. because pmem node memory is marked as prot_none, >>>>>>>> it will be migrated by cpu access as soon as possible when it is hot, >>>>>>>> and it is unnesscessary to migrate thp to dram when dram memory is not >>>>>>>> enough, which will bring in more demoted and promoted. >>>>>>>> >>>>>>>> Hence, the patch forbid the thp to produce in pmem node. the result show >>>>>>>> about 3% improvements. the relative statistics is as follows. >>>>>>>> >>>>>>>> before appling patch: >>>>>>>> mysql prepare: >>>>>>>> pgpromote_demoted 908267 >>>>>>>> pgmigrate_fail_dst_node_fail 428223 >>>>>>>> pgmigrate_fail_numa_isolate_fail 460480 >>>>>>>> >>>>>>>> mysql run: >>>>>>>> pgpromote_demoted 2901105 >>>>>>>> pgmigrate_fail_dst_node_fail 5653776 >>>>>>>> pgmigrate_fail_numa_isolate_fail 5686052 >>>>>>>> >>>>>>>> after appling patch: >>>>>>>> mysql prepare: >>>>>>>> pgpromote_demoted 839297 >>>>>>>> pgmigrate_fail_dst_node_fail 36585 >>>>>>>> pgmigrate_fail_numa_isolate_fail 36585 >>>>>>>> >>>>>>>> mysql run: >>>>>>>> pgpromote_demoted 913828 >>>>>>>> pgmigrate_fail_dst_node_fail 235863 >>>>>>>> pgmigrate_fail_numa_isolate_fail 235870 >>>>>>>> >>>>>>>> Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> >>>>>>>> --- >>>>>>>> mm/page_alloc.c | 14 ++++++++++++++ >>>>>>>> 1 file changed, 14 insertions(+) >>>>>>>> >>>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>>>>>> index 8cfce92..4fff3cd 100644 >>>>>>>> --- a/mm/page_alloc.c >>>>>>>> +++ b/mm/page_alloc.c >>>>>>>> @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned >>>>>>>> return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); >>>>>>>> } >>>>>>>> +static inline bool allow_hugepage_allocation(int nid, unsigned >>>>>>>> int order) >>>>>>>> +{ >>>>>>>> + if (node_is_toptier(nid)) >>>>>>>> + return true; >>>>>>>> + >>>>>>>> + if (order != HPAGE_PMD_ORDER) >>>>>>>> + return true; >>>>>>>> + >>>>>>>> + return false; >>>>>>>> +} >>>>>>>> + >>>>>>>> /** >>>>>>>> * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages >>>>>>>> * @page: The page within the block of interest >>>>>>>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>>>>>>> } >>>>>>>> } >>>>>>>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>>>>>>> order)) >>>>>>>> + continue; >>>>>>>> + >>>>>>> It appears that this will disable node reclaiming for THP allocation. >>>>>>> So more pages will be allocated in PMEM node because of allocation >>>>>>> fallback? >>>>>> We just allow normal pages allocate in pmem node, hence, thp >>>>>> allocation will fallback to produce more normal pages. >>>>>> >>>>>> Mysql testcase show that too many thps is promoted to toptier , >>>>>> due to toptier memory is not enough, it will bring in >>>>>> >>>>>> more pgpromote_deomted and dst_node_full counter increasing. In >>>>>> that case, we prefer to remote access rather >>>>>> >>>>>> than migrate thp between pmem and toptier node frequently, which >>>>>> will make performance decrease. >>>>> Maybe we are looking at different source code :-). In latest >>>>> upstream >>>>> code, zone_allows_reclaim() is to control node reclaiming (or zone >>>>> reclaim) only. Which repo should I look? >>>> I think you misunderstood the change, the change is in >>>> get_page_from_freelist(), not in zone_allows_reclaim(). >>> OK, I see. I think the `diff` program fools me: >>> >>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>> } >>> } >>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>> order)) >>> + continue; >>> + >>> if (no_fallback && nr_online_nodes > 1 && >>> zone != ac->preferred_zoneref->zone) { >>> int local_nid; >>> >>> >>>> From my understanding, Zhongjiang is trying to disable the memory >>>> allocation fallback for THP, right? >>> I think so too now. >>> >>>> But that will cause more demotion if we can not fallback to PMEM node? >>> If THP fails to be allocated, normal pages will be allocated instead. >>> And it appears that if THP is failed to be demoted (with this patch, it >>> will always fail), THP will be split too. So we may have much less THP >>> in system with the patch. Zhongjiang, Can you check it? >> The patch aims to prevent thp allocation in pmem node, I has >> checked that there are not an thp is created >> >> in pmem node which is intended. Dram node still has a lot of >> thp and can be collapsed. >> >>> Another choice is to split THP if migration fails. That's always a >>> question to prefer THP or local/hot normal pages. >> Test performance will decrease if a large number of thp in pmem >> node, promotion will fail more frequently >> >> relative to normal page allocation because dram memory is not enough >> to result in waking up kswapd. >> >> >> hence the influence is too much promotion failure and >> pgpromote_demoted. And Maybe thp is not >> >> really needed for testcase, but an subpage of thp. > Yes. So I suggest to try to fallback to split THP upon THP allocation > failure on DRAM. Just disable nosplit logic in migrate_pages(). The upstream do as you said. It will fallback to split thp into normal page when promotion fail to allocation thp on dram.

On 2022/2/11 6:52 H, Huang, Ying wrote: > zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: > >> On 2022/2/11 7:58 H, Huang, Ying wrote: >>> zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: >>> >>>> On 2022/2/10 3:03 H, Huang, Ying wrote: >>>>> Baolin Wang <baolin.wang(a)linux.alibaba.com> writes: >>>>> >>>>>>> zhong jiang <zhongjiang-ali(a)linux.alibaba.com> writes: >>>>>>> >>>>>>>> On 2022/2/10 8:58 H, Huang, Ying wrote: >>>>>>>>> zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> writes: >>>>>>>>> >>>>>>>>>> Currently, Mysql testcase show that a large number of thp are migrated >>>>>>>>>> from pmem node to toptier node, it will bring in more pgpromote_demoted >>>>>>>>>> and migrated failiure. because pmem node memory is marked as prot_none, >>>>>>>>>> it will be migrated by cpu access as soon as possible when it is hot, >>>>>>>>>> and it is unnesscessary to migrate thp to dram when dram memory is not >>>>>>>>>> enough, which will bring in more demoted and promoted. >>>>>>>>>> >>>>>>>>>> Hence, the patch forbid the thp to produce in pmem node. the result show >>>>>>>>>> about 3% improvements. the relative statistics is as follows. >>>>>>>>>> >>>>>>>>>> before appling patch: >>>>>>>>>> mysql prepare: >>>>>>>>>> pgpromote_demoted 908267 >>>>>>>>>> pgmigrate_fail_dst_node_fail 428223 >>>>>>>>>> pgmigrate_fail_numa_isolate_fail 460480 >>>>>>>>>> >>>>>>>>>> mysql run: >>>>>>>>>> pgpromote_demoted 2901105 >>>>>>>>>> pgmigrate_fail_dst_node_fail 5653776 >>>>>>>>>> pgmigrate_fail_numa_isolate_fail 5686052 >>>>>>>>>> >>>>>>>>>> after appling patch: >>>>>>>>>> mysql prepare: >>>>>>>>>> pgpromote_demoted 839297 >>>>>>>>>> pgmigrate_fail_dst_node_fail 36585 >>>>>>>>>> pgmigrate_fail_numa_isolate_fail 36585 >>>>>>>>>> >>>>>>>>>> mysql run: >>>>>>>>>> pgpromote_demoted 913828 >>>>>>>>>> pgmigrate_fail_dst_node_fail 235863 >>>>>>>>>> pgmigrate_fail_numa_isolate_fail 235870 >>>>>>>>>> >>>>>>>>>> Signed-off-by: zhongjiang-ali <zhongjiang-ali(a)linux.alibaba.com> >>>>>>>>>> --- >>>>>>>>>> mm/page_alloc.c | 14 ++++++++++++++ >>>>>>>>>> 1 file changed, 14 insertions(+) >>>>>>>>>> >>>>>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>>>>>>>>> index 8cfce92..4fff3cd 100644 >>>>>>>>>> --- a/mm/page_alloc.c >>>>>>>>>> +++ b/mm/page_alloc.c >>>>>>>>>> @@ -461,6 +461,17 @@ static __always_inline int get_pfnblock_migratetype(struct page *page, unsigned >>>>>>>>>> return __get_pfnblock_flags_mask(page, pfn, PB_migrate_end, MIGRATETYPE_MASK); >>>>>>>>>> } >>>>>>>>>> +static inline bool allow_hugepage_allocation(int nid, unsigned >>>>>>>>>> int order) >>>>>>>>>> +{ >>>>>>>>>> + if (node_is_toptier(nid)) >>>>>>>>>> + return true; >>>>>>>>>> + >>>>>>>>>> + if (order != HPAGE_PMD_ORDER) >>>>>>>>>> + return true; >>>>>>>>>> + >>>>>>>>>> + return false; >>>>>>>>>> +} >>>>>>>>>> + >>>>>>>>>> /** >>>>>>>>>> * set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages >>>>>>>>>> * @page: The page within the block of interest >>>>>>>>>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>>>>>>>>> } >>>>>>>>>> } >>>>>>>>>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>>>>>>>>> order)) >>>>>>>>>> + continue; >>>>>>>>>> + >>>>>>>>> It appears that this will disable node reclaiming for THP allocation. >>>>>>>>> So more pages will be allocated in PMEM node because of allocation >>>>>>>>> fallback? >>>>>>>> We just allow normal pages allocate in pmem node, hence, thp >>>>>>>> allocation will fallback to produce more normal pages. >>>>>>>> >>>>>>>> Mysql testcase show that too many thps is promoted to toptier , >>>>>>>> due to toptier memory is not enough, it will bring in >>>>>>>> >>>>>>>> more pgpromote_deomted and dst_node_full counter increasing. In >>>>>>>> that case, we prefer to remote access rather >>>>>>>> >>>>>>>> than migrate thp between pmem and toptier node frequently, which >>>>>>>> will make performance decrease. >>>>>>> Maybe we are looking at different source code :-). In latest >>>>>>> upstream >>>>>>> code, zone_allows_reclaim() is to control node reclaiming (or zone >>>>>>> reclaim) only. Which repo should I look? >>>>>> I think you misunderstood the change, the change is in >>>>>> get_page_from_freelist(), not in zone_allows_reclaim(). >>>>> OK, I see. I think the `diff` program fools me: >>>>> >>>>> @@ -3689,6 +3700,9 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >>>>> } >>>>> } >>>>> + if (!allow_hugepage_allocation(zone_to_nid(zone), >>>>> order)) >>>>> + continue; >>>>> + >>>>> if (no_fallback && nr_online_nodes > 1 && >>>>> zone != ac->preferred_zoneref->zone) { >>>>> int local_nid; >>>>> >>>>> >>>>>> From my understanding, Zhongjiang is trying to disable the memory >>>>>> allocation fallback for THP, right? >>>>> I think so too now. >>>>> >>>>>> But that will cause more demotion if we can not fallback to PMEM node? >>>>> If THP fails to be allocated, normal pages will be allocated instead. >>>>> And it appears that if THP is failed to be demoted (with this patch, it >>>>> will always fail), THP will be split too. So we may have much less THP >>>>> in system with the patch. Zhongjiang, Can you check it? >>>> The patch aims to prevent thp allocation in pmem node, I has >>>> checked that there are not an thp is created >>>> >>>> in pmem node which is intended. Dram node still has a lot of >>>> thp and can be collapsed. >>>> >>>>> Another choice is to split THP if migration fails. That's always a >>>>> question to prefer THP or local/hot normal pages. >>>> Test performance will decrease if a large number of thp in pmem >>>> node, promotion will fail more frequently >>>> >>>> relative to normal page allocation because dram memory is not enough >>>> to result in waking up kswapd. >>>> >>>> >>>> hence the influence is too much promotion failure and >>>> pgpromote_demoted. And Maybe thp is not >>>> >>>> really needed for testcase, but an subpage of thp. >>> Yes. So I suggest to try to fallback to split THP upon THP allocation >>> failure on DRAM. Just disable nosplit logic in migrate_pages(). >> The upstream do as you said. It will fallback to split thp >> into normal page when promotion fail to allocation >> >> thp on dram. > Not for NUMA balancing. Because > > bool nosplit = (reason == MR_NUMA_MISPLACED); Maybe you has misunderstanded the patch aiming to solve the problem. The current issue is too many thps in pmem node and dram node is not enough, as mysql benchmark test,

promote thp will be likely failure because of failed to allocation memory in dram. and in the situation, promote normal page is more suitable, but it is too late to fallback to split thp.