| Message ID | 1734256867-19614-1-git-send-email-yangge1116@126.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [V4] mm, compaction: don't use ALLOC_CMA in long term GUP flow | expand |
On 2024/12/15 18:01, yangge1116@126.com wrote: > From: yangge <yangge1116@126.com> > > Since commit 984fdba6a32e ("mm, compaction: use proper alloc_flags > in __compaction_suitable()") allow compaction to proceed when free > pages required for compaction reside in the CMA pageblocks, it's > possible that __compaction_suitable() always returns true, and in > some cases, it's not acceptable. > > There are 4 NUMA nodes on my machine, and each NUMA node has 32GB > of memory. I have configured 16GB of CMA memory on each NUMA node, > and starting a 32GB virtual machine with device passthrough is > extremely slow, taking almost an hour. > > During the start-up of the virtual machine, it will call > pin_user_pages_remote(..., FOLL_LONGTERM, ...) to allocate memory. > Long term GUP cannot allocate memory from CMA area, so a maximum > of 16 GB of no-CMA memory on a NUMA node can be used as virtual > machine memory. Since there is 16G of free CMA memory on the NUMA > node, watermark for order-0 always be met for compaction, so > __compaction_suitable() always returns true, even if the node is > unable to allocate non-CMA memory for the virtual machine. > > For costly allocations, because __compaction_suitable() always > returns true, __alloc_pages_slowpath() can't exit at the appropriate > place, resulting in excessively long virtual machine startup times. > Call trace: > __alloc_pages_slowpath > if (compact_result == COMPACT_SKIPPED || > compact_result == COMPACT_DEFERRED) > goto nopage; // should exit __alloc_pages_slowpath() from here > > In order to quickly fall back to remote node, we should remove > ALLOC_CMA both in __compaction_suitable() and __isolate_free_page() > in long term GUP flow. After this fix, starting a 32GB virtual machine > with device passthrough takes only a few seconds. > > Fixes: 984fdba6a32e ("mm, compaction: use proper alloc_flags in __compaction_suitable()") > Cc: <stable@vger.kernel.org> > Signed-off-by: yangge <yangge1116@126.com> > --- > > V4: > - rich the commit log description > > V3: > - fix build errors > - add ALLOC_CMA both in should_continue_reclaim() and compaction_ready() > > V2: > - using the 'cc->alloc_flags' to determin if 'ALLOC_CMA' is needed > - rich the commit log description > > include/linux/compaction.h | 6 ++++-- > mm/compaction.c | 18 +++++++++++------- > mm/page_alloc.c | 4 +++- > mm/vmscan.c | 4 ++-- > 4 files changed, 20 insertions(+), 12 deletions(-) > > diff --git a/include/linux/compaction.h b/include/linux/compaction.h > index e947764..b4c3ac3 100644 > --- a/include/linux/compaction.h > +++ b/include/linux/compaction.h > @@ -90,7 +90,8 @@ extern enum compact_result try_to_compact_pages(gfp_t gfp_mask, > struct page **page); > extern void reset_isolation_suitable(pg_data_t *pgdat); > extern bool compaction_suitable(struct zone *zone, int order, > - int highest_zoneidx); > + int highest_zoneidx, > + unsigned int alloc_flags); > > extern void compaction_defer_reset(struct zone *zone, int order, > bool alloc_success); > @@ -108,7 +109,8 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat) > } > > static inline bool compaction_suitable(struct zone *zone, int order, > - int highest_zoneidx) > + int highest_zoneidx, > + unsigned int alloc_flags) > { > return false; > } > diff --git a/mm/compaction.c b/mm/compaction.c > index 07bd227..585f5ab 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -2381,9 +2381,11 @@ static enum compact_result compact_finished(struct compact_control *cc) > > static bool __compaction_suitable(struct zone *zone, int order, > int highest_zoneidx, > + unsigned int alloc_flags, > unsigned long wmark_target) > { > unsigned long watermark; > + bool use_cma; > /* > * Watermarks for order-0 must be met for compaction to be able to > * isolate free pages for migration targets. This means that the > @@ -2395,25 +2397,27 @@ static bool __compaction_suitable(struct zone *zone, int order, > * even if compaction succeeds. > * For costly orders, we require low watermark instead of min for > * compaction to proceed to increase its chances. > - * ALLOC_CMA is used, as pages in CMA pageblocks are considered > - * suitable migration targets > + * In addition to long term GUP flow, ALLOC_CMA is used, as pages in > + * CMA pageblocks are considered suitable migration targets > */ > watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? > low_wmark_pages(zone) : min_wmark_pages(zone); > watermark += compact_gap(order); > + use_cma = !!(alloc_flags & ALLOC_CMA); > return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx, > - ALLOC_CMA, wmark_target); > + use_cma ? ALLOC_CMA : 0, wmark_target); Why not just use 'alloc_flags & ALLOC_CMA' instead? then you can remove the 'use_cma' variable. > } > > /* > * compaction_suitable: Is this suitable to run compaction on this zone now? > */ > -bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx) > +bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx, > + unsigned int alloc_flags) > { > enum compact_result compact_result; > bool suitable; > > - suitable = __compaction_suitable(zone, order, highest_zoneidx, > + suitable = __compaction_suitable(zone, order, highest_zoneidx, alloc_flags, > zone_page_state(zone, NR_FREE_PAGES)); > /* > * fragmentation index determines if allocation failures are due to > @@ -2474,7 +2478,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, > available = zone_reclaimable_pages(zone) / order; > available += zone_page_state_snapshot(zone, NR_FREE_PAGES); > if (__compaction_suitable(zone, order, ac->highest_zoneidx, > - available)) > + alloc_flags, available)) > return true; > } > > @@ -2499,7 +2503,7 @@ compaction_suit_allocation_order(struct zone *zone, unsigned int order, > alloc_flags)) > return COMPACT_SUCCESS; > > - if (!compaction_suitable(zone, order, highest_zoneidx)) > + if (!compaction_suitable(zone, order, highest_zoneidx, alloc_flags)) > return COMPACT_SKIPPED; > > return COMPACT_CONTINUE; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index dde19db..9a5dfda 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2813,6 +2813,7 @@ int __isolate_free_page(struct page *page, unsigned int order) > { > struct zone *zone = page_zone(page); > int mt = get_pageblock_migratetype(page); > + bool pin; > > if (!is_migrate_isolate(mt)) { > unsigned long watermark; > @@ -2823,7 +2824,8 @@ int __isolate_free_page(struct page *page, unsigned int order) > * exists. > */ > watermark = zone->_watermark[WMARK_MIN] + (1UL << order); > - if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) > + pin = !!(current->flags & PF_MEMALLOC_PIN); > + if (!zone_watermark_ok(zone, 0, watermark, 0, pin ? 0 : ALLOC_CMA)) > return 0; I wonder why not pass ‘cc->alloc_flags’ as a parameter for __isolate_free_page()? > } > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 5e03a61..33f5b46 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -5815,7 +5815,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, > sc->reclaim_idx, 0)) > return false; > > - if (compaction_suitable(zone, sc->order, sc->reclaim_idx)) > + if (compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA)) > return false; > } > > @@ -6043,7 +6043,7 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) > return true; > > /* Compaction cannot yet proceed. Do reclaim. */ > - if (!compaction_suitable(zone, sc->order, sc->reclaim_idx)) > + if (!compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA)) > return false; > > /*
在 2024/12/16 16:41, Baolin Wang 写道: > > > On 2024/12/15 18:01, yangge1116@126.com wrote: >> From: yangge <yangge1116@126.com> >> >> Since commit 984fdba6a32e ("mm, compaction: use proper alloc_flags >> in __compaction_suitable()") allow compaction to proceed when free >> pages required for compaction reside in the CMA pageblocks, it's >> possible that __compaction_suitable() always returns true, and in >> some cases, it's not acceptable. >> >> There are 4 NUMA nodes on my machine, and each NUMA node has 32GB >> of memory. I have configured 16GB of CMA memory on each NUMA node, >> and starting a 32GB virtual machine with device passthrough is >> extremely slow, taking almost an hour. >> >> During the start-up of the virtual machine, it will call >> pin_user_pages_remote(..., FOLL_LONGTERM, ...) to allocate memory. >> Long term GUP cannot allocate memory from CMA area, so a maximum >> of 16 GB of no-CMA memory on a NUMA node can be used as virtual >> machine memory. Since there is 16G of free CMA memory on the NUMA >> node, watermark for order-0 always be met for compaction, so >> __compaction_suitable() always returns true, even if the node is >> unable to allocate non-CMA memory for the virtual machine. >> >> For costly allocations, because __compaction_suitable() always >> returns true, __alloc_pages_slowpath() can't exit at the appropriate >> place, resulting in excessively long virtual machine startup times. >> Call trace: >> __alloc_pages_slowpath >> if (compact_result == COMPACT_SKIPPED || >> compact_result == COMPACT_DEFERRED) >> goto nopage; // should exit __alloc_pages_slowpath() from here >> >> In order to quickly fall back to remote node, we should remove >> ALLOC_CMA both in __compaction_suitable() and __isolate_free_page() >> in long term GUP flow. After this fix, starting a 32GB virtual machine >> with device passthrough takes only a few seconds. >> >> Fixes: 984fdba6a32e ("mm, compaction: use proper alloc_flags in >> __compaction_suitable()") >> Cc: <stable@vger.kernel.org> >> Signed-off-by: yangge <yangge1116@126.com> >> --- >> >> V4: >> - rich the commit log description >> >> V3: >> - fix build errors >> - add ALLOC_CMA both in should_continue_reclaim() and compaction_ready() >> >> V2: >> - using the 'cc->alloc_flags' to determin if 'ALLOC_CMA' is needed >> - rich the commit log description >> >> include/linux/compaction.h | 6 ++++-- >> mm/compaction.c | 18 +++++++++++------- >> mm/page_alloc.c | 4 +++- >> mm/vmscan.c | 4 ++-- >> 4 files changed, 20 insertions(+), 12 deletions(-) >> >> diff --git a/include/linux/compaction.h b/include/linux/compaction.h >> index e947764..b4c3ac3 100644 >> --- a/include/linux/compaction.h >> +++ b/include/linux/compaction.h >> @@ -90,7 +90,8 @@ extern enum compact_result >> try_to_compact_pages(gfp_t gfp_mask, >> struct page **page); >> extern void reset_isolation_suitable(pg_data_t *pgdat); >> extern bool compaction_suitable(struct zone *zone, int order, >> - int highest_zoneidx); >> + int highest_zoneidx, >> + unsigned int alloc_flags); >> extern void compaction_defer_reset(struct zone *zone, int order, >> bool alloc_success); >> @@ -108,7 +109,8 @@ static inline void >> reset_isolation_suitable(pg_data_t *pgdat) >> } >> static inline bool compaction_suitable(struct zone *zone, int order, >> - int highest_zoneidx) >> + int highest_zoneidx, >> + unsigned int alloc_flags) >> { >> return false; >> } >> diff --git a/mm/compaction.c b/mm/compaction.c >> index 07bd227..585f5ab 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -2381,9 +2381,11 @@ static enum compact_result >> compact_finished(struct compact_control *cc) >> static bool __compaction_suitable(struct zone *zone, int order, >> int highest_zoneidx, >> + unsigned int alloc_flags, >> unsigned long wmark_target) >> { >> unsigned long watermark; >> + bool use_cma; >> /* >> * Watermarks for order-0 must be met for compaction to be able to >> * isolate free pages for migration targets. This means that the >> @@ -2395,25 +2397,27 @@ static bool __compaction_suitable(struct zone >> *zone, int order, >> * even if compaction succeeds. >> * For costly orders, we require low watermark instead of min for >> * compaction to proceed to increase its chances. >> - * ALLOC_CMA is used, as pages in CMA pageblocks are considered >> - * suitable migration targets >> + * In addition to long term GUP flow, ALLOC_CMA is used, as pages in >> + * CMA pageblocks are considered suitable migration targets >> */ >> watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? >> low_wmark_pages(zone) : min_wmark_pages(zone); >> watermark += compact_gap(order); >> + use_cma = !!(alloc_flags & ALLOC_CMA); >> return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx, >> - ALLOC_CMA, wmark_target); >> + use_cma ? ALLOC_CMA : 0, wmark_target); > > Why not just use 'alloc_flags & ALLOC_CMA' instead? then you can remove > the 'use_cma' variable. yes, I will change it in next version. > >> } >> /* >> * compaction_suitable: Is this suitable to run compaction on this >> zone now? >> */ >> -bool compaction_suitable(struct zone *zone, int order, int >> highest_zoneidx) >> +bool compaction_suitable(struct zone *zone, int order, int >> highest_zoneidx, >> + unsigned int alloc_flags) >> { >> enum compact_result compact_result; >> bool suitable; >> - suitable = __compaction_suitable(zone, order, highest_zoneidx, >> + suitable = __compaction_suitable(zone, order, highest_zoneidx, >> alloc_flags, >> zone_page_state(zone, NR_FREE_PAGES)); >> /* >> * fragmentation index determines if allocation failures are due to >> @@ -2474,7 +2478,7 @@ bool compaction_zonelist_suitable(struct >> alloc_context *ac, int order, >> available = zone_reclaimable_pages(zone) / order; >> available += zone_page_state_snapshot(zone, NR_FREE_PAGES); >> if (__compaction_suitable(zone, order, ac->highest_zoneidx, >> - available)) >> + alloc_flags, available)) >> return true; >> } >> @@ -2499,7 +2503,7 @@ compaction_suit_allocation_order(struct zone >> *zone, unsigned int order, >> alloc_flags)) >> return COMPACT_SUCCESS; >> - if (!compaction_suitable(zone, order, highest_zoneidx)) >> + if (!compaction_suitable(zone, order, highest_zoneidx, alloc_flags)) >> return COMPACT_SKIPPED; >> return COMPACT_CONTINUE; >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index dde19db..9a5dfda 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -2813,6 +2813,7 @@ int __isolate_free_page(struct page *page, >> unsigned int order) >> { >> struct zone *zone = page_zone(page); >> int mt = get_pageblock_migratetype(page); >> + bool pin; >> if (!is_migrate_isolate(mt)) { >> unsigned long watermark; >> @@ -2823,7 +2824,8 @@ int __isolate_free_page(struct page *page, >> unsigned int order) >> * exists. >> */ >> watermark = zone->_watermark[WMARK_MIN] + (1UL << order); >> - if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) >> + pin = !!(current->flags & PF_MEMALLOC_PIN); >> + if (!zone_watermark_ok(zone, 0, watermark, 0, pin ? 0 : >> ALLOC_CMA)) >> return 0; > > I wonder why not pass ‘cc->alloc_flags’ as a parameter for > __isolate_free_page()? Some places that use __isolate_free_page() don't have 'cc->alloc_flags', which leads me to believe that no modification is required. I will change it in next version. > >> } >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 5e03a61..33f5b46 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -5815,7 +5815,7 @@ static inline bool >> should_continue_reclaim(struct pglist_data *pgdat, >> sc->reclaim_idx, 0)) >> return false; >> - if (compaction_suitable(zone, sc->order, sc->reclaim_idx)) >> + if (compaction_suitable(zone, sc->order, sc->reclaim_idx, >> ALLOC_CMA)) >> return false; >> } >> @@ -6043,7 +6043,7 @@ static inline bool compaction_ready(struct zone >> *zone, struct scan_control *sc) >> return true; >> /* Compaction cannot yet proceed. Do reclaim. */ >> - if (!compaction_suitable(zone, sc->order, sc->reclaim_idx)) >> + if (!compaction_suitable(zone, sc->order, sc->reclaim_idx, >> ALLOC_CMA)) >> return false; >> /*
diff --git a/include/linux/compaction.h b/include/linux/compaction.h index e947764..b4c3ac3 100644 --- a/include/linux/compaction.h +++ b/include/linux/compaction.h @@ -90,7 +90,8 @@ extern enum compact_result try_to_compact_pages(gfp_t gfp_mask, struct page **page); extern void reset_isolation_suitable(pg_data_t *pgdat); extern bool compaction_suitable(struct zone *zone, int order, - int highest_zoneidx); + int highest_zoneidx, + unsigned int alloc_flags); extern void compaction_defer_reset(struct zone *zone, int order, bool alloc_success); @@ -108,7 +109,8 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat) } static inline bool compaction_suitable(struct zone *zone, int order, - int highest_zoneidx) + int highest_zoneidx, + unsigned int alloc_flags) { return false; } diff --git a/mm/compaction.c b/mm/compaction.c index 07bd227..585f5ab 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2381,9 +2381,11 @@ static enum compact_result compact_finished(struct compact_control *cc) static bool __compaction_suitable(struct zone *zone, int order, int highest_zoneidx, + unsigned int alloc_flags, unsigned long wmark_target) { unsigned long watermark; + bool use_cma; /* * Watermarks for order-0 must be met for compaction to be able to * isolate free pages for migration targets. This means that the @@ -2395,25 +2397,27 @@ static bool __compaction_suitable(struct zone *zone, int order, * even if compaction succeeds. * For costly orders, we require low watermark instead of min for * compaction to proceed to increase its chances. - * ALLOC_CMA is used, as pages in CMA pageblocks are considered - * suitable migration targets + * In addition to long term GUP flow, ALLOC_CMA is used, as pages in + * CMA pageblocks are considered suitable migration targets */ watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? low_wmark_pages(zone) : min_wmark_pages(zone); watermark += compact_gap(order); + use_cma = !!(alloc_flags & ALLOC_CMA); return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx, - ALLOC_CMA, wmark_target); + use_cma ? ALLOC_CMA : 0, wmark_target); } /* * compaction_suitable: Is this suitable to run compaction on this zone now? */ -bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx) +bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx, + unsigned int alloc_flags) { enum compact_result compact_result; bool suitable; - suitable = __compaction_suitable(zone, order, highest_zoneidx, + suitable = __compaction_suitable(zone, order, highest_zoneidx, alloc_flags, zone_page_state(zone, NR_FREE_PAGES)); /* * fragmentation index determines if allocation failures are due to @@ -2474,7 +2478,7 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order, available = zone_reclaimable_pages(zone) / order; available += zone_page_state_snapshot(zone, NR_FREE_PAGES); if (__compaction_suitable(zone, order, ac->highest_zoneidx, - available)) + alloc_flags, available)) return true; } @@ -2499,7 +2503,7 @@ compaction_suit_allocation_order(struct zone *zone, unsigned int order, alloc_flags)) return COMPACT_SUCCESS; - if (!compaction_suitable(zone, order, highest_zoneidx)) + if (!compaction_suitable(zone, order, highest_zoneidx, alloc_flags)) return COMPACT_SKIPPED; return COMPACT_CONTINUE; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index dde19db..9a5dfda 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2813,6 +2813,7 @@ int __isolate_free_page(struct page *page, unsigned int order) { struct zone *zone = page_zone(page); int mt = get_pageblock_migratetype(page); + bool pin; if (!is_migrate_isolate(mt)) { unsigned long watermark; @@ -2823,7 +2824,8 @@ int __isolate_free_page(struct page *page, unsigned int order) * exists. */ watermark = zone->_watermark[WMARK_MIN] + (1UL << order); - if (!zone_watermark_ok(zone, 0, watermark, 0, ALLOC_CMA)) + pin = !!(current->flags & PF_MEMALLOC_PIN); + if (!zone_watermark_ok(zone, 0, watermark, 0, pin ? 0 : ALLOC_CMA)) return 0; } diff --git a/mm/vmscan.c b/mm/vmscan.c index 5e03a61..33f5b46 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5815,7 +5815,7 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, sc->reclaim_idx, 0)) return false; - if (compaction_suitable(zone, sc->order, sc->reclaim_idx)) + if (compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA)) return false; } @@ -6043,7 +6043,7 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) return true; /* Compaction cannot yet proceed. Do reclaim. */ - if (!compaction_suitable(zone, sc->order, sc->reclaim_idx)) + if (!compaction_suitable(zone, sc->order, sc->reclaim_idx, ALLOC_CMA)) return false; /*