From: Johannes Weiner <hannes@cmpxchg.org> mainline inclusion from mainline-v6.10-rc1 commit 17edeb5d3f761c20fd28f6002f5a9faa53c0a0d8 category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/IBC4T0 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Patch series "mm: page_alloc: freelist migratetype hygiene", v4. The page allocator's mobility grouping is intended to keep unmovable pages separate from reclaimable/compactable ones to allow on-demand defragmentation for higher-order allocations and huge pages. Currently, there are several places where accidental type mixing occurs: an allocation asks for a page of a certain migratetype and receives another. This ruins pageblocks for compaction, which in turn makes allocating huge pages more expensive and less reliable. The series addresses those causes. The last patch adds type checks on all freelist movements to prevent new violations being introduced. The benefits can be seen in a mixed workload that stresses the machine with a memcache-type workload and a kernel build job while periodically attempting to allocate batches of THP. The following data is aggregated over 50 consecutive defconfig builds: VANILLA PATCHED Hugealloc Time mean 165843.93 ( +0.00%) 113025.88 ( -31.85%) Hugealloc Time stddev 158957.35 ( +0.00%) 114716.07 ( -27.83%) Kbuild Real time 310.24 ( +0.00%) 300.73 ( -3.06%) Kbuild User time 1271.13 ( +0.00%) 1259.42 ( -0.92%) Kbuild System time 582.02 ( +0.00%) 559.79 ( -3.81%) THP fault alloc 30585.14 ( +0.00%) 40853.62 ( +33.57%) THP fault fallback 36626.46 ( +0.00%) 26357.62 ( -28.04%) THP fault fail rate % 54.49 ( +0.00%) 39.22 ( -27.53%) Pagealloc fallback 1328.00 ( +0.00%) 1.00 ( -99.85%) Pagealloc type mismatch 181009.50 ( +0.00%) 0.00 ( -100.00%) Direct compact stall 434.56 ( +0.00%) 257.66 ( -40.61%) Direct compact fail 421.70 ( +0.00%) 249.94 ( -40.63%) Direct compact success 12.86 ( +0.00%) 7.72 ( -37.09%) Direct compact success rate % 2.86 ( +0.00%) 2.82 ( -0.96%) Compact daemon scanned migrate 3370059.62 ( +0.00%) 3612054.76 ( +7.18%) Compact daemon scanned free 7718439.20 ( +0.00%) 5386385.02 ( -30.21%) Compact direct scanned migrate 309248.62 ( +0.00%) 176721.04 ( -42.85%) Compact direct scanned free 433582.84 ( +0.00%) 315727.66 ( -27.18%) Compact migrate scanned daemon % 91.20 ( +0.00%) 94.48 ( +3.56%) Compact free scanned daemon % 94.58 ( +0.00%) 94.42 ( -0.16%) Compact total migrate scanned 3679308.24 ( +0.00%) 3788775.80 ( +2.98%) Compact total free scanned 8152022.04 ( +0.00%) 5702112.68 ( -30.05%) Alloc stall 872.04 ( +0.00%) 5156.12 ( +490.71%) Pages kswapd scanned 510645.86 ( +0.00%) 3394.94 ( -99.33%) Pages kswapd reclaimed 134811.62 ( +0.00%) 2701.26 ( -98.00%) Pages direct scanned 99546.06 ( +0.00%) 376407.52 ( +278.12%) Pages direct reclaimed 62123.40 ( +0.00%) 289535.70 ( +366.06%) Pages total scanned 610191.92 ( +0.00%) 379802.46 ( -37.76%) Pages scanned kswapd % 76.36 ( +0.00%) 0.10 ( -98.58%) Swap out 12057.54 ( +0.00%) 15022.98 ( +24.59%) Swap in 209.16 ( +0.00%) 256.48 ( +22.52%) File refaults 17701.64 ( +0.00%) 11765.40 ( -33.53%) Huge page success rate is higher, allocation latencies are shorter and more predictable. Stealing (fallback) rate is drastically reduced. Notably, while the vanilla kernel keeps doing fallbacks on an ongoing basis, the patched kernel enters a steady state once the distribution of block types is adequate for the workload. Steals over 50 runs: VANILLA PATCHED 1504.0 227.0 1557.0 6.0 1391.0 13.0 1080.0 26.0 1057.0 40.0 1156.0 6.0 805.0 46.0 736.0 20.0 1747.0 2.0 1699.0 34.0 1269.0 13.0 1858.0 12.0 907.0 4.0 727.0 2.0 563.0 2.0 3094.0 2.0 10211.0 3.0 2621.0 1.0 5508.0 2.0 1060.0 2.0 538.0 3.0 5773.0 2.0 2199.0 0.0 3781.0 2.0 1387.0 1.0 4977.0 0.0 2865.0 1.0 1814.0 1.0 3739.0 1.0 6857.0 0.0 382.0 0.0 407.0 1.0 3784.0 0.0 297.0 0.0 298.0 0.0 6636.0 0.0 4188.0 0.0 242.0 0.0 9960.0 0.0 5816.0 0.0 354.0 0.0 287.0 0.0 261.0 0.0 140.0 1.0 2065.0 0.0 312.0 0.0 331.0 0.0 164.0 0.0 465.0 1.0 219.0 0.0 Type mismatches are down too. Those count every time an allocation request asks for one migratetype and gets another. This can still occur minimally in the patched kernel due to non-stealing fallbacks, but it's quite rare and follows the pattern of overall fallbacks - once the block type distribution settles, mismatches cease as well: VANILLA: PATCHED: 182602.0 268.0 135794.0 20.0 88619.0 19.0 95973.0 0.0 129590.0 0.0 129298.0 0.0 147134.0 0.0 230854.0 0.0 239709.0 0.0 137670.0 0.0 132430.0 0.0 65712.0 0.0 57901.0 0.0 67506.0 0.0 63565.0 4.0 34806.0 0.0 42962.0 0.0 32406.0 0.0 38668.0 0.0 61356.0 0.0 57800.0 0.0 41435.0 0.0 83456.0 0.0 65048.0 0.0 28955.0 0.0 47597.0 0.0 75117.0 0.0 55564.0 0.0 38280.0 0.0 52404.0 0.0 26264.0 0.0 37538.0 0.0 19671.0 0.0 30936.0 0.0 26933.0 0.0 16962.0 0.0 44554.0 0.0 46352.0 0.0 24995.0 0.0 35152.0 0.0 12823.0 0.0 21583.0 0.0 18129.0 0.0 31693.0 0.0 28745.0 0.0 33308.0 0.0 31114.0 0.0 35034.0 0.0 12111.0 0.0 24885.0 0.0 Compaction work is markedly reduced despite much better THP rates. In the vanilla kernel, reclaim seems to have been driven primarily by watermark boosting that happens as a result of fallbacks. With those all but eliminated, watermarks average lower and kswapd does less work. The uptick in direct reclaim is because THP requests have to fend for themselves more often - which is intended policy right now. Aggregate reclaim activity is lowered significantly, though. This patch (of 10): The idea behind the cache is to save get_pageblock_migratetype() lookups during bulk freeing. A microbenchmark suggests this isn't helping, though. The pcp migratetype can get stale, which means that bulk freeing has an extra branch to check if the pageblock was isolated while on the pcp. While the variance overlaps, the cache write and the branch seem to make this a net negative. The following test allocates and frees batches of 10,000 pages (~3x the pcp high marks to trigger flushing): Before: 8,668.48 msec task-clock # 99.735 CPUs utilized ( +- 2.90% ) 19 context-switches # 4.341 /sec ( +- 3.24% ) 0 cpu-migrations # 0.000 /sec 17,440 page-faults # 3.984 K/sec ( +- 2.90% ) 41,758,692,473 cycles # 9.541 GHz ( +- 2.90% ) 126,201,294,231 instructions # 5.98 insn per cycle ( +- 2.90% ) 25,348,098,335 branches # 5.791 G/sec ( +- 2.90% ) 33,436,921 branch-misses # 0.26% of all branches ( +- 2.90% ) 0.0869148 +- 0.0000302 seconds time elapsed ( +- 0.03% ) After: 8,444.81 msec task-clock # 99.726 CPUs utilized ( +- 2.90% ) 22 context-switches # 5.160 /sec ( +- 3.23% ) 0 cpu-migrations # 0.000 /sec 17,443 page-faults # 4.091 K/sec ( +- 2.90% ) 40,616,738,355 cycles # 9.527 GHz ( +- 2.90% ) 126,383,351,792 instructions # 6.16 insn per cycle ( +- 2.90% ) 25,224,985,153 branches # 5.917 G/sec ( +- 2.90% ) 32,236,793 branch-misses # 0.25% of all branches ( +- 2.90% ) 0.0846799 +- 0.0000412 seconds time elapsed ( +- 0.05% ) A side effect is that this also ensures that pages whose pageblock gets stolen while on the pcplist end up on the right freelist and we don't perform potentially type-incompatible buddy merges (or skip merges when we shouldn't), which is likely beneficial to long-term fragmentation management, although the effects would be harder to measure. Settle for simpler and faster code as justification here. Link: https://lkml.kernel.org/r/20240320180429.678181-1-hannes@cmpxchg.org Link: https://lkml.kernel.org/r/20240320180429.678181-2-hannes@cmpxchg.org Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Zi Yan <ziy@nvidia.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Mel Gorman <mgorman@techsingularity.net> Tested-by: "Huang, Ying" <ying.huang@intel.com> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: David Hildenbrand <david@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: mm/page_alloc.c [ Context conflicts with commit 62b208c4859c and ae577de78c12. ] Signed-off-by: Liu Shixin <liushixin2@huawei.com> Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- mm/page_alloc.c | 66 +++++++++++-------------------------------------- 1 file changed, 14 insertions(+), 52 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 776fabffb96e..6fced070bd35 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -207,24 +207,6 @@ EXPORT_SYMBOL(node_states); gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; -/* - * A cached value of the page's pageblock's migratetype, used when the page is - * put on a pcplist. Used to avoid the pageblock migratetype lookup when - * freeing from pcplists in most cases, at the cost of possibly becoming stale. - * Also the migratetype set in the page does not necessarily match the pcplist - * index, e.g. page might have MIGRATE_CMA set but be on a pcplist with any - * other index - this ensures that it will be put on the correct CMA freelist. - */ -static inline int get_pcppage_migratetype(struct page *page) -{ - return page->index; -} - -static inline void set_pcppage_migratetype(struct page *page, int migratetype) -{ - page->index = migratetype; -} - #ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE unsigned int pageblock_order __read_mostly; #endif @@ -1201,7 +1183,6 @@ static void free_pcppages_bulk(struct zone *zone, int count, { unsigned long flags; unsigned int order; - bool isolated_pageblocks; struct page *page; /* @@ -1214,7 +1195,6 @@ static void free_pcppages_bulk(struct zone *zone, int count, pindex = pindex - 1; spin_lock_irqsave(&zone->lock, flags); - isolated_pageblocks = has_isolate_pageblock(zone); while (count > 0) { struct list_head *list; @@ -1230,23 +1210,19 @@ static void free_pcppages_bulk(struct zone *zone, int count, order = pindex_to_order(pindex); nr_pages = 1 << order; do { + unsigned long pfn; int mt; page = list_last_entry(list, struct page, pcp_list); - mt = get_pcppage_migratetype(page); + pfn = page_to_pfn(page); + mt = get_pfnblock_migratetype(page, pfn); /* must delete to avoid corrupting pcp list */ list_del(&page->pcp_list); count -= nr_pages; pcp->count -= nr_pages; - /* MIGRATE_ISOLATE page should not go to pcplists */ - VM_BUG_ON_PAGE(is_migrate_isolate(mt), page); - /* Pageblock could have been isolated meanwhile */ - if (unlikely(isolated_pageblocks)) - mt = get_pageblock_migratetype(page); - - __free_one_page(page, page_to_pfn(page), zone, order, mt, FPI_NONE); + __free_one_page(page, pfn, zone, order, mt, FPI_NONE); trace_mm_page_pcpu_drain(page, order, mt); } while (count > 0 && !list_empty(list)); } @@ -1606,7 +1582,6 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order, continue; del_page_from_free_list(page, zone, current_order); expand(zone, page, order, current_order, migratetype); - set_pcppage_migratetype(page, migratetype); trace_mm_page_alloc_zone_locked(page, order, migratetype, pcp_allowed_order(order) && migratetype < MIGRATE_PCPTYPES); @@ -2177,7 +2152,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, * pages are ordered properly. */ list_add_tail(&page->pcp_list, list); - if (is_migrate_cma(get_pcppage_migratetype(page))) + if (is_migrate_cma(get_pageblock_migratetype(page))) __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, -(1 << order)); } @@ -2377,19 +2352,6 @@ void drain_all_pages(struct zone *zone) __drain_all_pages(zone, false); } -static bool free_unref_page_prepare(struct page *page, unsigned long pfn, - unsigned int order) -{ - int migratetype; - - if (!free_pages_prepare(page, order)) - return false; - - migratetype = get_pfnblock_migratetype(page, pfn); - set_pcppage_migratetype(page, migratetype); - return true; -} - static int nr_pcp_free(struct per_cpu_pages *pcp, int batch, int high, bool free_high) { int min_nr_free, max_nr_free; @@ -2532,7 +2494,7 @@ void free_unref_page(struct page *page, unsigned int order) return; } - if (!free_unref_page_prepare(page, pfn, order)) + if (!free_pages_prepare(page, order)) return; /* @@ -2542,7 +2504,7 @@ void free_unref_page(struct page *page, unsigned int order) * get those areas back if necessary. Otherwise, we may have to free * excessively into the page allocator */ - migratetype = pcpmigratetype = get_pcppage_migratetype(page); + migratetype = pcpmigratetype = get_pfnblock_migratetype(page, pfn); if (unlikely(migratetype >= MIGRATE_PCPTYPES)) { if (unlikely(is_migrate_isolate(migratetype))) { free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE); @@ -2584,14 +2546,14 @@ void free_unref_folios(struct folio_batch *folios) continue; } - if (!free_unref_page_prepare(&folio->page, pfn, order)) + if (!free_pages_prepare(&folio->page, order)) continue; /* * Free isolated folios and orders not handled on the PCP * directly to the allocator, see comment in free_unref_page. */ - migratetype = get_pcppage_migratetype(&folio->page); + migratetype = get_pfnblock_migratetype(&folio->page, pfn); if (!pcp_allowed_order(order) || is_migrate_isolate(migratetype)) { free_one_page(folio_zone(folio), &folio->page, pfn, @@ -2608,10 +2570,11 @@ void free_unref_folios(struct folio_batch *folios) for (i = 0; i < folios->nr; i++) { struct folio *folio = folios->folios[i]; struct zone *zone = folio_zone(folio); + unsigned long pfn = folio_pfn(folio); unsigned int order = (unsigned long)folio->private; folio->private = NULL; - migratetype = get_pcppage_migratetype(&folio->page); + migratetype = get_pfnblock_migratetype(&folio->page, pfn); /* Different zone requires a different pcp lock */ if (zone != locked_zone) { @@ -2628,9 +2591,8 @@ void free_unref_folios(struct folio_batch *folios) pcp = pcp_spin_trylock(zone->per_cpu_pageset); if (unlikely(!pcp)) { pcp_trylock_finish(UP_flags); - free_one_page(zone, &folio->page, - folio_pfn(folio), order, - migratetype, FPI_NONE); + free_one_page(zone, &folio->page, pfn, + order, migratetype, FPI_NONE); locked_zone = NULL; continue; } @@ -2799,7 +2761,7 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, } } __mod_zone_freepage_state(zone, -(1 << order), - get_pcppage_migratetype(page)); + get_pageblock_migratetype(page)); spin_unlock_irqrestore(&zone->lock, flags); } while (check_new_pages(page, order)); -- 2.43.0