| Message ID | 20220215145111.27082-5-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Follow-up on high-order PCP caching | expand |
On 2/15/22 15:51, Mel Gorman wrote: > free_pcppages_bulk() has taken two passes through the pcp lists since > commit 0a5f4e5b4562 ("mm/free_pcppages_bulk: do not hold lock when picking > pages to free") due to deferring the cost of selecting PCP lists until > the zone lock is held. Now that list selection is simplier, the main > cost during selection is bulkfree_pcp_prepare() which in the normal case > is a simple check and prefetching. As the list manipulations have cost > in itself, go back to freeing pages in a single pass. > > The series up to this point was evaulated using a trunc microbenchmark > that is truncating sparse files stored in page cache (mmtests config > config-io-trunc). Sparse files were used to limit filesystem interaction. > > The results versus a revert of storing high-order pages in the PCP lists is > > 1-socket Skylake > 5.17.0-rc3 5.17.0-rc3 5.17.0-rc3 > vanilla mm-reverthighpcp-v1r1 mm-highpcpopt-v1 > Min elapsed 540.00 ( 0.00%) 530.00 ( 1.85%) 530.00 ( 1.85%) > Amean elapsed 543.00 ( 0.00%) 530.00 * 2.39%* 530.00 * 2.39%* > Stddev elapsed 4.83 ( 0.00%) 0.00 ( 100.00%) 0.00 ( 100.00%) > CoeffVar elapsed 0.89 ( 0.00%) 0.00 ( 100.00%) 0.00 ( 100.00%) > Max elapsed 550.00 ( 0.00%) 530.00 ( 3.64%) 530.00 ( 3.64%) > BAmean-50 elapsed 540.00 ( 0.00%) 530.00 ( 1.85%) 530.00 ( 1.85%) > BAmean-95 elapsed 542.22 ( 0.00%) 530.00 ( 2.25%) 530.00 ( 2.25%) > BAmean-99 elapsed 542.22 ( 0.00%) 530.00 ( 2.25%) 530.00 ( 2.25%) > > 2-socket CascadeLake > 5.17.0-rc3 5.17.0-rc3 5.17.0-rc3 > vanilla mm-reverthighpcp-v1 mm-highpcpopt-v1 > Min elapsed 510.00 ( 0.00%) 500.00 ( 1.96%) 500.00 ( 1.96%) > Amean elapsed 529.00 ( 0.00%) 521.00 ( 1.51%) 516.00 * 2.46%* > Stddev elapsed 16.63 ( 0.00%) 12.87 ( 22.64%) 9.66 ( 41.92%) > CoeffVar elapsed 3.14 ( 0.00%) 2.47 ( 21.46%) 1.87 ( 40.45%) > Max elapsed 550.00 ( 0.00%) 540.00 ( 1.82%) 530.00 ( 3.64%) > BAmean-50 elapsed 516.00 ( 0.00%) 512.00 ( 0.78%) 510.00 ( 1.16%) > BAmean-95 elapsed 526.67 ( 0.00%) 518.89 ( 1.48%) 514.44 ( 2.32%) > BAmean-99 elapsed 526.67 ( 0.00%) 518.89 ( 1.48%) 514.44 ( 2.32%) > > The original motivation for multi-passes was will-it-scale page_fault1 > using $nr_cpu processes. > > 2-socket CascadeLake (40 cores, 80 CPUs HT enabled) > 5.17.0-rc3 5.17.0-rc3 > vanilla mm-highpcpopt-v1r4 > Hmean page_fault1-processes-2 2694662.26 ( 0.00%) 2696801.07 ( 0.08%) > Hmean page_fault1-processes-5 6425819.34 ( 0.00%) 6426573.21 ( 0.01%) > Hmean page_fault1-processes-8 9642169.10 ( 0.00%) 9647444.94 ( 0.05%) > Hmean page_fault1-processes-12 12167502.10 ( 0.00%) 12073323.10 * -0.77%* > Hmean page_fault1-processes-21 15636859.03 ( 0.00%) 15587449.50 * -0.32%* > Hmean page_fault1-processes-30 25157348.61 ( 0.00%) 25111707.15 * -0.18%* > Hmean page_fault1-processes-48 27694013.85 ( 0.00%) 27728568.63 ( 0.12%) > Hmean page_fault1-processes-79 25928742.64 ( 0.00%) 25920933.41 ( -0.03%) <--- > Hmean page_fault1-processes-110 25730869.75 ( 0.00%) 25695727.57 * -0.14%* > Hmean page_fault1-processes-141 25626992.42 ( 0.00%) 25675346.68 * 0.19%* > Hmean page_fault1-processes-172 25611651.35 ( 0.00%) 25650940.14 * 0.15%* > Hmean page_fault1-processes-203 25577298.75 ( 0.00%) 25584848.65 ( 0.03%) > Hmean page_fault1-processes-234 25580686.07 ( 0.00%) 25601794.52 * 0.08%* > Hmean page_fault1-processes-265 25570215.47 ( 0.00%) 25553191.25 ( -0.07%) > Hmean page_fault1-processes-296 25549488.62 ( 0.00%) 25530311.58 ( -0.08%) > Hmean page_fault1-processes-320 25555149.05 ( 0.00%) 25585059.83 ( 0.12%) > > The differences are mostly within the noise and the difference close to > $nr_cpus is negligible. > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5e8c7cbe7a41..6881175b27df 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1455,14 +1455,21 @@ static void free_pcppages_bulk(struct zone *zone, int count, unsigned int order; int prefetch_nr = READ_ONCE(pcp->batch); bool isolated_pageblocks; - struct page *page, *tmp; - LIST_HEAD(head); + struct page *page; /* * Ensure proper count is passed which otherwise would stuck in the * below while (list_empty(list)) loop. */ count = min(pcp->count, count); + + /* + * local_lock_irq held so equivalent to spin_lock_irqsave for + * both PREEMPT_RT and non-PREEMPT_RT configurations. + */ + spin_lock(&zone->lock); + isolated_pageblocks = has_isolate_pageblock(zone); + while (count > 0) { struct list_head *list; int nr_pages; @@ -1485,7 +1492,11 @@ static void free_pcppages_bulk(struct zone *zone, int count, nr_pages = 1 << order; BUILD_BUG_ON(MAX_ORDER >= (1<<NR_PCP_ORDER_WIDTH)); do { + int mt; + page = list_last_entry(list, struct page, lru); + mt = get_pcppage_migratetype(page); + /* must delete to avoid corrupting pcp list */ list_del(&page->lru); count -= nr_pages; @@ -1494,12 +1505,6 @@ static void free_pcppages_bulk(struct zone *zone, int count, if (bulkfree_pcp_prepare(page)) continue; - /* Encode order with the migratetype */ - page->index <<= NR_PCP_ORDER_WIDTH; - page->index |= order; - - list_add_tail(&page->lru, &head); - /* * We are going to put the page back to the global * pool, prefetch its buddy to speed up later access @@ -1513,36 +1518,18 @@ static void free_pcppages_bulk(struct zone *zone, int count, prefetch_buddy(page, order); prefetch_nr--; } - } while (count > 0 && !list_empty(list)); - } - - /* - * local_lock_irq held so equivalent to spin_lock_irqsave for - * both PREEMPT_RT and non-PREEMPT_RT configurations. - */ - spin_lock(&zone->lock); - isolated_pageblocks = has_isolate_pageblock(zone); - - /* - * Use safe version since after __free_one_page(), - * page->lru.next will not point to original list. - */ - list_for_each_entry_safe(page, tmp, &head, lru) { - int mt = get_pcppage_migratetype(page); - /* mt has been encoded with the order (see above) */ - order = mt & NR_PCP_ORDER_MASK; - mt >>= NR_PCP_ORDER_WIDTH; + /* 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); - /* 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); - trace_mm_page_pcpu_drain(page, order, mt); + __free_one_page(page, page_to_pfn(page), zone, order, mt, FPI_NONE); + trace_mm_page_pcpu_drain(page, order, mt); + } while (count > 0 && !list_empty(list)); } + spin_unlock(&zone->lock); }
free_pcppages_bulk() has taken two passes through the pcp lists since commit 0a5f4e5b4562 ("mm/free_pcppages_bulk: do not hold lock when picking pages to free") due to deferring the cost of selecting PCP lists until the zone lock is held. Now that list selection is simplier, the main cost during selection is bulkfree_pcp_prepare() which in the normal case is a simple check and prefetching. As the list manipulations have cost in itself, go back to freeing pages in a single pass. The series up to this point was evaulated using a trunc microbenchmark that is truncating sparse files stored in page cache (mmtests config config-io-trunc). Sparse files were used to limit filesystem interaction. The results versus a revert of storing high-order pages in the PCP lists is 1-socket Skylake 5.17.0-rc3 5.17.0-rc3 5.17.0-rc3 vanilla mm-reverthighpcp-v1r1 mm-highpcpopt-v1 Min elapsed 540.00 ( 0.00%) 530.00 ( 1.85%) 530.00 ( 1.85%) Amean elapsed 543.00 ( 0.00%) 530.00 * 2.39%* 530.00 * 2.39%* Stddev elapsed 4.83 ( 0.00%) 0.00 ( 100.00%) 0.00 ( 100.00%) CoeffVar elapsed 0.89 ( 0.00%) 0.00 ( 100.00%) 0.00 ( 100.00%) Max elapsed 550.00 ( 0.00%) 530.00 ( 3.64%) 530.00 ( 3.64%) BAmean-50 elapsed 540.00 ( 0.00%) 530.00 ( 1.85%) 530.00 ( 1.85%) BAmean-95 elapsed 542.22 ( 0.00%) 530.00 ( 2.25%) 530.00 ( 2.25%) BAmean-99 elapsed 542.22 ( 0.00%) 530.00 ( 2.25%) 530.00 ( 2.25%) 2-socket CascadeLake 5.17.0-rc3 5.17.0-rc3 5.17.0-rc3 vanilla mm-reverthighpcp-v1 mm-highpcpopt-v1 Min elapsed 510.00 ( 0.00%) 500.00 ( 1.96%) 500.00 ( 1.96%) Amean elapsed 529.00 ( 0.00%) 521.00 ( 1.51%) 516.00 * 2.46%* Stddev elapsed 16.63 ( 0.00%) 12.87 ( 22.64%) 9.66 ( 41.92%) CoeffVar elapsed 3.14 ( 0.00%) 2.47 ( 21.46%) 1.87 ( 40.45%) Max elapsed 550.00 ( 0.00%) 540.00 ( 1.82%) 530.00 ( 3.64%) BAmean-50 elapsed 516.00 ( 0.00%) 512.00 ( 0.78%) 510.00 ( 1.16%) BAmean-95 elapsed 526.67 ( 0.00%) 518.89 ( 1.48%) 514.44 ( 2.32%) BAmean-99 elapsed 526.67 ( 0.00%) 518.89 ( 1.48%) 514.44 ( 2.32%) The original motivation for multi-passes was will-it-scale page_fault1 using $nr_cpu processes. 2-socket CascadeLake (40 cores, 80 CPUs HT enabled) 5.17.0-rc3 5.17.0-rc3 vanilla mm-highpcpopt-v1r4 Hmean page_fault1-processes-2 2694662.26 ( 0.00%) 2696801.07 ( 0.08%) Hmean page_fault1-processes-5 6425819.34 ( 0.00%) 6426573.21 ( 0.01%) Hmean page_fault1-processes-8 9642169.10 ( 0.00%) 9647444.94 ( 0.05%) Hmean page_fault1-processes-12 12167502.10 ( 0.00%) 12073323.10 * -0.77%* Hmean page_fault1-processes-21 15636859.03 ( 0.00%) 15587449.50 * -0.32%* Hmean page_fault1-processes-30 25157348.61 ( 0.00%) 25111707.15 * -0.18%* Hmean page_fault1-processes-48 27694013.85 ( 0.00%) 27728568.63 ( 0.12%) Hmean page_fault1-processes-79 25928742.64 ( 0.00%) 25920933.41 ( -0.03%) <--- Hmean page_fault1-processes-110 25730869.75 ( 0.00%) 25695727.57 * -0.14%* Hmean page_fault1-processes-141 25626992.42 ( 0.00%) 25675346.68 * 0.19%* Hmean page_fault1-processes-172 25611651.35 ( 0.00%) 25650940.14 * 0.15%* Hmean page_fault1-processes-203 25577298.75 ( 0.00%) 25584848.65 ( 0.03%) Hmean page_fault1-processes-234 25580686.07 ( 0.00%) 25601794.52 * 0.08%* Hmean page_fault1-processes-265 25570215.47 ( 0.00%) 25553191.25 ( -0.07%) Hmean page_fault1-processes-296 25549488.62 ( 0.00%) 25530311.58 ( -0.08%) Hmean page_fault1-processes-320 25555149.05 ( 0.00%) 25585059.83 ( 0.12%) The differences are mostly within the noise and the difference close to $nr_cpus is negligible. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> --- mm/page_alloc.c | 57 +++++++++++++++++++------------------------------ 1 file changed, 22 insertions(+), 35 deletions(-)