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Message-ID: <CAGWkznEqhHcAb0ZnO9-ssk1qQHYFKx4ML0vd4Knj_f2n_PpR0g@mail.gmail.com> Date: Tue, 23 Apr 2019 19:43:18 +0800 From: Zhaoyang Huang <huangzhaoyang@...il.com> To: Matthew Wilcox <willy@...radead.org> Cc: Michal Hocko <mhocko@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, Joonsoo Kim <iamjoonsoo.kim@....com>, David Rientjes <rientjes@...gle.com>, Zhaoyang Huang <zhaoyang.huang@...soc.com>, Roman Gushchin <guro@...com>, Jeff Layton <jlayton@...hat.com>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Pavel Tatashin <pasha.tatashin@...een.com>, Johannes Weiner <hannes@...xchg.org> Subject: Re: [RFC PATCH] mm/workingset : judge file page activity via timestamp rebase the commit to latest mainline and update the code. @Matthew, with regarding to your comment, I would like to say the algorithm doesn't change at all. I do NOT judge the page's activity via an absolute time value, but still the refault distance. What I want to fix is the scenario which drop lots of file pages on this lru that leading to a big refault_distance(inactive_age) and inactivate the page. I haven't found regression of the commit yet. Could you please suggest me more test cases? Thank you! diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index fba7741..ca4ced6 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -242,6 +242,7 @@ struct lruvec { atomic_long_t inactive_age; /* Refaults at the time of last reclaim cycle */ unsigned long refaults; + atomic_long_t refaults_ratio; #ifdef CONFIG_MEMCG struct pglist_data *pgdat; #endif diff --git a/mm/workingset.c b/mm/workingset.c index 0bedf67..95683c1 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -171,6 +171,15 @@ 1 + NODES_SHIFT + MEM_CGROUP_ID_SHIFT) #define EVICTION_MASK (~0UL >> EVICTION_SHIFT) +#ifdef CONFIG_64BIT +#define EVICTION_SECS_POS_SHIFT 19 +#define EVICTION_SECS_SHRINK_SHIFT 4 +#define EVICTION_SECS_POS_MASK ((1UL << EVICTION_SECS_POS_SHIFT) - 1) +#else +#define EVICTION_SECS_POS_SHIFT 0 +#define EVICTION_SECS_SHRINK_SHIFT 0 +#define NO_SECS_IN_WORKINGSET +#endif /* * Eviction timestamps need to be able to cover the full range of * actionable refaults. However, bits are tight in the xarray @@ -180,12 +189,48 @@ * evictions into coarser buckets by shaving off lower timestamp bits. */ static unsigned int bucket_order __read_mostly; - +#ifdef NO_SECS_IN_WORKINGSET +static void pack_secs(unsigned long *peviction) { } +static unsigned int unpack_secs(unsigned long entry) {return 0; } +#else +static void pack_secs(unsigned long *peviction) +{ + unsigned int secs; + unsigned long eviction; + int order; + int secs_shrink_size; + struct timespec64 ts; + + ktime_get_boottime_ts64(&ts); + secs = (unsigned int)ts.tv_sec ? (unsigned int)ts.tv_sec : 1; + order = get_count_order(secs); + secs_shrink_size = (order <= EVICTION_SECS_POS_SHIFT) + ? 0 : (order - EVICTION_SECS_POS_SHIFT); + + eviction = *peviction; + eviction = (eviction << EVICTION_SECS_POS_SHIFT) + | ((secs >> secs_shrink_size) & EVICTION_SECS_POS_MASK); + eviction = (eviction << EVICTION_SECS_SHRINK_SHIFT) | (secs_shrink_size & 0xf); + *peviction = eviction; +} +static unsigned int unpack_secs(unsigned long entry) +{ + unsigned int secs; + int secs_shrink_size; + + secs_shrink_size = entry & ((1 << EVICTION_SECS_SHRINK_SHIFT) - 1); + entry >>= EVICTION_SECS_SHRINK_SHIFT; + secs = entry & EVICTION_SECS_POS_MASK; + secs = secs << secs_shrink_size; + return secs; +} +#endif static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction, bool workingset) { eviction >>= bucket_order; eviction &= EVICTION_MASK; + pack_secs(&eviction); eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid; eviction = (eviction << NODES_SHIFT) | pgdat->node_id; eviction = (eviction << 1) | workingset; @@ -194,11 +239,12 @@ static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction, } static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, - unsigned long *evictionp, bool *workingsetp) + unsigned long *evictionp, bool *workingsetp, unsigned int *prev_secs) { unsigned long entry = xa_to_value(shadow); int memcgid, nid; bool workingset; + unsigned int secs; workingset = entry & 1; entry >>= 1; @@ -206,11 +252,14 @@ static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, entry >>= NODES_SHIFT; memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1); entry >>= MEM_CGROUP_ID_SHIFT; + secs = unpack_secs(entry); + entry >>= (EVICTION_SECS_POS_SHIFT + EVICTION_SECS_SHRINK_SHIFT); *memcgidp = memcgid; *pgdat = NODE_DATA(nid); *evictionp = entry << bucket_order; *workingsetp = workingset; + *prev_secs = secs; } /** @@ -257,8 +306,22 @@ void workingset_refault(struct page *page, void *shadow) unsigned long refault; bool workingset; int memcgid; +#ifndef NO_SECS_IN_WORKINGSET + unsigned long avg_refault_time; + unsigned long refaults_ratio; + unsigned long refault_time; + int tradition; + unsigned int prev_secs; + unsigned int secs; +#endif + struct timespec64 ts; + /* + convert jiffies to second + */ + ktime_get_boottime_ts64(&ts); + secs = (unsigned int)ts.tv_sec ? (unsigned int)ts.tv_sec : 1; - unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset); + unpack_shadow(shadow, &memcgid, &pgdat, &eviction, &workingset, &prev_secs); rcu_read_lock(); /* @@ -303,23 +366,58 @@ void workingset_refault(struct page *page, void *shadow) refault_distance = (refault - eviction) & EVICTION_MASK; inc_lruvec_state(lruvec, WORKINGSET_REFAULT); - +#ifndef NO_SECS_IN_WORKINGSET + refaults_ratio = (atomic_long_read(&lruvec->inactive_age) + 1) / secs; + atomic_long_set(&lruvec->refaults_ratio, refaults_ratio); + refault_time = secs - prev_secs; + avg_refault_time = active_file / refaults_ratio; + tradition = !!(refault_distance < active_file); /* - * Compare the distance to the existing workingset size. We - * don't act on pages that couldn't stay resident even if all - * the memory was available to the page cache. + * What we are trying to solve here is + * 1. extremely fast refault as refault_time == 0. + * 2. quick file drop scenario, which has a big refault_distance but + * small refault_time comparing with the past refault ratio, which + * will be deemed as inactive in previous implementation. */ - if (refault_distance > active_file) + if (refault_time && (((refault_time < avg_refault_time) + && (avg_refault_time < 2 * refault_time)) + || (refault_time >= avg_refault_time))) { + trace_printk("WKST_INACT[%d]:rft_dis %ld, act %ld\ + rft_ratio %ld rft_time %ld avg_rft_time %ld\ + refault %ld eviction %ld secs %d pre_secs %d page %p\n", + tradition, refault_distance, active_file, + refaults_ratio, refault_time, avg_refault_time, + refault, eviction, secs, prev_secs, page); goto out; + } + else { +#else + if (refault_distance < active_file) { +#endif - SetPageActive(page); - atomic_long_inc(&lruvec->inactive_age); - inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE); + /* + * Compare the distance to the existing workingset size. We + * don't act on pages that couldn't stay resident even if all + * the memory was available to the page cache. + */ - /* Page was active prior to eviction */ - if (workingset) { - SetPageWorkingset(page); - inc_lruvec_state(lruvec, WORKINGSET_RESTORE); + SetPageActive(page); + atomic_long_inc(&lruvec->inactive_age); + inc_lruvec_state(lruvec, WORKINGSET_ACTIVATE); + + /* Page was active prior to eviction */ + if (workingset) { + SetPageWorkingset(page); + inc_lruvec_state(lruvec, WORKINGSET_RESTORE); + } +#ifndef NO_SECS_IN_WORKINGSET + trace_printk("WKST_ACT[%d]:rft_dis %ld, act %ld\ + rft_ratio %ld rft_time %ld avg_rft_time %ld\ + refault %ld eviction %ld secs %d pre_secs %d page %p\n", + tradition, refault_distance, active_file, + refaults_ratio, refault_time, avg_refault_time, + refault, eviction, secs, prev_secs, page); +#endif } out: rcu_read_unlock(); @@ -539,7 +637,9 @@ static int __init workingset_init(void) unsigned int max_order; int ret; - BUILD_BUG_ON(BITS_PER_LONG < EVICTION_SHIFT); + BUILD_BUG_ON(BITS_PER_LONG < (EVICTION_SHIFT + + EVICTION_SECS_POS_SHIFT + + EVICTION_SECS_SHRINK_SHIFT)); /* * Calculate the eviction bucket size to cover the longest * actionable refault distance, which is currently half of @@ -547,7 +647,9 @@ static int __init workingset_init(void) * some more pages at runtime, so keep working with up to * double the initial memory by using totalram_pages as-is. */ - timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT; + timestamp_bits = BITS_PER_LONG - EVICTION_SHIFT + - EVICTION_SECS_POS_SHIFT - EVICTION_SECS_SHRINK_SHIFT; + max_order = fls_long(totalram_pages() - 1); if (max_order > timestamp_bits) bucket_order = max_order - timestamp_bits; On Wed, Apr 17, 2019 at 9:37 PM Matthew Wilcox <willy@...radead.org> wrote: > > On Wed, Apr 17, 2019 at 08:26:22PM +0800, Zhaoyang Huang wrote: > [quoting Johannes here] > > As Matthew says, you are fairly randomly making refault activations > > more aggressive (especially with that timestamp unpacking bug), and > > while that expectedly boosts workload transition / startup, it comes > > at the cost of disrupting stable states because you can flood a very > > active in-ram workingset with completely cold cache pages simply > > because they refault uniformly wrt each other. > > [HZY]: I analysis the log got from trace_printk, what we activate have > > proven record of long refault distance but very short refault time. > > You haven't addressed my point, which is that you were only testing > workloads for which your changed algorithm would improve the results. > What you haven't done is shown how other workloads would be negatively > affected. > > Once you do that, we can make a decision about whether to improve your > workload by X% and penalise that other workload by Y%.
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