On Sat, 13 Jun 2020 01:05:52 +0200 Pavel Machek wrote: > > > +CC linux-mm > > > > > > On 5/31/20 12:34 PM, Pavel Machek wrote: > > > > Hi! > > > > > > > > This is simple cat /dev/sda > /dev/zero... on thinkpad x60 (x86-32), > > > > with spinning rust. > > > > > > > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > > > > 1000 root 20 0 0 0 0 R 53.3 0.0 57:34.93 kswapd0 > > > > 27897 root 20 0 6976 580 536 R 44.5 0.0 1:44.53 cat > > > > > > > > It keeps both CPUs busy... and I don't think that's right. > > > > > > Does an older kernel behave differently here? > > > > Let me try on x220 (x86-64, first): > > > > 737 root 20 0 5404 744 680 R 31.2 0.0 0:09.98 cat > > 1024 root 20 0 0 0 0 S 21.4 0.0 165:22.68 kswapd0 > > > > That was with ssd, result with spinning rust is similar: > > > > 859 root 20 0 5404 740 672 D 21.1 0.0 0:03.33 cat > > 1024 root 20 0 0 0 0 R 11.8 0.0 165:33.07 kswapd0 > > > > 5.7-rc1+ kernel. > > > > Performance of spinning rust is down, too, on x60: > > > > pavel@amd:~/misc/hw/hdd1t$ sudo ddrescue --force /dev/sda1 /dev/null > > GNU ddrescue 1.19 > > Press Ctrl-C to interrupt > > rescued: 2147 MB, errsize: 0 B, current rate: 3080 kB/s > > ipos: 2147 MB, errors: 0, average rate: 5382 kB/s > > opos: 2147 MB, run time: 6.65 m, successful read: > > 0 s ago > > Finished > > pavel@amd:~/misc/hw/hdd1t$ uname -a > > Linux amd 5.7.0-next-20200611+ #123 SMP PREEMPT Thu Jun 11 > > 15:41:22 CEST 2020 i686 GNU/Linux > > > > And there's something clearly wrong here: > > > > 966 root 20 0 0 0 0 R 94.4 0.0 8:18.82 kswapd0 > > 23933 root 20 0 4612 1112 1028 D 80.6 0.0 0:26.40 ddrescue > > > > Same x60 under older kernel: > > pavel@amd:/data/fast/pavel$ sudo ddrescue --force /dev/sda4 /dev/null > GNU ddrescue 1.19 > Press Ctrl-C to interrupt > rescued: 6593 MB, errsize: 0 B, current rate: 60424 kB/s > ipos: 6593 MB, errors: 0, average rate: 95563 kB/s > > 3539 root 20 0 4616 1136 1048 D 21.4 0.0 0:15.63 ddrescue > 865 root 20 0 0 0 0 S 6.9 0.0 0:04.91 kswapd0 > > Linux amd 4.6.0+ #172 SMP Sun Aug 14 11:25:34 CEST 2016 i686 GNU/Linux > > These are more reasonable numbers. Treat referenced & active pages as reclaim cost. --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2020,6 +2020,7 @@ static void shrink_active_list(unsigned struct page *page; unsigned nr_deactivate, nr_activate; unsigned nr_rotated = 0; + unsigned nr_refered = 0; int file = is_file_lru(lru); struct pglist_data *pgdat = lruvec_pgdat(lruvec); @@ -2070,7 +2071,8 @@ static void shrink_active_list(unsigned nr_rotated += hpage_nr_pages(page); list_add(&page->lru, &l_active); continue; - } + } else if (!file) + nr_refered++; } ClearPageActive(page); /* we are de-activating */ @@ -2098,6 +2100,14 @@ static void shrink_active_list(unsigned free_unref_page_list(&l_active); trace_mm_vmscan_lru_shrink_active(pgdat->node_id, nr_taken, nr_activate, nr_deactivate, nr_rotated, sc->priority, file); + if (file) + sc->file_cost += nr_rotated; + else + /* + * add cost to avoid swapin in the near future which incurs IO + * on top of reclaim + */ + sc->anon_cost += nr_refered; } unsigned long reclaim_pages(struct list_head *page_list) @@ -2311,11 +2321,13 @@ static void get_scan_count(struct lruvec file_cost = total_cost + sc->file_cost; total_cost = anon_cost + file_cost; - ap = swappiness * (total_cost + 1); - ap /= anon_cost + 1; - - fp = (200 - swappiness) * (total_cost + 1); - fp /= file_cost + 1; + ap = swappiness * total_cost; + if (anon_cost) + ap /= anon_cost; + + fp = (200 - swappiness) * total_cost; + if (file_cost) + fp /= file_cost; fraction[0] = ap; fraction[1] = fp;
