* 5.7-rc0: kswapd eats cpu during a disk test?! @ 2020-05-31 10:34 Pavel Machek 2020-06-01 8:55 ` Vlastimil Babka 0 siblings, 1 reply; 5+ messages in thread From: Pavel Machek @ 2020-05-31 10:34 UTC (permalink / raw) To: kernel list, Andrew Morton; +Cc: mhocko, vbabka [-- Attachment #1: Type: text/plain, Size: 537 bytes --] 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. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 181 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: 5.7-rc0: kswapd eats cpu during a disk test?! 2020-05-31 10:34 5.7-rc0: kswapd eats cpu during a disk test?! Pavel Machek @ 2020-06-01 8:55 ` Vlastimil Babka 2020-06-12 22:45 ` Pavel Machek 0 siblings, 1 reply; 5+ messages in thread From: Vlastimil Babka @ 2020-06-01 8:55 UTC (permalink / raw) To: Pavel Machek, kernel list, Andrew Morton; +Cc: mhocko, linux-mm +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? ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: 5.7-rc0: kswapd eats cpu during a disk test?! 2020-06-01 8:55 ` Vlastimil Babka @ 2020-06-12 22:45 ` Pavel Machek 2020-06-12 23:05 ` Pavel Machek [not found] ` <20200613044738.11764-1-hdanton@sina.com> 0 siblings, 2 replies; 5+ messages in thread From: Pavel Machek @ 2020-06-12 22:45 UTC (permalink / raw) To: Vlastimil Babka; +Cc: kernel list, Andrew Morton, mhocko, linux-mm [-- Attachment #1: Type: text/plain, Size: 1909 bytes --] Hi! > +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 -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 181 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: 5.7-rc0: kswapd eats cpu during a disk test?! 2020-06-12 22:45 ` Pavel Machek @ 2020-06-12 23:05 ` Pavel Machek [not found] ` <20200613044738.11764-1-hdanton@sina.com> 1 sibling, 0 replies; 5+ messages in thread From: Pavel Machek @ 2020-06-12 23:05 UTC (permalink / raw) To: Vlastimil Babka; +Cc: kernel list, Andrew Morton, mhocko, linux-mm [-- Attachment #1: Type: text/plain, Size: 2585 bytes --] Hi! > > +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. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 181 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
[parent not found: <20200613044738.11764-1-hdanton@sina.com>]
* Re: 5.7-rc0: kswapd eats cpu during a disk test?! [not found] ` <20200613044738.11764-1-hdanton@sina.com> @ 2020-06-13 6:48 ` Pavel Machek 0 siblings, 0 replies; 5+ messages in thread From: Pavel Machek @ 2020-06-13 6:48 UTC (permalink / raw) To: Hillf Danton Cc: Vlastimil Babka, kernel list, Andrew Morton, mhocko, linux mm [-- Attachment #1: Type: text/plain, Size: 4006 bytes --] Hi! > > > 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. That helps a bit, but we are still nowehere near v4.6 performance: pavel@amd:/data/fast/pavel$ sudo ddrescue --force /dev/sda2 /dev/null GNU ddrescue 1.19 Press Ctrl-C to interrupt rescued: 8559 MB, errsize: 0 B, current rate: 53084 kB/s ipos: 8559 MB, errors: 0, average rate: 71327 kB/s 3933 root 20 0 4612 1216 1128 R 68.6 0.0 0:12.14 ddrescue 967 root 20 0 0 0 0 R 64.4 0.0 1:18.67 kswapd0 (I applied the patch on 5.7.0-next-20200611+). Do we know which original change is causing this? Any other ideas? Thanks, Pavel > --- 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; -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html [-- Attachment #2: Digital signature --] [-- Type: application/pgp-signature, Size: 181 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-05-31 10:34 5.7-rc0: kswapd eats cpu during a disk test?! Pavel Machek
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2020-06-12 23:05 ` Pavel Machek
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