Searched hist:52262 (Results 1 - 9 of 9) sorted by relevance
/linux-master/sound/synth/emux/ | ||
H A D | Makefile | diff 52262b4a Thu May 28 23:58:11 MDT 2015 Takashi Iwai <tiwai@suse.de> ALSA: emux: Fix/cleanup old ifdef CONFIG_PROC_FS Build emux_proc.o and drop the unneeded ifdefs. Replace the left CONFIG_PROC with the new CONFIG_SND_PROC_FS. Along with this, fix the build of emux_oss.o in Makefile, too. Signed-off-by: Takashi Iwai <tiwai@suse.de> |
H A D | emux_voice.h | diff 52262b4a Thu May 28 23:58:11 MDT 2015 Takashi Iwai <tiwai@suse.de> ALSA: emux: Fix/cleanup old ifdef CONFIG_PROC_FS Build emux_proc.o and drop the unneeded ifdefs. Replace the left CONFIG_PROC with the new CONFIG_SND_PROC_FS. Along with this, fix the build of emux_oss.o in Makefile, too. Signed-off-by: Takashi Iwai <tiwai@suse.de> |
H A D | emux_proc.c | diff 52262b4a Thu May 28 23:58:11 MDT 2015 Takashi Iwai <tiwai@suse.de> ALSA: emux: Fix/cleanup old ifdef CONFIG_PROC_FS Build emux_proc.o and drop the unneeded ifdefs. Replace the left CONFIG_PROC with the new CONFIG_SND_PROC_FS. Along with this, fix the build of emux_oss.o in Makefile, too. Signed-off-by: Takashi Iwai <tiwai@suse.de> |
H A D | emux.c | diff 52262b4a Thu May 28 23:58:11 MDT 2015 Takashi Iwai <tiwai@suse.de> ALSA: emux: Fix/cleanup old ifdef CONFIG_PROC_FS Build emux_proc.o and drop the unneeded ifdefs. Replace the left CONFIG_PROC with the new CONFIG_SND_PROC_FS. Along with this, fix the build of emux_oss.o in Makefile, too. Signed-off-by: Takashi Iwai <tiwai@suse.de> |
/linux-master/include/sound/ | ||
H A D | emux_synth.h | diff 52262b4a Thu May 28 23:58:11 MDT 2015 Takashi Iwai <tiwai@suse.de> ALSA: emux: Fix/cleanup old ifdef CONFIG_PROC_FS Build emux_proc.o and drop the unneeded ifdefs. Replace the left CONFIG_PROC with the new CONFIG_SND_PROC_FS. Along with this, fix the build of emux_oss.o in Makefile, too. Signed-off-by: Takashi Iwai <tiwai@suse.de> |
/linux-master/fs/btrfs/ | ||
H A D | relocation.c | diff 50e31ef4 Tue Dec 29 06:29:34 MST 2020 Qu Wenruo <wqu@suse.com> btrfs: reloc: fix wrong file extent type check to avoid false ENOENT [BUG] There are several bug reports about recent kernel unable to relocate certain data block groups. Sometimes the error just goes away, but there is one reporter who can reproduce it reliably. The dmesg would look like: [438.260483] BTRFS info (device dm-10): balance: start -dvrange=34625344765952..34625344765953 [438.269018] BTRFS info (device dm-10): relocating block group 34625344765952 flags data|raid1 [450.439609] BTRFS info (device dm-10): found 167 extents, stage: move data extents [463.501781] BTRFS info (device dm-10): balance: ended with status: -2 [CAUSE] The ENOENT error is returned from the following call chain: add_data_references() |- delete_v1_space_cache(); |- if (!found) return -ENOENT; The variable @found is set to true if we find a data extent whose disk bytenr matches parameter @data_bytes. With extra debugging, the offending tree block looks like this: leaf bytenr = 42676709441536, data_bytenr = 34626327621632 ctime 1567904822.739884119 (2019-09-08 03:07:02) mtime 0.0 (1970-01-01 01:00:00) otime 0.0 (1970-01-01 01:00:00) item 27 key (51933 EXTENT_DATA 0) itemoff 9854 itemsize 53 generation 1517381 type 2 (prealloc) prealloc data disk byte 34626327621632 nr 262144 <<< prealloc data offset 0 nr 262144 item 28 key (52262 ROOT_ITEM 0) itemoff 9415 itemsize 439 generation 2618893 root_dirid 256 bytenr 42677048360960 level 3 refs 1 lastsnap 2618893 byte_limit 0 bytes_used 5557338112 flags 0x0(none) uuid d0d4361f-d231-6d40-8901-fe506e4b2b53 Although item 27 has disk bytenr 34626327621632, which matches the data_bytenr, its type is prealloc, not reg. This makes the existing code skip that item, and return ENOENT. [FIX] The code is modified in commit 19b546d7a1b2 ("btrfs: relocation: Use btrfs_find_all_leafs to locate data extent parent tree leaves"), before that commit, we use something like "if (type == BTRFS_FILE_EXTENT_INLINE) continue;" But in that offending commit, we use (type == BTRFS_FILE_EXTENT_REG), ignoring BTRFS_FILE_EXTENT_PREALLOC. Fix it by also checking BTRFS_FILE_EXTENT_PREALLOC. Reported-by: Stéphane Lesimple <stephane_btrfs2@lesimple.fr> Link: https://lore.kernel.org/linux-btrfs/505cabfa88575ed6dbe7cb922d8914fb@lesimple.fr Fixes: 19b546d7a1b2 ("btrfs: relocation: Use btrfs_find_all_leafs to locate data extent parent tree leaves") CC: stable@vger.kernel.org # 5.6+ Tested-By: Stéphane Lesimple <stephane_btrfs2@lesimple.fr> Reviewed-by: Su Yue <l@damenly.su> Signed-off-by: Qu Wenruo <wqu@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
/linux-master/kernel/sched/ | ||
H A D | sched.h | diff 52262ee5 Tue Jan 28 08:40:06 MST 2020 Mel Gorman <mgorman@techsingularity.net> sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression The following XFS commit: 8ab39f11d974 ("xfs: prevent CIL push holdoff in log recovery") changed the logic from using bound workqueues to using unbound workqueues. Functionally this makes sense but it was observed at the time that the dbench performance dropped quite a lot and CPU migrations were increased. The current pattern of the task migration is straight-forward. With XFS, an IO issuer delegates work to xlog_cil_push_work ()on an unbound kworker. This runs on a nearby CPU and on completion, dbench wakes up on its old CPU as it is still idle and no migration occurs. dbench then queues the real IO on the blk_mq_requeue_work() work item which runs on a bound kworker which is forced to run on the same CPU as dbench. When IO completes, the bound kworker wakes dbench but as the kworker is a bound but, real task, the CPU is not considered idle and dbench gets migrated by select_idle_sibling() to a new CPU. dbench may ping-pong between two CPUs for a while but ultimately it starts a round-robin of all CPUs sharing the same LLC. High-frequency migration on each IO completion has poor performance overall. It has negative implications both in commication costs and power management. mpstat confirmed that at low thread counts that all CPUs sharing an LLC has low level of activity. Note that even if the CIL patch was reverted, there still would be migrations but the impact is less noticeable. It turns out that individually the scheduler, XFS, blk-mq and workqueues all made sensible decisions but in combination, the overall effect was sub-optimal. This patch special cases the IO issue/completion pattern and allows a bound kworker waker and a task wakee to stack on the same CPU if there is a strong chance they are directly related. The expectation is that the kworker is likely going back to sleep shortly. This is not guaranteed as the IO could be queued asynchronously but there is a very strong relationship between the task and kworker in this case that would justify stacking on the same CPU instead of migrating. There should be few concerns about kworker starvation given that the special casing is only when the kworker is the waker. DBench on XFS MMTests config: io-dbench4-async modified to run on a fresh XFS filesystem UMA machine with 8 cores sharing LLC 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack Amean 1 22.63 ( 0.00%) 20.54 * 9.23%* Amean 2 25.56 ( 0.00%) 23.40 * 8.44%* Amean 4 28.63 ( 0.00%) 27.85 * 2.70%* Amean 8 37.66 ( 0.00%) 37.68 ( -0.05%) Amean 64 469.47 ( 0.00%) 468.26 ( 0.26%) Stddev 1 1.00 ( 0.00%) 0.72 ( 28.12%) Stddev 2 1.62 ( 0.00%) 1.97 ( -21.54%) Stddev 4 2.53 ( 0.00%) 3.58 ( -41.19%) Stddev 8 5.30 ( 0.00%) 5.20 ( 1.92%) Stddev 64 86.36 ( 0.00%) 94.53 ( -9.46%) NUMA machine, 48 CPUs total, 24 CPUs share cache 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Amean 1 58.69 ( 0.00%) 30.21 * 48.53%* Amean 2 60.90 ( 0.00%) 35.29 * 42.05%* Amean 4 66.77 ( 0.00%) 46.55 * 30.28%* Amean 8 81.41 ( 0.00%) 68.46 * 15.91%* Amean 16 113.29 ( 0.00%) 107.79 * 4.85%* Amean 32 199.10 ( 0.00%) 198.22 * 0.44%* Amean 64 478.99 ( 0.00%) 477.06 * 0.40%* Amean 128 1345.26 ( 0.00%) 1372.64 * -2.04%* Stddev 1 2.64 ( 0.00%) 4.17 ( -58.08%) Stddev 2 4.35 ( 0.00%) 5.38 ( -23.73%) Stddev 4 6.77 ( 0.00%) 6.56 ( 3.00%) Stddev 8 11.61 ( 0.00%) 10.91 ( 6.04%) Stddev 16 18.63 ( 0.00%) 19.19 ( -3.01%) Stddev 32 38.71 ( 0.00%) 38.30 ( 1.06%) Stddev 64 100.28 ( 0.00%) 91.24 ( 9.02%) Stddev 128 186.87 ( 0.00%) 160.34 ( 14.20%) Dbench has been modified to report the time to complete a single "load file". This is a more meaningful metric for dbench that a throughput metric as the benchmark makes many different system calls that are not throughput-related Patch shows a 9.23% and 48.53% reduction in the time to process a load file with the difference partially explained by the number of CPUs sharing a LLC. In a separate run, task migrations were almost eliminated by the patch for low client counts. In case people have issue with the metric used for the benchmark, this is a comparison of the throughputs as reported by dbench on the NUMA machine. dbench4 Throughput (misleading but traditional) 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Hmean 1 321.41 ( 0.00%) 617.82 * 92.22%* Hmean 2 622.87 ( 0.00%) 1066.80 * 71.27%* Hmean 4 1134.56 ( 0.00%) 1623.74 * 43.12%* Hmean 8 1869.96 ( 0.00%) 2212.67 * 18.33%* Hmean 16 2673.11 ( 0.00%) 2806.13 * 4.98%* Hmean 32 3032.74 ( 0.00%) 3039.54 ( 0.22%) Hmean 64 2514.25 ( 0.00%) 2498.96 * -0.61%* Hmean 128 1778.49 ( 0.00%) 1746.05 * -1.82%* Note that this is somewhat specific to XFS and ext4 shows no performance difference as it does not rely on kworkers in the same way. No major problem was observed running other workloads on different machines although not all tests have completed yet. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200128154006.GD3466@techsingularity.net Signed-off-by: Ingo Molnar <mingo@kernel.org> |
H A D | fair.c | diff 8b4e74cc Wed Dec 01 07:34:50 MST 2021 Vincent Donnefort <vincent.donnefort@arm.com> sched/fair: Fix detection of per-CPU kthreads waking a task select_idle_sibling() has a special case for tasks woken up by a per-CPU kthread, where the selected CPU is the previous one. However, the current condition for this exit path is incomplete. A task can wake up from an interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A such scenario would spuriously trigger the special case described above. Also, a recent change made the idle task like a regular per-CPU kthread, hence making that situation more likely to happen (is_per_cpu_kthread(swapper) being true now). Checking for task context makes sure select_idle_sibling() will not interpret a wake up from any other context as a wake up by a per-CPU kthread. Fixes: 52262ee567ad ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com diff 52262ee5 Tue Jan 28 08:40:06 MST 2020 Mel Gorman <mgorman@techsingularity.net> sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression The following XFS commit: 8ab39f11d974 ("xfs: prevent CIL push holdoff in log recovery") changed the logic from using bound workqueues to using unbound workqueues. Functionally this makes sense but it was observed at the time that the dbench performance dropped quite a lot and CPU migrations were increased. The current pattern of the task migration is straight-forward. With XFS, an IO issuer delegates work to xlog_cil_push_work ()on an unbound kworker. This runs on a nearby CPU and on completion, dbench wakes up on its old CPU as it is still idle and no migration occurs. dbench then queues the real IO on the blk_mq_requeue_work() work item which runs on a bound kworker which is forced to run on the same CPU as dbench. When IO completes, the bound kworker wakes dbench but as the kworker is a bound but, real task, the CPU is not considered idle and dbench gets migrated by select_idle_sibling() to a new CPU. dbench may ping-pong between two CPUs for a while but ultimately it starts a round-robin of all CPUs sharing the same LLC. High-frequency migration on each IO completion has poor performance overall. It has negative implications both in commication costs and power management. mpstat confirmed that at low thread counts that all CPUs sharing an LLC has low level of activity. Note that even if the CIL patch was reverted, there still would be migrations but the impact is less noticeable. It turns out that individually the scheduler, XFS, blk-mq and workqueues all made sensible decisions but in combination, the overall effect was sub-optimal. This patch special cases the IO issue/completion pattern and allows a bound kworker waker and a task wakee to stack on the same CPU if there is a strong chance they are directly related. The expectation is that the kworker is likely going back to sleep shortly. This is not guaranteed as the IO could be queued asynchronously but there is a very strong relationship between the task and kworker in this case that would justify stacking on the same CPU instead of migrating. There should be few concerns about kworker starvation given that the special casing is only when the kworker is the waker. DBench on XFS MMTests config: io-dbench4-async modified to run on a fresh XFS filesystem UMA machine with 8 cores sharing LLC 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack Amean 1 22.63 ( 0.00%) 20.54 * 9.23%* Amean 2 25.56 ( 0.00%) 23.40 * 8.44%* Amean 4 28.63 ( 0.00%) 27.85 * 2.70%* Amean 8 37.66 ( 0.00%) 37.68 ( -0.05%) Amean 64 469.47 ( 0.00%) 468.26 ( 0.26%) Stddev 1 1.00 ( 0.00%) 0.72 ( 28.12%) Stddev 2 1.62 ( 0.00%) 1.97 ( -21.54%) Stddev 4 2.53 ( 0.00%) 3.58 ( -41.19%) Stddev 8 5.30 ( 0.00%) 5.20 ( 1.92%) Stddev 64 86.36 ( 0.00%) 94.53 ( -9.46%) NUMA machine, 48 CPUs total, 24 CPUs share cache 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Amean 1 58.69 ( 0.00%) 30.21 * 48.53%* Amean 2 60.90 ( 0.00%) 35.29 * 42.05%* Amean 4 66.77 ( 0.00%) 46.55 * 30.28%* Amean 8 81.41 ( 0.00%) 68.46 * 15.91%* Amean 16 113.29 ( 0.00%) 107.79 * 4.85%* Amean 32 199.10 ( 0.00%) 198.22 * 0.44%* Amean 64 478.99 ( 0.00%) 477.06 * 0.40%* Amean 128 1345.26 ( 0.00%) 1372.64 * -2.04%* Stddev 1 2.64 ( 0.00%) 4.17 ( -58.08%) Stddev 2 4.35 ( 0.00%) 5.38 ( -23.73%) Stddev 4 6.77 ( 0.00%) 6.56 ( 3.00%) Stddev 8 11.61 ( 0.00%) 10.91 ( 6.04%) Stddev 16 18.63 ( 0.00%) 19.19 ( -3.01%) Stddev 32 38.71 ( 0.00%) 38.30 ( 1.06%) Stddev 64 100.28 ( 0.00%) 91.24 ( 9.02%) Stddev 128 186.87 ( 0.00%) 160.34 ( 14.20%) Dbench has been modified to report the time to complete a single "load file". This is a more meaningful metric for dbench that a throughput metric as the benchmark makes many different system calls that are not throughput-related Patch shows a 9.23% and 48.53% reduction in the time to process a load file with the difference partially explained by the number of CPUs sharing a LLC. In a separate run, task migrations were almost eliminated by the patch for low client counts. In case people have issue with the metric used for the benchmark, this is a comparison of the throughputs as reported by dbench on the NUMA machine. dbench4 Throughput (misleading but traditional) 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Hmean 1 321.41 ( 0.00%) 617.82 * 92.22%* Hmean 2 622.87 ( 0.00%) 1066.80 * 71.27%* Hmean 4 1134.56 ( 0.00%) 1623.74 * 43.12%* Hmean 8 1869.96 ( 0.00%) 2212.67 * 18.33%* Hmean 16 2673.11 ( 0.00%) 2806.13 * 4.98%* Hmean 32 3032.74 ( 0.00%) 3039.54 ( 0.22%) Hmean 64 2514.25 ( 0.00%) 2498.96 * -0.61%* Hmean 128 1778.49 ( 0.00%) 1746.05 * -1.82%* Note that this is somewhat specific to XFS and ext4 shows no performance difference as it does not rely on kworkers in the same way. No major problem was observed running other workloads on different machines although not all tests have completed yet. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200128154006.GD3466@techsingularity.net Signed-off-by: Ingo Molnar <mingo@kernel.org> diff 8b4e74cc Wed Dec 01 07:34:50 MST 2021 Vincent Donnefort <vincent.donnefort@arm.com> sched/fair: Fix detection of per-CPU kthreads waking a task select_idle_sibling() has a special case for tasks woken up by a per-CPU kthread, where the selected CPU is the previous one. However, the current condition for this exit path is incomplete. A task can wake up from an interrupt context (e.g. hrtimer), while a per-CPU kthread is running. A such scenario would spuriously trigger the special case described above. Also, a recent change made the idle task like a regular per-CPU kthread, hence making that situation more likely to happen (is_per_cpu_kthread(swapper) being true now). Checking for task context makes sure select_idle_sibling() will not interpret a wake up from any other context as a wake up by a per-CPU kthread. Fixes: 52262ee567ad ("sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression") Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lore.kernel.org/r/20211201143450.479472-1-vincent.donnefort@arm.com diff 52262ee5 Tue Jan 28 08:40:06 MST 2020 Mel Gorman <mgorman@techsingularity.net> sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression The following XFS commit: 8ab39f11d974 ("xfs: prevent CIL push holdoff in log recovery") changed the logic from using bound workqueues to using unbound workqueues. Functionally this makes sense but it was observed at the time that the dbench performance dropped quite a lot and CPU migrations were increased. The current pattern of the task migration is straight-forward. With XFS, an IO issuer delegates work to xlog_cil_push_work ()on an unbound kworker. This runs on a nearby CPU and on completion, dbench wakes up on its old CPU as it is still idle and no migration occurs. dbench then queues the real IO on the blk_mq_requeue_work() work item which runs on a bound kworker which is forced to run on the same CPU as dbench. When IO completes, the bound kworker wakes dbench but as the kworker is a bound but, real task, the CPU is not considered idle and dbench gets migrated by select_idle_sibling() to a new CPU. dbench may ping-pong between two CPUs for a while but ultimately it starts a round-robin of all CPUs sharing the same LLC. High-frequency migration on each IO completion has poor performance overall. It has negative implications both in commication costs and power management. mpstat confirmed that at low thread counts that all CPUs sharing an LLC has low level of activity. Note that even if the CIL patch was reverted, there still would be migrations but the impact is less noticeable. It turns out that individually the scheduler, XFS, blk-mq and workqueues all made sensible decisions but in combination, the overall effect was sub-optimal. This patch special cases the IO issue/completion pattern and allows a bound kworker waker and a task wakee to stack on the same CPU if there is a strong chance they are directly related. The expectation is that the kworker is likely going back to sleep shortly. This is not guaranteed as the IO could be queued asynchronously but there is a very strong relationship between the task and kworker in this case that would justify stacking on the same CPU instead of migrating. There should be few concerns about kworker starvation given that the special casing is only when the kworker is the waker. DBench on XFS MMTests config: io-dbench4-async modified to run on a fresh XFS filesystem UMA machine with 8 cores sharing LLC 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack Amean 1 22.63 ( 0.00%) 20.54 * 9.23%* Amean 2 25.56 ( 0.00%) 23.40 * 8.44%* Amean 4 28.63 ( 0.00%) 27.85 * 2.70%* Amean 8 37.66 ( 0.00%) 37.68 ( -0.05%) Amean 64 469.47 ( 0.00%) 468.26 ( 0.26%) Stddev 1 1.00 ( 0.00%) 0.72 ( 28.12%) Stddev 2 1.62 ( 0.00%) 1.97 ( -21.54%) Stddev 4 2.53 ( 0.00%) 3.58 ( -41.19%) Stddev 8 5.30 ( 0.00%) 5.20 ( 1.92%) Stddev 64 86.36 ( 0.00%) 94.53 ( -9.46%) NUMA machine, 48 CPUs total, 24 CPUs share cache 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Amean 1 58.69 ( 0.00%) 30.21 * 48.53%* Amean 2 60.90 ( 0.00%) 35.29 * 42.05%* Amean 4 66.77 ( 0.00%) 46.55 * 30.28%* Amean 8 81.41 ( 0.00%) 68.46 * 15.91%* Amean 16 113.29 ( 0.00%) 107.79 * 4.85%* Amean 32 199.10 ( 0.00%) 198.22 * 0.44%* Amean 64 478.99 ( 0.00%) 477.06 * 0.40%* Amean 128 1345.26 ( 0.00%) 1372.64 * -2.04%* Stddev 1 2.64 ( 0.00%) 4.17 ( -58.08%) Stddev 2 4.35 ( 0.00%) 5.38 ( -23.73%) Stddev 4 6.77 ( 0.00%) 6.56 ( 3.00%) Stddev 8 11.61 ( 0.00%) 10.91 ( 6.04%) Stddev 16 18.63 ( 0.00%) 19.19 ( -3.01%) Stddev 32 38.71 ( 0.00%) 38.30 ( 1.06%) Stddev 64 100.28 ( 0.00%) 91.24 ( 9.02%) Stddev 128 186.87 ( 0.00%) 160.34 ( 14.20%) Dbench has been modified to report the time to complete a single "load file". This is a more meaningful metric for dbench that a throughput metric as the benchmark makes many different system calls that are not throughput-related Patch shows a 9.23% and 48.53% reduction in the time to process a load file with the difference partially explained by the number of CPUs sharing a LLC. In a separate run, task migrations were almost eliminated by the patch for low client counts. In case people have issue with the metric used for the benchmark, this is a comparison of the throughputs as reported by dbench on the NUMA machine. dbench4 Throughput (misleading but traditional) 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Hmean 1 321.41 ( 0.00%) 617.82 * 92.22%* Hmean 2 622.87 ( 0.00%) 1066.80 * 71.27%* Hmean 4 1134.56 ( 0.00%) 1623.74 * 43.12%* Hmean 8 1869.96 ( 0.00%) 2212.67 * 18.33%* Hmean 16 2673.11 ( 0.00%) 2806.13 * 4.98%* Hmean 32 3032.74 ( 0.00%) 3039.54 ( 0.22%) Hmean 64 2514.25 ( 0.00%) 2498.96 * -0.61%* Hmean 128 1778.49 ( 0.00%) 1746.05 * -1.82%* Note that this is somewhat specific to XFS and ext4 shows no performance difference as it does not rely on kworkers in the same way. No major problem was observed running other workloads on different machines although not all tests have completed yet. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200128154006.GD3466@techsingularity.net Signed-off-by: Ingo Molnar <mingo@kernel.org> |
H A D | core.c | diff 52262ee5 Tue Jan 28 08:40:06 MST 2020 Mel Gorman <mgorman@techsingularity.net> sched/fair: Allow a per-CPU kthread waking a task to stack on the same CPU, to fix XFS performance regression The following XFS commit: 8ab39f11d974 ("xfs: prevent CIL push holdoff in log recovery") changed the logic from using bound workqueues to using unbound workqueues. Functionally this makes sense but it was observed at the time that the dbench performance dropped quite a lot and CPU migrations were increased. The current pattern of the task migration is straight-forward. With XFS, an IO issuer delegates work to xlog_cil_push_work ()on an unbound kworker. This runs on a nearby CPU and on completion, dbench wakes up on its old CPU as it is still idle and no migration occurs. dbench then queues the real IO on the blk_mq_requeue_work() work item which runs on a bound kworker which is forced to run on the same CPU as dbench. When IO completes, the bound kworker wakes dbench but as the kworker is a bound but, real task, the CPU is not considered idle and dbench gets migrated by select_idle_sibling() to a new CPU. dbench may ping-pong between two CPUs for a while but ultimately it starts a round-robin of all CPUs sharing the same LLC. High-frequency migration on each IO completion has poor performance overall. It has negative implications both in commication costs and power management. mpstat confirmed that at low thread counts that all CPUs sharing an LLC has low level of activity. Note that even if the CIL patch was reverted, there still would be migrations but the impact is less noticeable. It turns out that individually the scheduler, XFS, blk-mq and workqueues all made sensible decisions but in combination, the overall effect was sub-optimal. This patch special cases the IO issue/completion pattern and allows a bound kworker waker and a task wakee to stack on the same CPU if there is a strong chance they are directly related. The expectation is that the kworker is likely going back to sleep shortly. This is not guaranteed as the IO could be queued asynchronously but there is a very strong relationship between the task and kworker in this case that would justify stacking on the same CPU instead of migrating. There should be few concerns about kworker starvation given that the special casing is only when the kworker is the waker. DBench on XFS MMTests config: io-dbench4-async modified to run on a fresh XFS filesystem UMA machine with 8 cores sharing LLC 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack Amean 1 22.63 ( 0.00%) 20.54 * 9.23%* Amean 2 25.56 ( 0.00%) 23.40 * 8.44%* Amean 4 28.63 ( 0.00%) 27.85 * 2.70%* Amean 8 37.66 ( 0.00%) 37.68 ( -0.05%) Amean 64 469.47 ( 0.00%) 468.26 ( 0.26%) Stddev 1 1.00 ( 0.00%) 0.72 ( 28.12%) Stddev 2 1.62 ( 0.00%) 1.97 ( -21.54%) Stddev 4 2.53 ( 0.00%) 3.58 ( -41.19%) Stddev 8 5.30 ( 0.00%) 5.20 ( 1.92%) Stddev 64 86.36 ( 0.00%) 94.53 ( -9.46%) NUMA machine, 48 CPUs total, 24 CPUs share cache 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Amean 1 58.69 ( 0.00%) 30.21 * 48.53%* Amean 2 60.90 ( 0.00%) 35.29 * 42.05%* Amean 4 66.77 ( 0.00%) 46.55 * 30.28%* Amean 8 81.41 ( 0.00%) 68.46 * 15.91%* Amean 16 113.29 ( 0.00%) 107.79 * 4.85%* Amean 32 199.10 ( 0.00%) 198.22 * 0.44%* Amean 64 478.99 ( 0.00%) 477.06 * 0.40%* Amean 128 1345.26 ( 0.00%) 1372.64 * -2.04%* Stddev 1 2.64 ( 0.00%) 4.17 ( -58.08%) Stddev 2 4.35 ( 0.00%) 5.38 ( -23.73%) Stddev 4 6.77 ( 0.00%) 6.56 ( 3.00%) Stddev 8 11.61 ( 0.00%) 10.91 ( 6.04%) Stddev 16 18.63 ( 0.00%) 19.19 ( -3.01%) Stddev 32 38.71 ( 0.00%) 38.30 ( 1.06%) Stddev 64 100.28 ( 0.00%) 91.24 ( 9.02%) Stddev 128 186.87 ( 0.00%) 160.34 ( 14.20%) Dbench has been modified to report the time to complete a single "load file". This is a more meaningful metric for dbench that a throughput metric as the benchmark makes many different system calls that are not throughput-related Patch shows a 9.23% and 48.53% reduction in the time to process a load file with the difference partially explained by the number of CPUs sharing a LLC. In a separate run, task migrations were almost eliminated by the patch for low client counts. In case people have issue with the metric used for the benchmark, this is a comparison of the throughputs as reported by dbench on the NUMA machine. dbench4 Throughput (misleading but traditional) 5.5.0-rc7 5.5.0-rc7 tipsched-20200124 kworkerstack-v1r2 Hmean 1 321.41 ( 0.00%) 617.82 * 92.22%* Hmean 2 622.87 ( 0.00%) 1066.80 * 71.27%* Hmean 4 1134.56 ( 0.00%) 1623.74 * 43.12%* Hmean 8 1869.96 ( 0.00%) 2212.67 * 18.33%* Hmean 16 2673.11 ( 0.00%) 2806.13 * 4.98%* Hmean 32 3032.74 ( 0.00%) 3039.54 ( 0.22%) Hmean 64 2514.25 ( 0.00%) 2498.96 * -0.61%* Hmean 128 1778.49 ( 0.00%) 1746.05 * -1.82%* Note that this is somewhat specific to XFS and ext4 shows no performance difference as it does not rely on kworkers in the same way. No major problem was observed running other workloads on different machines although not all tests have completed yet. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200128154006.GD3466@techsingularity.net Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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