From: Sasha Levin <sashal@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
Dexuan Cui <decui@microsoft.com>, Ming Lei <ming.lei@redhat.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>
Subject: Re: [PATCH AUTOSEL 5.15 20/29] block: reduce kblockd_mod_delayed_work_on() CPU consumption
Date: Tue, 21 Dec 2021 12:58:00 -0500 [thread overview]
Message-ID: <YcIVqFOrxbG8sqXK@sashalap> (raw)
In-Reply-To: <ad76826e-73b2-b2f0-3cd4-8481645a6568@kernel.dk>
On Tue, Dec 21, 2021 at 08:36:33AM -0700, Jens Axboe wrote:
>On 12/21/21 8:35 AM, Michael Kelley (LINUX) wrote:
>> From: Sasha Levin <sashal@kernel.org> Sent: Monday, December 20, 2021 5:58 PM
>>>
>>> From: Jens Axboe <axboe@kernel.dk>
>>>
>>> [ Upstream commit cb2ac2912a9ca7d3d26291c511939a41361d2d83 ]
>>>
>>> Dexuan reports that he's seeing spikes of very heavy CPU utilization when
>>> running 24 disks and using the 'none' scheduler. This happens off the
>>> sched restart path, because SCSI requires the queue to be restarted async,
>>> and hence we're hammering on mod_delayed_work_on() to ensure that the work
>>> item gets run appropriately.
>>>
>>> Avoid hammering on the timer and just use queue_work_on() if no delay
>>> has been specified.
>>>
>>> Reported-and-tested-by: Dexuan Cui <decui@microsoft.com>
>>> Link: https://lore.kernel.org/linux-block/BYAPR21MB1270C598ED214C0490F47400BF719@BYAPR21MB1270.namprd21.prod.outlook.com/
>>> Reviewed-by: Ming Lei <ming.lei@redhat.com>
>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>>> ---
>>> block/blk-core.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/block/blk-core.c b/block/blk-core.c
>>> index c2d912d0c976c..a728434fcff87 100644
>>> --- a/block/blk-core.c
>>> +++ b/block/blk-core.c
>>> @@ -1625,6 +1625,8 @@ EXPORT_SYMBOL(kblockd_schedule_work);
>>> int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork,
>>> unsigned long delay)
>>> {
>>> + if (!delay)
>>> + return queue_work_on(cpu, kblockd_workqueue, &dwork->work);
>>> return mod_delayed_work_on(cpu, kblockd_workqueue, dwork, delay);
>>> }
>>> EXPORT_SYMBOL(kblockd_mod_delayed_work_on);
>>> --
>>> 2.34.1
>>
>> Sasha -- there are reports of this patch causing performance problems.
>> See
>> https://lore.kernel.org/lkml/1639853092.524jxfaem2.none@localhost/. I
>> would suggest *not* backporting it to any of the stable branches until
>> the issues are fully sorted out.
>
>Both this and the revert were backported. Which arguably doesn't make a
>lot of sense, but at least it's consistent and won't cause any issues...
The logic behind it is that it makes it easy for both us as well as
everyone else to annotate why a certain patch might be "missing" from
the trees - in this case because it was reverted.
It looks dumb now, but it saves a lot of time as well as mitigates the
risk of it being picked up again at some point in the future.
--
Thanks,
Sasha
next prev parent reply other threads:[~2021-12-21 17:58 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-21 1:57 [PATCH AUTOSEL 5.15 01/29] ARM: dts: imx6qp-prtwd3: update RGMII delays for sja1105 switch Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 02/29] ARM: dts: ls1021a-tsn: " Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 03/29] ARM: rockchip: Use memcpy_toio instead of memcpy on smp bring-up Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 04/29] mac80211: fix TCP performance on mesh interface Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 05/29] mac80211: set up the fwd_skb->dev for mesh forwarding Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 06/29] mac80211: fix a memory leak where sta_info is not freed Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 07/29] nl80211: reset regdom when reloading regdb Sasha Levin
2021-12-25 18:23 ` Sedat Dilek
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 08/29] iwlwifi: fix LED dependencies Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 09/29] phonet: refcount leak in pep_sock_accep Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 10/29] net: usb: qmi_wwan: add Telit 0x1070 composition Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 11/29] dmaengine: ti: k3-udma: Fix smatch warnings Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 12/29] net: bcmgenet: Fix NULL vs IS_ERR() checking Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 13/29] net: ethernet: ti: add missing of_node_put before return Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 14/29] scsi: pm8001: Fix phys_to_virt() usage on dma_addr_t Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 15/29] mac80211: Fix the size used for building probe request Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 16/29] mac80211: update channel context before station state Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 17/29] mac80211: do drv_reconfig_complete() before restarting all Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 18/29] drm/amd/display: Reset DMCUB before HW init Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 19/29] drm/amdgpu: correct the wrong cached state for GMC on PICASSO Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 20/29] block: reduce kblockd_mod_delayed_work_on() CPU consumption Sasha Levin
2021-12-21 15:35 ` Michael Kelley (LINUX)
2021-12-21 15:36 ` Jens Axboe
2021-12-21 17:58 ` Sasha Levin [this message]
2021-12-21 18:11 ` Jens Axboe
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 21/29] net: usb: lan78xx: add Allied Telesis AT29M2-AF Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 22/29] virtio_net: fix rx_drops stat for small pkts Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 23/29] bpf: Make 32->64 bounds propagation slightly more robust Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 24/29] riscv: dts: sifive unmatched: Name gpio lines Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 25/29] riscv: dts: sifive unmatched: Expose the board ID eeprom Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 26/29] riscv: dts: sifive unmatched: Expose the PMIC sub-functions Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 27/29] riscv: dts: sifive unmatched: Fix regulator for board rev3 Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 28/29] riscv: dts: sifive unmatched: Link the tmp451 with its power supply Sasha Levin
2021-12-21 1:57 ` [PATCH AUTOSEL 5.15 29/29] Revert "block: reduce kblockd_mod_delayed_work_on() CPU consumption" Sasha Levin
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