* Weird delay introduced in v6.16-rc only, possible regression
@ 2025-06-29 21:45 Qu Wenruo
2025-07-01 16:30 ` Jens Axboe
0 siblings, 1 reply; 6+ messages in thread
From: Qu Wenruo @ 2025-06-29 21:45 UTC (permalink / raw)
To: linux-block@vger.kernel.org, LKML
Hi,
Recently I'm hitting a very weird delay when doing development inside a
x86_64 VM.
The dmesg shows the delay (10+ sec) between virtio blk and device-mapper:
[ 3.651377] virtio_blk virtio4: 10/0/0 default/read/poll queues
[ 3.653075] virtio_scsi virtio2: 10/0/0 default/read/poll queues
[ 3.670269] virtio_blk virtio4: [vda] 83886080 512-byte logical
blocks (42.9 GB/40.0 GiB)
[ 3.672096] scsi host6: Virtio SCSI HBA
[ 3.708452] vda: vda1 vda2
[ 3.711073] virtio_blk virtio5: 10/0/0 default/read/poll queues
[ 3.729879] virtio_blk virtio5: [vdb] 167772160 512-byte logical
blocks (85.9 GB/80.0 GiB)
[ 3.737535] virtio_blk virtio8: 10/0/0 default/read/poll queues
[ 3.747045] virtio_blk virtio8: [vdc] 83886080 512-byte logical
blocks (42.9 GB/40.0 GiB)
[ 17.453833] device-mapper: uevent: version 1.0.3
[ 17.455689] device-mapper: ioctl: 4.50.0-ioctl (2025-04-28)
initialised: dm-devel@lists.linux.dev
:: performing fsck on '/dev/os/root'
/dev/mapper/os-root: clean, 240299/1048576 files, 3372218/4194304 blocks
:: mounting '/dev/os/root' on real root
[ 17.871671] EXT4-fs (dm-0): mounted filesystem
00a85626-d289-4817-8183-ee828e221f76 r/w with ordered data mode. Quota
mode: none.
The VM is running kernel based on upstream commit 78f4e737a53e ("Merge
tag 'for-6.16/dm-fixes' of
git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm"),
with a lot of extra btrfs patches.
The v6.15 kernel from Archlinux is totally fine without any delay.
The v6.16-rc kernel may have some different configs, but the config is
used for a long long time, way before v6.15, so it looks like it's
something in the v6.16 cycle causing problems.
I can definitely do a bisection, but any clue would be appreciated.
Thanks,
Qu
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Weird delay introduced in v6.16-rc only, possible regression 2025-06-29 21:45 Weird delay introduced in v6.16-rc only, possible regression Qu Wenruo @ 2025-07-01 16:30 ` Jens Axboe 2025-07-01 22:07 ` Qu Wenruo 0 siblings, 1 reply; 6+ messages in thread From: Jens Axboe @ 2025-07-01 16:30 UTC (permalink / raw) To: Qu Wenruo, linux-block@vger.kernel.org, LKML On 6/29/25 3:45 PM, Qu Wenruo wrote: > Hi, > > Recently I'm hitting a very weird delay when doing development inside a x86_64 VM. > > The dmesg shows the delay (10+ sec) between virtio blk and device-mapper: > > [ 3.651377] virtio_blk virtio4: 10/0/0 default/read/poll queues > [ 3.653075] virtio_scsi virtio2: 10/0/0 default/read/poll queues > [ 3.670269] virtio_blk virtio4: [vda] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) > [ 3.672096] scsi host6: Virtio SCSI HBA > [ 3.708452] vda: vda1 vda2 > [ 3.711073] virtio_blk virtio5: 10/0/0 default/read/poll queues > [ 3.729879] virtio_blk virtio5: [vdb] 167772160 512-byte logical blocks (85.9 GB/80.0 GiB) > [ 3.737535] virtio_blk virtio8: 10/0/0 default/read/poll queues > [ 3.747045] virtio_blk virtio8: [vdc] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) > [ 17.453833] device-mapper: uevent: version 1.0.3 > [ 17.455689] device-mapper: ioctl: 4.50.0-ioctl (2025-04-28) initialised: dm-devel@lists.linux.dev > :: performing fsck on '/dev/os/root' > /dev/mapper/os-root: clean, 240299/1048576 files, 3372218/4194304 blocks > :: mounting '/dev/os/root' on real root > [ 17.871671] EXT4-fs (dm-0): mounted filesystem 00a85626-d289-4817-8183-ee828e221f76 r/w with ordered data mode. Quota mode: none. > > The VM is running kernel based on upstream commit 78f4e737a53e ("Merge tag 'for-6.16/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm"), with a lot of extra btrfs patches. > > > The v6.15 kernel from Archlinux is totally fine without any delay. > > The v6.16-rc kernel may have some different configs, but the config is used for a long long time, way before v6.15, so it looks like it's something in the v6.16 cycle causing problems. > > I can definitely do a bisection, but any clue would be appreciated. Probably a good idea to go ahead with a bisect to help pin it down. -- Jens Axboe ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Weird delay introduced in v6.16-rc only, possible regression 2025-07-01 16:30 ` Jens Axboe @ 2025-07-01 22:07 ` Qu Wenruo 2025-07-01 22:11 ` Jens Axboe 0 siblings, 1 reply; 6+ messages in thread From: Qu Wenruo @ 2025-07-01 22:07 UTC (permalink / raw) To: Jens Axboe, linux-block@vger.kernel.org, LKML 在 2025/7/2 02:00, Jens Axboe 写道: > On 6/29/25 3:45 PM, Qu Wenruo wrote: >> Hi, >> >> Recently I'm hitting a very weird delay when doing development inside a x86_64 VM. >> >> The dmesg shows the delay (10+ sec) between virtio blk and device-mapper: >> >> [ 3.651377] virtio_blk virtio4: 10/0/0 default/read/poll queues >> [ 3.653075] virtio_scsi virtio2: 10/0/0 default/read/poll queues >> [ 3.670269] virtio_blk virtio4: [vda] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) >> [ 3.672096] scsi host6: Virtio SCSI HBA >> [ 3.708452] vda: vda1 vda2 >> [ 3.711073] virtio_blk virtio5: 10/0/0 default/read/poll queues >> [ 3.729879] virtio_blk virtio5: [vdb] 167772160 512-byte logical blocks (85.9 GB/80.0 GiB) >> [ 3.737535] virtio_blk virtio8: 10/0/0 default/read/poll queues >> [ 3.747045] virtio_blk virtio8: [vdc] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) >> [ 17.453833] device-mapper: uevent: version 1.0.3 >> [ 17.455689] device-mapper: ioctl: 4.50.0-ioctl (2025-04-28) initialised: dm-devel@lists.linux.dev >> :: performing fsck on '/dev/os/root' >> /dev/mapper/os-root: clean, 240299/1048576 files, 3372218/4194304 blocks >> :: mounting '/dev/os/root' on real root >> [ 17.871671] EXT4-fs (dm-0): mounted filesystem 00a85626-d289-4817-8183-ee828e221f76 r/w with ordered data mode. Quota mode: none. >> >> The VM is running kernel based on upstream commit 78f4e737a53e ("Merge tag 'for-6.16/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm"), with a lot of extra btrfs patches. >> >> >> The v6.15 kernel from Archlinux is totally fine without any delay. >> >> The v6.16-rc kernel may have some different configs, but the config is used for a long long time, way before v6.15, so it looks like it's something in the v6.16 cycle causing problems. >> >> I can definitely do a bisection, but any clue would be appreciated. > > Probably a good idea to go ahead with a bisect to help pin it down. > BTW, a little more digging shows it's the `udevadm settle` causing the long delay in the initramfs. The rootfs is an ext4 on a LVM lv, so initramfs is required to mount the rootfs. So it may not be the block/dm layer causing the problem. Thanks, Qu ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Weird delay introduced in v6.16-rc only, possible regression 2025-07-01 22:07 ` Qu Wenruo @ 2025-07-01 22:11 ` Jens Axboe 2025-07-02 3:52 ` Qu Wenruo 0 siblings, 1 reply; 6+ messages in thread From: Jens Axboe @ 2025-07-01 22:11 UTC (permalink / raw) To: Qu Wenruo, linux-block@vger.kernel.org, LKML On 7/1/25 4:07 PM, Qu Wenruo wrote: > > > ? 2025/7/2 02:00, Jens Axboe ??: >> On 6/29/25 3:45 PM, Qu Wenruo wrote: >>> Hi, >>> >>> Recently I'm hitting a very weird delay when doing development inside a x86_64 VM. >>> >>> The dmesg shows the delay (10+ sec) between virtio blk and device-mapper: >>> >>> [ 3.651377] virtio_blk virtio4: 10/0/0 default/read/poll queues >>> [ 3.653075] virtio_scsi virtio2: 10/0/0 default/read/poll queues >>> [ 3.670269] virtio_blk virtio4: [vda] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) >>> [ 3.672096] scsi host6: Virtio SCSI HBA >>> [ 3.708452] vda: vda1 vda2 >>> [ 3.711073] virtio_blk virtio5: 10/0/0 default/read/poll queues >>> [ 3.729879] virtio_blk virtio5: [vdb] 167772160 512-byte logical blocks (85.9 GB/80.0 GiB) >>> [ 3.737535] virtio_blk virtio8: 10/0/0 default/read/poll queues >>> [ 3.747045] virtio_blk virtio8: [vdc] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) >>> [ 17.453833] device-mapper: uevent: version 1.0.3 >>> [ 17.455689] device-mapper: ioctl: 4.50.0-ioctl (2025-04-28) initialised: dm-devel@lists.linux.dev >>> :: performing fsck on '/dev/os/root' >>> /dev/mapper/os-root: clean, 240299/1048576 files, 3372218/4194304 blocks >>> :: mounting '/dev/os/root' on real root >>> [ 17.871671] EXT4-fs (dm-0): mounted filesystem 00a85626-d289-4817-8183-ee828e221f76 r/w with ordered data mode. Quota mode: none. >>> >>> The VM is running kernel based on upstream commit 78f4e737a53e ("Merge tag 'for-6.16/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm"), with a lot of extra btrfs patches. >>> >>> >>> The v6.15 kernel from Archlinux is totally fine without any delay. >>> >>> The v6.16-rc kernel may have some different configs, but the config is used for a long long time, way before v6.15, so it looks like it's something in the v6.16 cycle causing problems. >>> >>> I can definitely do a bisection, but any clue would be appreciated. >> >> Probably a good idea to go ahead with a bisect to help pin it down. >> > > BTW, a little more digging shows it's the `udevadm settle` causing the long delay in the initramfs. > > The rootfs is an ext4 on a LVM lv, so initramfs is required to mount the rootfs. > > So it may not be the block/dm layer causing the problem. Even the more reason to bisect it then, if we don't quite know why it's slow. -- Jens Axboe ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Weird delay introduced in v6.16-rc only, possible regression 2025-07-01 22:11 ` Jens Axboe @ 2025-07-02 3:52 ` Qu Wenruo 2025-07-02 4:14 ` Qu Wenruo 0 siblings, 1 reply; 6+ messages in thread From: Qu Wenruo @ 2025-07-02 3:52 UTC (permalink / raw) To: Jens Axboe, linux-block@vger.kernel.org, LKML 在 2025/7/2 07:41, Jens Axboe 写道: > On 7/1/25 4:07 PM, Qu Wenruo wrote: >> >> >> ? 2025/7/2 02:00, Jens Axboe ??: >>> On 6/29/25 3:45 PM, Qu Wenruo wrote: >>>> Hi, >>>> >>>> Recently I'm hitting a very weird delay when doing development inside a x86_64 VM. >>>> >>>> The dmesg shows the delay (10+ sec) between virtio blk and device-mapper: >>>> >>>> [ 3.651377] virtio_blk virtio4: 10/0/0 default/read/poll queues >>>> [ 3.653075] virtio_scsi virtio2: 10/0/0 default/read/poll queues >>>> [ 3.670269] virtio_blk virtio4: [vda] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) >>>> [ 3.672096] scsi host6: Virtio SCSI HBA >>>> [ 3.708452] vda: vda1 vda2 >>>> [ 3.711073] virtio_blk virtio5: 10/0/0 default/read/poll queues >>>> [ 3.729879] virtio_blk virtio5: [vdb] 167772160 512-byte logical blocks (85.9 GB/80.0 GiB) >>>> [ 3.737535] virtio_blk virtio8: 10/0/0 default/read/poll queues >>>> [ 3.747045] virtio_blk virtio8: [vdc] 83886080 512-byte logical blocks (42.9 GB/40.0 GiB) >>>> [ 17.453833] device-mapper: uevent: version 1.0.3 >>>> [ 17.455689] device-mapper: ioctl: 4.50.0-ioctl (2025-04-28) initialised: dm-devel@lists.linux.dev >>>> :: performing fsck on '/dev/os/root' >>>> /dev/mapper/os-root: clean, 240299/1048576 files, 3372218/4194304 blocks >>>> :: mounting '/dev/os/root' on real root >>>> [ 17.871671] EXT4-fs (dm-0): mounted filesystem 00a85626-d289-4817-8183-ee828e221f76 r/w with ordered data mode. Quota mode: none. >>>> >>>> The VM is running kernel based on upstream commit 78f4e737a53e ("Merge tag 'for-6.16/dm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm"), with a lot of extra btrfs patches. >>>> >>>> >>>> The v6.15 kernel from Archlinux is totally fine without any delay. >>>> >>>> The v6.16-rc kernel may have some different configs, but the config is used for a long long time, way before v6.15, so it looks like it's something in the v6.16 cycle causing problems. >>>> >>>> I can definitely do a bisection, but any clue would be appreciated. >>> >>> Probably a good idea to go ahead with a bisect to help pin it down. >>> >> >> BTW, a little more digging shows it's the `udevadm settle` causing the long delay in the initramfs. >> >> The rootfs is an ext4 on a LVM lv, so initramfs is required to mount the rootfs. >> >> So it may not be the block/dm layer causing the problem. > > Even the more reason to bisect it then, if we don't quite know why it's > slow. > It looks like my memory is blurry, I tried as old as v6.14 (v6.13 failed to compile using the latest gcc 15.1.1), all the same delay. Thus I believe it may be some missing kernel config causing the problem. Let me retry with the base Archlinux kernel config and see what's going wrong. Thanks, Qu ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Weird delay introduced in v6.16-rc only, possible regression 2025-07-02 3:52 ` Qu Wenruo @ 2025-07-02 4:14 ` Qu Wenruo 0 siblings, 0 replies; 6+ messages in thread From: Qu Wenruo @ 2025-07-02 4:14 UTC (permalink / raw) To: Jens Axboe, linux-block@vger.kernel.org, LKML 在 2025/7/2 13:22, Qu Wenruo 写道: > > > 在 2025/7/2 07:41, Jens Axboe 写道: >> On 7/1/25 4:07 PM, Qu Wenruo wrote: >>> >>> >>> ? 2025/7/2 02:00, Jens Axboe ??: >>>> On 6/29/25 3:45 PM, Qu Wenruo wrote: >>>>> Hi, >>>>> >>>>> Recently I'm hitting a very weird delay when doing development >>>>> inside a x86_64 VM. >>>>> >>>>> The dmesg shows the delay (10+ sec) between virtio blk and device- >>>>> mapper: >>>>> >>>>> [ 3.651377] virtio_blk virtio4: 10/0/0 default/read/poll queues >>>>> [ 3.653075] virtio_scsi virtio2: 10/0/0 default/read/poll queues >>>>> [ 3.670269] virtio_blk virtio4: [vda] 83886080 512-byte logical >>>>> blocks (42.9 GB/40.0 GiB) >>>>> [ 3.672096] scsi host6: Virtio SCSI HBA >>>>> [ 3.708452] vda: vda1 vda2 >>>>> [ 3.711073] virtio_blk virtio5: 10/0/0 default/read/poll queues >>>>> [ 3.729879] virtio_blk virtio5: [vdb] 167772160 512-byte logical >>>>> blocks (85.9 GB/80.0 GiB) >>>>> [ 3.737535] virtio_blk virtio8: 10/0/0 default/read/poll queues >>>>> [ 3.747045] virtio_blk virtio8: [vdc] 83886080 512-byte logical >>>>> blocks (42.9 GB/40.0 GiB) >>>>> [ 17.453833] device-mapper: uevent: version 1.0.3 >>>>> [ 17.455689] device-mapper: ioctl: 4.50.0-ioctl (2025-04-28) >>>>> initialised: dm-devel@lists.linux.dev >>>>> :: performing fsck on '/dev/os/root' >>>>> /dev/mapper/os-root: clean, 240299/1048576 files, 3372218/4194304 >>>>> blocks >>>>> :: mounting '/dev/os/root' on real root >>>>> [ 17.871671] EXT4-fs (dm-0): mounted filesystem 00a85626- >>>>> d289-4817-8183-ee828e221f76 r/w with ordered data mode. Quota mode: >>>>> none. >>>>> >>>>> The VM is running kernel based on upstream commit 78f4e737a53e >>>>> ("Merge tag 'for-6.16/dm-fixes' of git://git.kernel.org/pub/scm/ >>>>> linux/kernel/git/device-mapper/linux-dm"), with a lot of extra >>>>> btrfs patches. >>>>> >>>>> >>>>> The v6.15 kernel from Archlinux is totally fine without any delay. >>>>> >>>>> The v6.16-rc kernel may have some different configs, but the config >>>>> is used for a long long time, way before v6.15, so it looks like >>>>> it's something in the v6.16 cycle causing problems. >>>>> >>>>> I can definitely do a bisection, but any clue would be appreciated. >>>> >>>> Probably a good idea to go ahead with a bisect to help pin it down. >>>> >>> >>> BTW, a little more digging shows it's the `udevadm settle` causing >>> the long delay in the initramfs. >>> >>> The rootfs is an ext4 on a LVM lv, so initramfs is required to mount >>> the rootfs. >>> >>> So it may not be the block/dm layer causing the problem. >> >> Even the more reason to bisect it then, if we don't quite know why it's >> slow. >> > > It looks like my memory is blurry, I tried as old as v6.14 (v6.13 failed > to compile using the latest gcc 15.1.1), all the same delay. > > Thus I believe it may be some missing kernel config causing the problem. > > Let me retry with the base Archlinux kernel config and see what's going > wrong. Confirmed, with minimal change/trimming to the Archlinux kernel config, everything is back fine. So there must be some config being trimmed and causing the `udevadm settle` to wait for some sysfs interface that will never come up. Sorry for the noise, and thankfully it's not a kernel regression. Thanks, Qu > > Thanks, > Qu ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2025-07-02 4:14 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2025-06-29 21:45 Weird delay introduced in v6.16-rc only, possible regression Qu Wenruo 2025-07-01 16:30 ` Jens Axboe 2025-07-01 22:07 ` Qu Wenruo 2025-07-01 22:11 ` Jens Axboe 2025-07-02 3:52 ` Qu Wenruo 2025-07-02 4:14 ` Qu Wenruo
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