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dyster

Member

Registered: 2019-12-09

Posts: 4

[SOLVED] /home is way slower than root directory; both on the same SSD

When I run the

time sh -c "dd if=/dev/zero of=test.bin bs=1M count=1000; sync"

command in my home directory, I get about 6 MB/S speed. However, running the same command in root directory, gives about 3 GB/S. I find this strange as both of these directories, even though on different partitions, share the same SSD.

Here's my `/etc/fstab` for reference:

UUID=01e6e674-a700-45f7-a932-04cad1e9af11	/         	btrfs     	rw,relatime,ssd,space_cache,subvolid=5,subvol=/	0 0

# /dev/nvme0n1p1
UUID=D1B5-D77B      	/efi      	vfat      	rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro	0 2

# /dev/nvme0n1p3
UUID=8189af98-8ad1-4353-88e8-6ee6a01dc0fc	none      	swap      	defaults  	0 0

# /dev/nvme0n1p4
UUID=8bc03ec3-281f-4945-934b-b43a03d8e7a7	/home      	btrfs      	rw,auto,nouser,sync,exec  	0 0

I'd appreciate any help.

Last edited by dyster (2020-04-22 15:58:50)

loqs

Member

Registered: 2014-03-06

Posts: 19,078

Re: [SOLVED] /home is way slower than root directory; both on the same SSD

If you drop sync from the options string used for /home is the result the same?

WorMzy

Administrator

From: Scotland

Registered: 2010-06-16

Posts: 13,654

Website

Re: [SOLVED] /home is way slower than root directory; both on the same SSD

According to the docs, sync is ignored by btrfs anyway:

       The following options apply to any filesystem that is being mounted (but not every filesystem actually  honors
       them – e.g., the sync option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):

'man 5 btrfs' also makes no mention of the sync option.

---

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loqs

Member

Registered: 2014-03-06

Posts: 19,078

Re: [SOLVED] /home is way slower than root directory; both on the same SSD

Perhaps https://github.com/torvalds/linux/blob/ … per.c#L705 is undocumented?

dyster

Member

Registered: 2019-12-09

Posts: 4

Re: [SOLVED] /home is way slower than root directory; both on the same SSD

Actually, removing sync improved it to around 1.8 GB/S.

Thank you loqs!