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From: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
To: Pankaj Raghav <p.raghav@samsung.com>, David Sterba <dsterba@suse.com>
Cc: Josef Bacik <josef@toxicpanda.com>,
	"linux-btrfs@vger.kernel.org" <linux-btrfs@vger.kernel.org>,
	Luis Chamberlain <mcgrof@kernel.org>,
	Javier Gonzalez <javier.gonz@samsung.com>
Subject: Re: [PATCH 5/5] btrfs: zoned: make auto-reclaim less aggressive
Date: Wed, 23 Mar 2022 09:11:55 +0000	[thread overview]
Message-ID: <PH0PR04MB7416CD1BC88132E22790A1869B189@PH0PR04MB7416.namprd04.prod.outlook.com> (raw)
In-Reply-To: f4e4a70c-0349-fafa-8375-8c4177a3e260@samsung.com

On 23/03/2022 10:09, Pankaj Raghav wrote:
> Hi Johannes,
> 
> I tried this patchset and I am noticing a weird behaviour wrt the value
> of factor in btrfs_zoned_should_reclaim function.
> 
> Here is my setup in QEMU:
> size 12800M
> zoned=true,zoned.zone_capacity=128M,zoned.zone_size=128M
> 
> btrfs mkfs:
> mkfs.btrfs -d single -m single <znsdev>;  mount -t auto <znsdev>
> /mnt/real_scratch
> 
> I added a print statement in btrfs_zoned_should_reclaim to get the
> values for the factor, used and total params.
> 
> When I run the btrfs/237 xfstest, I am noticing the following values:
> [   54.829309] btrfs: factor: 4850 used: 19528679424, total: 402653184
> 
> The used > total, thereby making the factor greater than 100. This will
> force a reclaim even though the drive is almost empty:
> 
>   start: 0x000000000, len 0x040000, cap 0x040000, wptr 0x000078 reset:0
> non-seq:0, zcond: 2(oi) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000040000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000080000, len 0x040000, cap 0x040000, wptr 0x0001e0 reset:0
> non-seq:0, zcond: 2(oi) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x0000c0000, len 0x040000, cap 0x040000, wptr 0x000d80 reset:0
> non-seq:0, zcond: 2(oi) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000100000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000140000, len 0x040000, cap 0x040000, wptr 0x008520 reset:0
> non-seq:0, zcond: 2(oi) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000180000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x0001c0000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000200000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000240000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x000280000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
>   start: 0x0002c0000, len 0x040000, cap 0x040000, wptr 0x000000 reset:0
> non-seq:0, zcond: 1(em) [type: 2(SEQ_WRITE_REQUIRED)]
> .....
> .....
> 
> I am also noticing the same behaviour for ZNS drive with size 1280M:
> 
> [   86.276409] btrfs: factor: 350 used: 1409286144, total: 402653184
> 
> Is something going wrong with the calculation? Or am I missing something
> here?
> 

Apparently I'm either too dumb for basic maths, or 
btrfs_calc_available_free_space() doesn't give us the values we're expecting.

I'll recheck.

  reply	other threads:[~2022-03-23  9:12 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-21 16:14 [PATCH 0/5] btrfs: rework background block group relocation Johannes Thumshirn
2022-03-21 16:14 ` [PATCH 1/5] btrfs: make the bg_reclaim_threshold per-space info Johannes Thumshirn
2022-03-22 17:32   ` Josef Bacik
2022-03-22 17:34     ` Johannes Thumshirn
2022-03-21 16:14 ` [PATCH 2/5] btrfs: allow block group background reclaim for !zoned fs'es Johannes Thumshirn
2022-03-22 17:38   ` Josef Bacik
2022-03-22 17:40     ` Johannes Thumshirn
2022-03-21 16:14 ` [PATCH 3/5] btrfs: change the bg_reclaim_threshold valid region from 0 to 100 Johannes Thumshirn
2022-03-21 16:14 ` [PATCH 4/5] btrfs: make calc_available_free_space available outside of space-info Johannes Thumshirn
2022-03-22 17:34   ` Josef Bacik
2022-03-21 16:14 ` [PATCH 5/5] btrfs: zoned: make auto-reclaim less aggressive Johannes Thumshirn
2022-03-23  9:08   ` Pankaj Raghav
2022-03-23  9:11     ` Johannes Thumshirn [this message]
2022-03-23  9:14       ` Pankaj Raghav
2022-03-23 10:39         ` Johannes Thumshirn
2022-03-23 11:24           ` Pankaj Raghav
2022-03-23 11:52             ` Johannes Thumshirn
2022-03-23 19:37               ` Pankaj Raghav
2022-03-24  0:06               ` Damien Le Moal

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