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Mon, 29 Dec 2025 17:41:17 -0800 (PST) Message-ID: <17b6ed66-6427-4098-8574-ac780cc1103b@gmail.com> Date: Tue, 30 Dec 2025 09:41:12 +0800 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: make periodic dynamic reclaim the default for data To: Boris Burkov Cc: kernel-team@fb.com, linux-btrfs@vger.kernel.org References: <52b863849f0dd63b3d25a29c8a830a09c748d86b.1752605888.git.boris@bur.io> <18e6a584-b6fb-47f9-b526-4e97798052a2@gmail.com> Content-Language: en-US From: Sun Yangkai In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit > Please let me know if I can assist you with that, or if you do have a > reproducer I could also look at. I just come with a ... thing I found and I have no idea why it happened. I've wrote a script to show the 10 least used block groups(used_space is just calculated from length and used_pct, so please just ignore them) and before periodic reclaim, I got: Searching for the 10 least used DATA block groups... vaddr length used_pct used_space -------------------------------------------------------- 6353387388928 1024MiB 5% 51MiB 6354461130752 1024MiB 30% 307MiB 6295292084224 1024MiB 80% 819MiB 6056900427776 1024MiB 89% 911MiB 4620552634368 1024MiB 97% 993MiB 6050457976832 1024MiB 98% 1003MiB 6122398679040 1024MiB 98% 1003MiB 6270596022272 1024MiB 98% 1003MiB 6350166163456 1024MiB 98% 1003MiB 383347851264 1024MiB 99% 1013MiB And unallocated space is 3GiB so with dynamic periodic reclaim, the first two block groups will be reclaimed: [12月28 21:47] [ T357] BTRFS info (device sda): relocating block group 6353387388928 flags data [ +0.262467] [ T357] BTRFS info (device sda): found 1970 extents, stage: move data extents [ +1.334556] [ T357] BTRFS info (device sda): found 1966 extents, stage: update data pointers [ +0.618457] [ T357] BTRFS info (device sda): relocating block group 6354461130752 flags data [ +1.009694] [ T357] BTRFS info (device sda): found 166 extents, stage: move data extents [ +0.388070] [ T357] BTRFS info (device sda): found 166 extents, stage: update data pointers And after the reclaim I got: Searching for the 10 least used DATA block groups... vaddr length used_pct used_space -------------------------------------------------------- 6355534872576 1024MiB 6% 61MiB 6356608614400 1024MiB 16% 163MiB 6295292084224 1024MiB 80% 819MiB 4620552634368 1024MiB 97% 993MiB 6050457976832 1024MiB 98% 1003MiB 6270596022272 1024MiB 98% 1003MiB 3782605471744 1024MiB 99% 1013MiB 4549685673984 1024MiB 99% 1013MiB 5882820034560 1024MiB 99% 1013MiB 5909764243456 1024MiB 99% 1013MiB These two block groups could be merged into existing chunks, but I have no idea why that didn't happen. But when I run btrfs balance start -dvrange=6355534872576..6355534872576 /mnt It can be merged and free some unallocated space. So I think the periodic reclaim has a different behavior with manually balance? Thanks, Sun YangKai