Re: Rocksdb compaction and OSD timeout

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Hey Konstantin,

forget to mention - indeed clusters having 4K bluestore min alloc size are more likely to be exposed to the issue. The key point is the difference between bluestore and bluefs allocation sizes. The issue likely to pop-up when user and DB data are collocated but different allocation units are in use. As a result allocator needs to locate properly aligned chunks for BlueFS among a bunch of inappropriate misaligned chunks. Which might be ineffective in the current implementation and cause the slowdown.



On 12/09/2023 15:47, Konstantin Shalygin wrote:
Hi Igor,

On 12 Sep 2023, at 15:28, Igor Fedotov <igor.fedotov@xxxxxxxx> wrote:

Default hybrid allocator (as well as AVL one it's based on) could take dramatically long time to allocate pretty large (hundreds of MBs) 64K-aligned chunks for BlueFS. At the original cluster it was exposed as 20-30 sec OSD stalls.
For the chunks, this mean bluestore min alloc size?
This cluster was deployed pre Pacific (64k) and not redeployed to Pacific default (4k)?

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