Originally posted by timofonic
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Trying Out & Benchmarking Bcachefs On Linux 6.7
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Kent has made a response to these benchmarks: https://www.patreon.com/posts/note-on-phoronix-92281382
EDIT: In this response, he gets different results. He also says:
"I suspect a lot of [the performance issues shown on Phoronix] might be from having CONFIG_BCACHEFS_DEBUG_TRANSACTIONS on by default."Last edited by Mitch; 04 November 2023, 01:16 PM.
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Originally posted by Mitch View PostKent has made a response to these benchmarks: https://www.patreon.com/posts/note-on-phoronix-92281382Default mkfs options for all three filesystems.I suspect a lot of this might be from having CONFIG_BCACHEFS_DEBUG_TRANSACTIONS on by default.
To the people saying BCachefs is likely not optimized, Kent spent a lot of time optimizing the FS. He had an argument with the kernel devs, because he had a custom JIT-like thing, to unpack some data structure, because it would make some part 5% faster (making some pages WX, which the kernel team didn't like). IIRC they found a different approach that didn't impact performance much. Kent does absolutely care about performance. And I'm sure he's at least a bit surprised BCachefs gets destroyed in these benches.
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Originally posted by Mathias View Post
I don't understand. Did Michael enable DEBUG_TRANSACTIONS or is that a general reason why BCachefs may be slower?
To the people saying BCachefs is likely not optimized, Kent spent a lot of time optimizing the FS. He had an argument with the kernel devs, because he had a custom JIT-like thing, to unpack some data structure, because it would make some part 5% faster (making some pages WX, which the kernel team didn't like). IIRC they found a different approach that didn't impact performance much. Kent does absolutely care about performance. And I'm sure he's at least a bit surprised BCachefs gets destroyed in these benches.
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Originally posted by Mathias View Post
I don't understand. Did Michael enable DEBUG_TRANSACTIONS or is that a general reason why BCachefs may be slower?
To the people saying BCachefs is likely not optimized, Kent spent a lot of time optimizing the FS. He had an argument with the kernel devs, because he had a custom JIT-like thing, to unpack some data structure, because it would make some part 5% faster (making some pages WX, which the kernel team didn't like). IIRC they found a different approach that didn't impact performance much. Kent does absolutely care about performance. And I'm sure he's at least a bit surprised BCachefs gets destroyed in these benches.
Something is way off with phoronix's setup. In my testing Bcachefs comes out faster than btrfs and both are quite a bit faster than Phoronix's numbers.
Oh, i think a lot of why the phoronix numbers were so low. It is because CONFIG_BCACHEFS_DEBUG_TRANSACTIONS is on by default. It is a brilliant idea for how we can make all our btree_trans objects accessable for debugfs without them being on a single contended list.
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Originally posted by Hans Bull View PostSo was DEBUG_TRANSACTIONS on nor not?
Code:+config BCACHEFS_DEBUG_TRANSACTIONS + bool "bcachefs runtime info" + depends on BCACHEFS_FS + default y + help + This makes the list of running btree transactions available in debugfs. + + This is a highly useful debugging feature but does add a small amount of overhead.
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Originally posted by Mathias View Post
I don't understand. Did Michael enable DEBUG_TRANSACTIONS or is that a general reason why BCachefs may be slower?
To the people saying BCachefs is likely not optimized, Kent spent a lot of time optimizing the FS. He had an argument with the kernel devs, because he had a custom JIT-like thing, to unpack some data structure, because it would make some part 5% faster (making some pages WX, which the kernel team didn't like). IIRC they found a different approach that didn't impact performance much. Kent does absolutely care about performance. And I'm sure he's at least a bit surprised BCachefs gets destroyed in these benches.
He said in chatroom:
no, nothing i haven't sent out yet includes performance improvements
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