Messages in this thread | | | Date | Sun, 12 Mar 2000 18:40:18 +0100 | From | Pavel Machek <> | Subject | Re: patch: reiserfs for 2.3.49 |
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Hi!
> It has long been an architectural weakness of ReiserFS that we allocate block > numbers to buffers as we need each buffer. We knew that we should cure this by > doing either pre-allocation of blocknrs as ext2 does (meaning allocate many > blocks at a time, and then keep them reserved for that file until file close), > or allocating block numbers on dirty buffer/page flush as XFS does. It is for > sure the case that our current practice of allocating blocks as we need new > buffers to write into is a bad architecture. Yura wrote some pre-allocation code > that improved our performance by as much as 4x in some benchmarks, but I > discouraged it because I prefer allocate on flush. This decision is hurting us > at the moment. Pre-allocation is much easier to code (and already written by > Yura for an older version), allocate on flush is the right answer long-term. > Zam has been working on allocate on flush for about 6 weeks, but it is not ready > yet. I think we will have Yura throw in his pre-allocation code
Does on-disk layout differ between no-prealloc, prealloc, and alloc-on-flush versions? Probably not. Then there's no problem getting no-prealloc into kernel first ASAP, then changing it to alloc-on-flush. Pavel
-- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents me at discuss@linmodems.org
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