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SubjectRe: [PATCH] reiserfs: eliminate minimum window size for bitmap searching
Jeff Mahoney wrote:
> When a file system becomes fragmented (using MythTV, for example), the
> bigalloc window searching ends up causing huge performance problems. In
> a file system presented by a user experiencing this bug, the file system
> was 90% free, but no 32-block free windows existed on the entire file system.
> This causes the allocator to scan the entire file system for each 128k write
> before backing down to searching for individual blocks.

Question: Would it be better to take that performance hit once, then
cache the result for awhile? If we can't find enough consecutive space,
such space isn't likely to appear until a lot of space is freed or a
repacker is run.

> In the end, finding a contiguous window for all the blocks in a write is
> an advantageous special case, but one that can be found naturally when
> such a window exists anyway.

Hmm. Ok, I don't understand how this works, so I'll shut up.
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