Hi all, Here's an RFCv2 of the near block allocation algorithm rework. The changes since the first rfc are primarily to clean out a bunch of unnecessary refactoring, further improvements/cleanups to the code and the addition of minlen support. While I ran some basic performance tests against the initial version as I was fleshing out the high level algorithm, this has mostly only seen functional testing since then. Hence this is still RFC until I've had a chance to do more thorough testing. The limited performance testing that I have run consists of a simple single-writer fs_mark test against the pre-fragmented metadump image provided by the user. A single threaded fs_mark writes in the range of 30-100 files/sec (150k sized files) on a baseline kernel and 550-800 files/sec with the updated allocator algorithm. The latter range is about the same as the result for both kernels against a newly created filesystem on the same system. More testing is certainly required, but I'd like to solicit high level design feedback before getting too far down the targeted testing path, including any thoughts on specific performance tests that might be worthwhile. The background and motivation for this change is described in the patch 2 commit log as well as in the original thread referenced in the rfcv1 cover letter. The original idea was to replace the current allocator with a single locality-enhanced cntbt lookup. This refines that idea to something that combines the cntbt and bnobt searches in a manner that is optimal for the size of the request (for example, a single fsb near alloc is a trivial bnobt lookup) and repeats the cntbt lookup to provide a bit more locality. While this is written as new code, this is really based on the existing allocation algorithm and rewritten in a way to facilitate reuse for the other allocation modes. The longer term objective beyond improving worst case near mode allocation behavior is to be able to reuse this code for all of the near, exact and size allocation modes. The latter bits will likely occur as follow on work. Note that this series should technically only consist of two patches. Patch 1 is a dependency fixup for the small allocation fallback. Patches 2 and 3 are artificially split into two to improve readability in patch form. Patch 2 adds the new mechanism and patch 3 changes the near allocation path to use it. Thoughts, reviews, flames appreciated. Brian rfcv2: - Dropped spurious initial refactoring. - Added minlen functionality. - Properly tied into near alloc path. - General refactoring and cleanups. rfcv1: https://marc.info/?l=linux-xfs&m=154479089914351&w=2 Brian Foster (3): xfs: refactor small allocation helper to skip cntbt attempt xfs: introduce generic extent allocation infrastructure xfs: use generic extent alloc mechanism for near mode allocs fs/xfs/libxfs/xfs_alloc.c | 928 +++++++++++++++++++------------------- fs/xfs/xfs_trace.h | 26 +- 2 files changed, 493 insertions(+), 461 deletions(-) -- 2.17.2
