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greatroar 5141228e0c repository: Re-tune indexmap allocation strategy 
fd05037e1a changed the allocation batch
size from 256 to 128 under the assumption that an indexEntry is 60 bytes
on amd64, but it's 64: structs are padded out to a multiple of 8 for
alignment reasons. That means we'd waste no space in malloc even without
the batch allocation, at least on 64-bit machines. While that strategy
cuts the overallocation down dramatically for many small indexes, it also
seems to slow allocation down (Go 1.18, Linux, amd64, -benchtime=2s):

    name                   old time/op    new time/op    delta
    DecodeIndex-8             4.67s ± 5%     4.60s ± 1%      ~     (p=0.953 n=10+5)
    DecodeIndexParallel-8     4.67s ± 3%     4.60s ± 1%      ~     (p=0.953 n=10+5)
    IndexHasUnknown-8        37.8ns ± 8%    36.5ns ±14%      ~     (p=0.841 n=5+5)
    IndexHasKnown-8          38.5ns ±12%    37.7ns ±10%      ~     (p=0.968 n=5+5)
    IndexAlloc-8              615ms ±18%     607ms ± 1%      ~     (p=1.000 n=10+5)
    IndexAllocParallel-8      245ms ±11%     285ms ± 6%   +16.40%  (p=0.001 n=10+5)
    MasterIndexAlloc-8        286ms ± 9%     275ms ± 2%      ~     (p=1.000 n=10+5)
    LoadIndex/v1-8           27.0ms ± 4%    26.8ms ± 1%      ~     (p=0.690 n=5+5)
    LoadIndex/v2-8           22.4ms ± 1%    22.8ms ± 2%    +1.48%  (p=0.016 n=5+5)

    name                   old alloc/op   new alloc/op   delta
    IndexAlloc-8              446MB ± 0%     446MB ± 0%    -0.00%  (p=0.000 n=8+4)
    IndexAllocParallel-8      446MB ± 0%     446MB ± 0%    -0.00%  (p=0.008 n=8+5)
    MasterIndexAlloc-8        213MB ± 0%     159MB ± 0%   -25.47%  (p=0.000 n=10+5)

    name                   old allocs/op  new allocs/op  delta
    IndexAlloc-8               913k ± 0%     2632k ± 0%  +188.19%  (p=0.008 n=5+5)
    IndexAllocParallel-8       913k ± 0%     2632k ± 0%  +188.21%  (p=0.008 n=5+5)
    MasterIndexAlloc-8         318k ± 0%     1172k ± 0%  +267.86%  (p=0.008 n=5+5)

Instead, this patch sets a batch size of 4, which means no space is
wasted by malloc on 64-bit and very little on 32-bit. It still gets very
close to the savings from not allocating in batches, without requiring
special code for bits.UintSize==64. Benchmark results, again for
Linux/amd64:

    name                   old time/op    new time/op    delta
    DecodeIndex-8             4.67s ± 5%     4.83s ± 9%     ~     (p=0.315 n=10+10)
    DecodeIndexParallel-8     4.67s ± 3%     4.68s ± 4%     ~     (p=0.315 n=10+10)
    IndexHasUnknown-8        37.8ns ± 8%    44.5ns ±19%     ~     (p=0.095 n=5+5)
    IndexHasKnown-8          38.5ns ±12%    36.9ns ± 8%     ~     (p=0.690 n=5+5)
    IndexAlloc-8              615ms ±18%     628ms ±18%     ~     (p=0.218 n=10+10)
    IndexAllocParallel-8      245ms ±11%     262ms ± 9%   +7.02%  (p=0.043 n=10+10)
    MasterIndexAlloc-8        286ms ± 9%     287ms ±13%     ~     (p=1.000 n=10+10)
    LoadIndex/v1-8           27.0ms ± 4%    26.8ms ± 0%     ~     (p=1.000 n=5+5)
    LoadIndex/v2-8           22.4ms ± 1%    22.5ms ± 0%     ~     (p=0.056 n=5+5)

    name                   old alloc/op   new alloc/op   delta
    IndexAlloc-8              446MB ± 0%     446MB ± 0%     ~     (p=1.000 n=8+10)
    IndexAllocParallel-8      446MB ± 0%     446MB ± 0%   -0.00%  (p=0.000 n=8+8)
    MasterIndexAlloc-8        213MB ± 0%     160MB ± 0%  -25.02%  (p=0.000 n=10+9)

    name                   old allocs/op  new allocs/op  delta
    IndexAlloc-8               913k ± 0%     1333k ± 0%  +45.94%  (p=0.000 n=8+10)
    IndexAllocParallel-8       913k ± 0%     1333k ± 0%  +45.94%  (p=0.000 n=8+8)
    MasterIndexAlloc-8         318k ± 0%      525k ± 0%  +64.99%  (p=0.000 n=10+10)

The allocation method indexmap.newEntry has also been rewritten in a
form that is a few instructions shorter.
2022-05-11 21:22:14 +02:00
..
testdata Moves files 2017-07-23 14:19:13 +02:00
doc.go Moves files 2017-07-23 14:19:13 +02:00
index.go repository: Increase index size for repo version 2 2022-04-30 11:34:10 +02:00
index_parallel.go repository: Rename LoadAndDecrypt to LoadUnpacked 2022-03-28 22:09:49 +02:00
index_parallel_test.go repository: Add test for ForAllIndexes 2020-12-22 22:36:18 +01:00
index_test.go repository: test uncompressedLength field and index example 2022-04-30 11:34:10 +02:00
indexmap.go repository: Re-tune indexmap allocation strategy 2022-05-11 21:22:14 +02:00
indexmap_test.go repository: implement pack compression 2022-04-30 11:34:10 +02:00
key.go crypto: Use helpers for size calculations 2022-03-28 22:09:49 +02:00
master_index.go repository: Refactor index IDs collection 2022-04-30 19:14:21 +02:00
master_index_test.go repository: test uncompressedLength field and index example 2022-04-30 11:34:10 +02:00
packer_manager.go Simplify cache logic 2021-09-03 21:01:00 +02:00
packer_manager_test.go repository: implement pack compression 2022-04-30 11:34:10 +02:00
repack.go repository: Reduce repack workers to prevent deadlock 2022-04-23 11:28:18 +02:00
repack_test.go repository: run blackbox tests using old and new repo version 2022-04-30 11:34:10 +02:00
repository.go repository: Use existing method to collect pack ids 2022-04-30 19:14:21 +02:00
repository_internal_test.go Use "pack file" instead of "data file" (#2885) 2020-08-16 11:16:38 +02:00
repository_test.go repository: Test compressed blobs in StreamPack 2022-04-30 11:34:10 +02:00
testing.go repository: run blackbox tests using old and new repo version 2022-04-30 11:34:10 +02:00
worker_group.go defer close(ch) outside repository.RunWorkers 2020-10-14 15:50:16 +02:00