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66ed011bf7
Both `writer_add_record()` and `reftable_writer_add_ref()` get executed
for every single ref record we're adding to the reftable writer. And as
both functions use a local buffer to write data, the allocations we have
to do here add up during larger transactions.
Refactor the code to use a scratch buffer part of the `reftable_writer`
itself such that we can reuse it. This signifcantly reduces the number
of allocations during large transactions, e.g. when migrating refs from
the "files" backend to the "reftable" backend. Before this change:
HEAP SUMMARY:
in use at exit: 80,048 bytes in 49 blocks
total heap usage: 5,032,171 allocs, 5,032,122 frees, 418,792,092 bytes allocated
After this change:
HEAP SUMMARY:
in use at exit: 80,048 bytes in 49 blocks
total heap usage: 3,025,864 allocs, 3,025,815 frees, 372,746,291 bytes allocated
This also translate into a small speedup:
Benchmark 1: migrate files:reftable (refcount = 1000000, revision = HEAD~)
Time (mean ± σ): 827.2 ms ± 16.5 ms [User: 689.4 ms, System: 124.9 ms]
Range (min … max): 809.0 ms … 924.7 ms 50 runs
Benchmark 2: migrate files:reftable (refcount = 1000000, revision = HEAD)
Time (mean ± σ): 813.6 ms ± 11.6 ms [User: 679.0 ms, System: 123.4 ms]
Range (min … max): 786.7 ms … 833.5 ms 50 runs
Summary
migrate files:reftable (refcount = 1000000, revision = HEAD) ran
1.02 ± 0.02 times faster than migrate files:reftable (refcount = 1000000, revision = HEAD~)
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
53 lines
1.1 KiB
C
53 lines
1.1 KiB
C
/*
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Copyright 2020 Google LLC
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Use of this source code is governed by a BSD-style
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license that can be found in the LICENSE file or at
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https://developers.google.com/open-source/licenses/bsd
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*/
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#ifndef WRITER_H
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#define WRITER_H
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#include "basics.h"
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#include "block.h"
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#include "tree.h"
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#include "reftable-writer.h"
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struct reftable_writer {
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ssize_t (*write)(void *, const void *, size_t);
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int (*flush)(void *);
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void *write_arg;
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int pending_padding;
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struct reftable_buf last_key;
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struct reftable_buf buf;
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/* offset of next block to write. */
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uint64_t next;
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uint64_t min_update_index, max_update_index;
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struct reftable_write_options opts;
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/* memory buffer for writing */
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uint8_t *block;
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/* writer for the current section. NULL or points to
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* block_writer_data */
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struct block_writer *block_writer;
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struct block_writer block_writer_data;
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/* pending index records for the current section */
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struct reftable_index_record *index;
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size_t index_len;
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size_t index_cap;
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/*
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* tree for use with tsearch; used to populate the 'o' inverse OID
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* map */
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struct tree_node *obj_index_tree;
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struct reftable_stats stats;
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};
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#endif
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