Karthik Nayak
654567cf1b
The struct `reftable_addition` is used to modify a given stack, as such, it also includes a `struct reftable_flock` used to obtain the lock to the list file. While the scope of the field lies within this struct, it doesn't allow for optimizations to be made on `struct reftable_stack` itself. Move the field to `struct reftable_stack`, allowing us to make a simple optimization around avoiding a stack reload when we have already obtained a lock. While this is currently possible in the write path, the write path also contains multiple branches to reads which only work on top of `struct reftable_stack`, and we would miss the optimization in such paths. Since the lock is now shared across all additions on the same stack, a second `reftable_addition` that fails to acquire the already held lock would still call `reftable_addition_close()`, which will release the `stack->list_lock` which is still held by the first addition. To avoid this, add a new bit field `locked` to `reftable_addition` that tracks whether a particular addition is the one holding the lock, and only release it in that case. Add a unit test to validate this behavior. While here, remove an unused header file from 'reftable/stack.h'. Signed-off-by: Karthik Nayak <karthik.188@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
47 lines
937 B
C
47 lines
937 B
C
/*
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* Copyright 2020 Google LLC
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*
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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 STACK_H
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#define STACK_H
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#include "system.h"
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#include "reftable-stack.h"
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struct reftable_stack {
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struct stat list_st;
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char *list_file;
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int list_fd;
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/*
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* Set while an addition holds the stack locked. Used by
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* stack_uptodate() to skip reload checks while locked.
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*/
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struct reftable_flock list_lock;
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char *reftable_dir;
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struct reftable_stack_options opts;
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struct reftable_table **tables;
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size_t tables_len;
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struct reftable_merged_table *merged;
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struct reftable_compaction_stats stats;
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};
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int read_lines(const char *filename, char ***lines);
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struct segment {
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size_t start, end;
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uint64_t bytes;
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};
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struct segment suggest_compaction_segment(uint64_t *sizes, size_t n,
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uint8_t factor);
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#endif
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