1869525066
Exclude patterns can be used by reference backends to skip over blocks
of references that are uninteresting to the caller. Reference backends
do not have to wire up support for them, and all callers are expected to
behave as if the backend didn't support them. In fact, the only backend
that supports exclude patterns right now is the "packed" backend.
Exclude patterns can be quite an important performance optimization in
repositories that have loads of references. The patterns are set up in
case "transfer.hideRefs" and friends are configured during a fetch, so
handling these patterns becomes important once there are lots of hidden
refs in a served repository.
Now that we have properly re-seekable reftable iterators we can also
wire up support for these patterns in the "reftable" backend. Doing so
is conceptually simple: once we hit a reference whose prefix matches the
current exclude pattern we re-seek the iterator to the first reference
that doesn't match the pattern anymore. This schema only works for
trivial patterns that do not have any globbing characters in them, but
this restriction also applies do the "packed" backend.
This makes t1419 work with the "reftable" backend with some slight
modifications. Of course it also speeds up listing of references with
hidden refs. The following benchmark prints one reference with 1 million
hidden references:
Benchmark 1: HEAD~
Time (mean ± σ): 93.3 ms ± 2.1 ms [User: 90.3 ms, System: 2.5 ms]
Range (min … max): 89.8 ms … 97.2 ms 33 runs
Benchmark 2: HEAD
Time (mean ± σ): 4.2 ms ± 0.6 ms [User: 2.2 ms, System: 1.8 ms]
Range (min … max): 3.1 ms … 8.1 ms 765 runs
Summary
HEAD ran
22.15 ± 3.19 times faster than HEAD~
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
121 lines
3.1 KiB
C
121 lines
3.1 KiB
C
#include "git-compat-util.h"
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#include "trace2/tr2_tgt.h"
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#include "trace2/tr2_tls.h"
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#include "trace2/tr2_ctr.h"
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/*
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* A global counter block to aggregrate values from the partial sums
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* from each thread.
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*/
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static struct tr2_counter_block final_counter_block; /* access under tr2tls_mutex */
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/*
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* Define metadata for each global counter.
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*
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* This array must match the "enum trace2_counter_id" and the values
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* in "struct tr2_counter_block.counter[*]".
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*/
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static struct tr2_counter_metadata tr2_counter_metadata[TRACE2_NUMBER_OF_COUNTERS] = {
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[TRACE2_COUNTER_ID_TEST1] = {
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.category = "test",
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.name = "test1",
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.want_per_thread_events = 0,
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},
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[TRACE2_COUNTER_ID_TEST2] = {
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.category = "test",
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.name = "test2",
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.want_per_thread_events = 1,
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},
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[TRACE2_COUNTER_ID_PACKED_REFS_JUMPS] = {
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.category = "packed-refs",
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.name = "jumps_made",
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.want_per_thread_events = 0,
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},
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[TRACE2_COUNTER_ID_REFTABLE_RESEEKS] = {
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.category = "reftable",
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.name = "reseeks_made",
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.want_per_thread_events = 0,
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},
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[TRACE2_COUNTER_ID_FSYNC_WRITEOUT_ONLY] = {
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.category = "fsync",
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.name = "writeout-only",
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.want_per_thread_events = 0,
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},
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[TRACE2_COUNTER_ID_FSYNC_HARDWARE_FLUSH] = {
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.category = "fsync",
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.name = "hardware-flush",
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.want_per_thread_events = 0,
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},
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/* Add additional metadata before here. */
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};
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void tr2_counter_increment(enum trace2_counter_id cid, uint64_t value)
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{
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struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
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struct tr2_counter *c = &ctx->counter_block.counter[cid];
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c->value += value;
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ctx->used_any_counter = 1;
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if (tr2_counter_metadata[cid].want_per_thread_events)
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ctx->used_any_per_thread_counter = 1;
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}
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void tr2_update_final_counters(void)
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{
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struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
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enum trace2_counter_id cid;
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if (!ctx->used_any_counter)
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return;
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/*
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* Access `final_counter_block` requires holding `tr2tls_mutex`.
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* We assume that our caller is holding the lock.
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*/
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for (cid = 0; cid < TRACE2_NUMBER_OF_COUNTERS; cid++) {
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struct tr2_counter *c_final = &final_counter_block.counter[cid];
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const struct tr2_counter *c = &ctx->counter_block.counter[cid];
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c_final->value += c->value;
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}
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}
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void tr2_emit_per_thread_counters(tr2_tgt_evt_counter_t *fn_apply)
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{
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struct tr2tls_thread_ctx *ctx = tr2tls_get_self();
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enum trace2_counter_id cid;
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if (!ctx->used_any_per_thread_counter)
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return;
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/*
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* For each counter, if the counter wants per-thread events
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* and this thread used it (the value is non-zero), emit it.
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*/
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for (cid = 0; cid < TRACE2_NUMBER_OF_COUNTERS; cid++)
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if (tr2_counter_metadata[cid].want_per_thread_events &&
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ctx->counter_block.counter[cid].value)
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fn_apply(&tr2_counter_metadata[cid],
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&ctx->counter_block.counter[cid],
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0);
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}
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void tr2_emit_final_counters(tr2_tgt_evt_counter_t *fn_apply)
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{
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enum trace2_counter_id cid;
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/*
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* Access `final_counter_block` requires holding `tr2tls_mutex`.
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* We assume that our caller is holding the lock.
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*/
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for (cid = 0; cid < TRACE2_NUMBER_OF_COUNTERS; cid++)
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if (final_counter_block.counter[cid].value)
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fn_apply(&tr2_counter_metadata[cid],
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&final_counter_block.counter[cid],
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1);
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}
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