1/*-------------------------------------------------------------------------
2 *
3 * jit.c
4 * Provider independent JIT infrastructure.
5 *
6 * Code related to loading JIT providers, redirecting calls into JIT providers
7 * and error handling. No code specific to a specific JIT implementation
8 * should end up here.
9 *
10 *
11 * Copyright (c) 2016-2019, PostgreSQL Global Development Group
12 *
13 * IDENTIFICATION
14 * src/backend/jit/jit.c
15 *
16 *-------------------------------------------------------------------------
17 */
18#include "postgres.h"
19
20
21#include <sys/types.h>
22#include <sys/stat.h>
23#include <unistd.h>
24
25
26#include "fmgr.h"
27#include "executor/execExpr.h"
28#include "jit/jit.h"
29#include "miscadmin.h"
30#include "utils/resowner_private.h"
31#include "utils/fmgrprotos.h"
32
33
34/* GUCs */
35bool jit_enabled = true;
36char *jit_provider = NULL;
37bool jit_debugging_support = false;
38bool jit_dump_bitcode = false;
39bool jit_expressions = true;
40bool jit_profiling_support = false;
41bool jit_tuple_deforming = true;
42double jit_above_cost = 100000;
43double jit_inline_above_cost = 500000;
44double jit_optimize_above_cost = 500000;
45
46static JitProviderCallbacks provider;
47static bool provider_successfully_loaded = false;
48static bool provider_failed_loading = false;
49
50
51static bool provider_init(void);
52static bool file_exists(const char *name);
53
54
55/*
56 * SQL level function returning whether JIT is available in the current
57 * backend. Will attempt to load JIT provider if necessary.
58 */
59Datum
60pg_jit_available(PG_FUNCTION_ARGS)
61{
62 PG_RETURN_BOOL(provider_init());
63}
64
65
66/*
67 * Return whether a JIT provider has successfully been loaded, caching the
68 * result.
69 */
70static bool
71provider_init(void)
72{
73 char path[MAXPGPATH];
74 JitProviderInit init;
75
76 /* don't even try to load if not enabled */
77 if (!jit_enabled)
78 return false;
79
80 /*
81 * Don't retry loading after failing - attempting to load JIT provider
82 * isn't cheap.
83 */
84 if (provider_failed_loading)
85 return false;
86 if (provider_successfully_loaded)
87 return true;
88
89 /*
90 * Check whether shared library exists. We do that check before actually
91 * attempting to load the shared library (via load_external_function()),
92 * because that'd error out in case the shlib isn't available.
93 */
94 snprintf(path, MAXPGPATH, "%s/%s%s", pkglib_path, jit_provider, DLSUFFIX);
95 elog(DEBUG1, "probing availability of JIT provider at %s", path);
96 if (!file_exists(path))
97 {
98 elog(DEBUG1,
99 "provider not available, disabling JIT for current session");
100 provider_failed_loading = true;
101 return false;
102 }
103
104 /*
105 * If loading functions fails, signal failure. We do so because
106 * load_external_function() might error out despite the above check if
107 * e.g. the library's dependencies aren't installed. We want to signal
108 * ERROR in that case, so the user is notified, but we don't want to
109 * continually retry.
110 */
111 provider_failed_loading = true;
112
113 /* and initialize */
114 init = (JitProviderInit)
115 load_external_function(path, "_PG_jit_provider_init", true, NULL);
116 init(&provider);
117
118 provider_successfully_loaded = true;
119 provider_failed_loading = false;
120
121 elog(DEBUG1, "successfully loaded JIT provider in current session");
122
123 return true;
124}
125
126/*
127 * Reset JIT provider's error handling. This'll be called after an error has
128 * been thrown and the main-loop has re-established control.
129 */
130void
131jit_reset_after_error(void)
132{
133 if (provider_successfully_loaded)
134 provider.reset_after_error();
135}
136
137/*
138 * Release resources required by one JIT context.
139 */
140void
141jit_release_context(JitContext *context)
142{
143 if (provider_successfully_loaded)
144 provider.release_context(context);
145
146 ResourceOwnerForgetJIT(context->resowner, PointerGetDatum(context));
147 pfree(context);
148}
149
150/*
151 * Ask provider to JIT compile an expression.
152 *
153 * Returns true if successful, false if not.
154 */
155bool
156jit_compile_expr(struct ExprState *state)
157{
158 /*
159 * We can easily create a one-off context for functions without an
160 * associated PlanState (and thus EState). But because there's no executor
161 * shutdown callback that could deallocate the created function, they'd
162 * live to the end of the transactions, where they'd be cleaned up by the
163 * resowner machinery. That can lead to a noticeable amount of memory
164 * usage, and worse, trigger some quadratic behaviour in gdb. Therefore,
165 * at least for now, don't create a JITed function in those circumstances.
166 */
167 if (!state->parent)
168 return false;
169
170 /* if no jitting should be performed at all */
171 if (!(state->parent->state->es_jit_flags & PGJIT_PERFORM))
172 return false;
173
174 /* or if expressions aren't JITed */
175 if (!(state->parent->state->es_jit_flags & PGJIT_EXPR))
176 return false;
177
178 /* this also takes !jit_enabled into account */
179 if (provider_init())
180 return provider.compile_expr(state);
181
182 return false;
183}
184
185/* Aggregate JIT instrumentation information */
186void
187InstrJitAgg(JitInstrumentation *dst, JitInstrumentation *add)
188{
189 dst->created_functions += add->created_functions;
190 INSTR_TIME_ADD(dst->generation_counter, add->generation_counter);
191 INSTR_TIME_ADD(dst->inlining_counter, add->inlining_counter);
192 INSTR_TIME_ADD(dst->optimization_counter, add->optimization_counter);
193 INSTR_TIME_ADD(dst->emission_counter, add->emission_counter);
194}
195
196static bool
197file_exists(const char *name)
198{
199 struct stat st;
200
201 AssertArg(name != NULL);
202
203 if (stat(name, &st) == 0)
204 return S_ISDIR(st.st_mode) ? false : true;
205 else if (!(errno == ENOENT || errno == ENOTDIR))
206 ereport(ERROR,
207 (errcode_for_file_access(),
208 errmsg("could not access file \"%s\": %m", name)));
209
210 return false;
211}
212