Add a simple utility to detect profiling bias.

This commit is contained in:
David Goldblatt 2020-08-03 15:27:08 -07:00 committed by David Goldblatt
parent e032a1a1de
commit 81c2f841e5
4 changed files with 75 additions and 2 deletions

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@ -294,7 +294,8 @@ CPP_SRCS :=
TESTS_INTEGRATION_CPP :=
endif
TESTS_ANALYZE := $(srcroot)test/analyze/rand.c \
$(srcroot)test/analyze/sizes.c
$(srcroot)test/analyze/sizes.c \
$(srcroot)test/analyze/prof_bias.c
TESTS_STRESS := $(srcroot)test/stress/microbench.c \
$(srcroot)test/stress/fill_flush.c \
$(srcroot)test/stress/large_microbench.c \

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@ -43,6 +43,13 @@ extern size_t lg_prof_sample;
extern bool prof_booted;
/*
* A hook to mock out backtrace functionality. This can be handy, since it's
* otherwise difficult to guarantee that two allocations are reported as coming
* from the exact same stack trace in the presence of an optimizing compiler.
*/
extern void (* JET_MUTABLE prof_backtrace_hook)(prof_bt_t *bt);
/* Functions only accessed in prof_inlines.h */
prof_tdata_t *prof_tdata_init(tsd_t *tsd);
prof_tdata_t *prof_tdata_reinit(tsd_t *tsd, prof_tdata_t *tdata);

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@ -27,6 +27,8 @@
malloc_mutex_t prof_dump_filename_mtx;
bool prof_do_mock = false;
static uint64_t prof_dump_seq;
static uint64_t prof_dump_iseq;
static uint64_t prof_dump_mseq;
@ -267,11 +269,14 @@ prof_backtrace_impl(prof_bt_t *bt) {
}
#endif
void (* JET_MUTABLE prof_backtrace_hook)(prof_bt_t *bt) = &prof_backtrace_impl;
void
prof_backtrace(tsd_t *tsd, prof_bt_t *bt) {
cassert(config_prof);
pre_reentrancy(tsd, NULL);
prof_backtrace_impl(bt);
prof_backtrace_hook(bt);
post_reentrancy(tsd);
}

60
test/analyze/prof_bias.c Normal file
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@ -0,0 +1,60 @@
#include "test/jemalloc_test.h"
/*
* This is a helper utility, only meant to be run manually (and, for example,
* doesn't check for failures, try to skip execution in non-prof modes, etc.).
* It runs, allocates objects of two different sizes from the same stack trace,
* and exits.
*
* The idea is that some human operator will run it like:
* MALLOC_CONF="prof:true,prof_final:true" test/analyze/prof_bias
* and manually inspect the results.
*
* The results should be:
* jeprof --text test/analyze/prof_bias --inuse_space jeprof.<pid>.0.f.heap:
* around 1024 MB
* jeprof --text test/analyze/prof_bias --inuse_objects jeprof.<pid>.0.f.heap:
* around 33554448 = 16 + 32 * 1024 * 1024
*
* And, if prof_accum is on:
* jeprof --text test/analyze/prof_bias --alloc_space jeprof.<pid>.0.f.heap:
* around 2048 MB
* jeprof --text test/analyze/prof_bias --alloc_objects jeprof.<pid>.0.f.heap:
* around 67108896 = 2 * (16 + 32 * 1024 * 1024)
*/
static void
mock_backtrace(prof_bt_t *bt) {
bt->len = 4;
bt->vec[0] = (void *)0x111;
bt->vec[1] = (void *)0x222;
bt->vec[2] = (void *)0x333;
bt->vec[3] = (void *)0x444;
}
static void
do_allocs(size_t sz, size_t cnt, bool do_frees) {
for (size_t i = 0; i < cnt; i++) {
void *ptr = mallocx(sz, 0);
assert_ptr_not_null(ptr, "Unexpected mallocx failure");
if (do_frees) {
dallocx(ptr, 0);
}
}
}
int
main(void) {
size_t lg_prof_sample = 19;
int err = mallctl("prof.reset", NULL, NULL, (void *)&lg_prof_sample,
sizeof(lg_prof_sample));
assert(err == 0);
prof_backtrace_hook = &mock_backtrace;
do_allocs(16, 32 * 1024 * 1024, /* do_frees */ true);
do_allocs(32 * 1024* 1024, 16, /* do_frees */ true);
do_allocs(16, 32 * 1024 * 1024, /* do_frees */ false);
do_allocs(32 * 1024* 1024, 16, /* do_frees */ false);
return 0;
}