Date: Sun, 22 Oct 2017 20:22:24 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r324869 - in head/sys: cddl/dev/sdt kern sys Message-ID: <201710222022.v9MKMOjX043073@repo.freebsd.org>
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Author: mjg Date: Sun Oct 22 20:22:23 2017 New Revision: 324869 URL: https://svnweb.freebsd.org/changeset/base/324869 Log: sdt: make all sdt probe sites test one variable This saves on cache misses at the expense of a slight grow of .text. Note this is a bandaid for lack of hotpatching. Discussed with: markj Modified: head/sys/cddl/dev/sdt/sdt.c head/sys/kern/kern_sdt.c head/sys/sys/sdt.h Modified: head/sys/cddl/dev/sdt/sdt.c ============================================================================== --- head/sys/cddl/dev/sdt/sdt.c Sun Oct 22 20:22:11 2017 (r324868) +++ head/sys/cddl/dev/sdt/sdt.c Sun Oct 22 20:22:23 2017 (r324869) @@ -76,6 +76,8 @@ static void sdt_kld_unload_try(void *, struct linker_f static MALLOC_DEFINE(M_SDT, "SDT", "DTrace SDT providers"); +static int sdt_probes_enabled_count; + static dtrace_pattr_t sdt_attr = { { DTRACE_STABILITY_EVOLVING, DTRACE_STABILITY_EVOLVING, DTRACE_CLASS_COMMON }, { DTRACE_STABILITY_PRIVATE, DTRACE_STABILITY_PRIVATE, DTRACE_CLASS_UNKNOWN }, @@ -208,6 +210,9 @@ sdt_enable(void *arg __unused, dtrace_id_t id, void *p probe->sdtp_lf->nenabled++; if (strcmp(probe->prov->name, "lockstat") == 0) lockstat_enabled++; + sdt_probes_enabled_count++; + if (sdt_probes_enabled_count == 1) + sdt_probes_enabled = true; } static void @@ -217,6 +222,9 @@ sdt_disable(void *arg __unused, dtrace_id_t id, void * KASSERT(probe->sdtp_lf->nenabled > 0, ("no probes enabled")); + sdt_probes_enabled_count--; + if (sdt_probes_enabled_count == 0) + sdt_probes_enabled = false; if (strcmp(probe->prov->name, "lockstat") == 0) lockstat_enabled--; probe->id = 0; Modified: head/sys/kern/kern_sdt.c ============================================================================== --- head/sys/kern/kern_sdt.c Sun Oct 22 20:22:11 2017 (r324868) +++ head/sys/kern/kern_sdt.c Sun Oct 22 20:22:23 2017 (r324869) @@ -37,6 +37,7 @@ SDT_PROVIDER_DEFINE(sdt); * dtrace_probe() when it loads. */ sdt_probe_func_t sdt_probe_func = sdt_probe_stub; +volatile bool __read_frequently sdt_probes_enabled; /* * This is a stub for probe calls in case kernel DTrace support isn't Modified: head/sys/sys/sdt.h ============================================================================== --- head/sys/sys/sdt.h Sun Oct 22 20:22:11 2017 (r324868) +++ head/sys/sys/sdt.h Sun Oct 22 20:22:23 2017 (r324869) @@ -80,6 +80,8 @@ #include <sys/cdefs.h> #include <sys/linker_set.h> +extern volatile bool sdt_probes_enabled; + #ifndef KDTRACE_HOOKS #define SDT_PROVIDER_DEFINE(prov) @@ -161,10 +163,12 @@ SET_DECLARE(sdt_argtypes_set, struct sdt_argtype); extern struct sdt_probe sdt_##prov##_##mod##_##func##_##name[1] #define SDT_PROBE(prov, mod, func, name, arg0, arg1, arg2, arg3, arg4) do { \ - if (__predict_false(sdt_##prov##_##mod##_##func##_##name->id)) \ + if (__predict_false(sdt_probes_enabled)) { \ + if (__predict_false(sdt_##prov##_##mod##_##func##_##name->id)) \ (*sdt_probe_func)(sdt_##prov##_##mod##_##func##_##name->id, \ (uintptr_t) arg0, (uintptr_t) arg1, (uintptr_t) arg2, \ (uintptr_t) arg3, (uintptr_t) arg4); \ + } \ } while (0) #define SDT_PROBE_ARGTYPE(prov, mod, func, name, num, type, xtype) \
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