svn commit: r289003 - vendor-sys/illumos/dist/uts/common/dtrace vendor-sys/illumos/dist/uts/common/sys vendor/illumos/dist/cmd/dtrace/test/tst/common/usdt
Mark Johnston
markj at FreeBSD.org
Thu Oct 8 04:29:41 UTC 2015
Author: markj
Date: Thu Oct 8 04:29:39 2015
New Revision: 289003
URL: https://svnweb.freebsd.org/changeset/base/289003
Log:
6271 dtrace caused excessive fork time
Author: Bryan Cantrill <bryan at joyent.com>
Reviewed by: Adam Leventhal <ahl at delphix.com>
Reviewed by: Dan McDonald <danmcd at omniti.com>
Reviewed by: Richard Lowe <richlowe at richlowe.net>
Approved by: Gordon Ross <gwr at nexenta.com>
illumos/illumos-gate at 7bd3c1d12d0c764e1517c3aca62c634409356764
Modified:
vendor-sys/illumos/dist/uts/common/dtrace/dtrace.c
vendor-sys/illumos/dist/uts/common/dtrace/fasttrap.c
vendor-sys/illumos/dist/uts/common/sys/dtrace.h
Changes in other areas also in this revision:
Added:
vendor/illumos/dist/cmd/dtrace/test/tst/common/usdt/tst.sameprovmulti.ksh
vendor/illumos/dist/cmd/dtrace/test/tst/common/usdt/tst.sameprovmulti.ksh.out
Modified: vendor-sys/illumos/dist/uts/common/dtrace/dtrace.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/dtrace/dtrace.c Thu Oct 8 03:28:15 2015 (r289002)
+++ vendor-sys/illumos/dist/uts/common/dtrace/dtrace.c Thu Oct 8 04:29:39 2015 (r289003)
@@ -14809,8 +14809,8 @@ dtrace_helper_provider_add(dof_helper_t
* Check to make sure this isn't a duplicate.
*/
for (i = 0; i < help->dthps_nprovs; i++) {
- if (dofhp->dofhp_dof ==
- help->dthps_provs[i]->dthp_prov.dofhp_dof)
+ if (dofhp->dofhp_addr ==
+ help->dthps_provs[i]->dthp_prov.dofhp_addr)
return (EALREADY);
}
@@ -15162,7 +15162,14 @@ dtrace_helper_slurp(dof_hdr_t *dof, dof_
dtrace_enabling_destroy(enab);
if (dhp != NULL && nprovs > 0) {
+ /*
+ * Now that this is in-kernel, we change the sense of the
+ * members: dofhp_dof denotes the in-kernel copy of the DOF
+ * and dofhp_addr denotes the address at user-level.
+ */
+ dhp->dofhp_addr = dhp->dofhp_dof;
dhp->dofhp_dof = (uint64_t)(uintptr_t)dof;
+
if (dtrace_helper_provider_add(dhp, gen) == 0) {
mutex_exit(&dtrace_lock);
dtrace_helper_provider_register(curproc, help, dhp);
Modified: vendor-sys/illumos/dist/uts/common/dtrace/fasttrap.c
==============================================================================
--- vendor-sys/illumos/dist/uts/common/dtrace/fasttrap.c Thu Oct 8 03:28:15 2015 (r289002)
+++ vendor-sys/illumos/dist/uts/common/dtrace/fasttrap.c Thu Oct 8 04:29:39 2015 (r289003)
@@ -1784,6 +1784,18 @@ fasttrap_meta_provide(void *arg, dtrace_
return (provider);
}
+/*
+ * We know a few things about our context here: we know that the probe being
+ * created doesn't already exist (DTrace won't load DOF at the same address
+ * twice, even if explicitly told to do so) and we know that we are
+ * single-threaded with respect to the meta provider machinery. Knowing that
+ * this is a new probe and that there is no way for us to race with another
+ * operation on this provider allows us an important optimization: we need not
+ * lookup a probe before adding it. Saving this lookup is important because
+ * this code is in the fork path for processes with USDT probes, and lookups
+ * here are potentially very expensive because of long hash conflicts on
+ * module, function and name (DTrace doesn't hash on provider name).
+ */
/*ARGSUSED*/
static void
fasttrap_meta_create_probe(void *arg, void *parg,
@@ -1820,19 +1832,6 @@ fasttrap_meta_create_probe(void *arg, vo
return;
}
- /*
- * Grab the creation lock to ensure consistency between calls to
- * dtrace_probe_lookup() and dtrace_probe_create() in the face of
- * other threads creating probes.
- */
- mutex_enter(&provider->ftp_cmtx);
-
- if (dtrace_probe_lookup(provider->ftp_provid, dhpb->dthpb_mod,
- dhpb->dthpb_func, dhpb->dthpb_name) != 0) {
- mutex_exit(&provider->ftp_cmtx);
- return;
- }
-
ntps = dhpb->dthpb_noffs + dhpb->dthpb_nenoffs;
ASSERT(ntps > 0);
@@ -1840,7 +1839,6 @@ fasttrap_meta_create_probe(void *arg, vo
if (fasttrap_total > fasttrap_max) {
atomic_add_32(&fasttrap_total, -ntps);
- mutex_exit(&provider->ftp_cmtx);
return;
}
@@ -1904,8 +1902,6 @@ fasttrap_meta_create_probe(void *arg, vo
*/
pp->ftp_id = dtrace_probe_create(provider->ftp_provid, dhpb->dthpb_mod,
dhpb->dthpb_func, dhpb->dthpb_name, FASTTRAP_OFFSET_AFRAMES, pp);
-
- mutex_exit(&provider->ftp_cmtx);
}
/*ARGSUSED*/
Modified: vendor-sys/illumos/dist/uts/common/sys/dtrace.h
==============================================================================
--- vendor-sys/illumos/dist/uts/common/sys/dtrace.h Thu Oct 8 03:28:15 2015 (r289002)
+++ vendor-sys/illumos/dist/uts/common/sys/dtrace.h Thu Oct 8 04:29:39 2015 (r289003)
@@ -2131,12 +2131,18 @@ extern void dtrace_probe(dtrace_id_t, ui
*
* 1.2.4 Caller's context
*
- * dtms_create_probe() is called from either ioctl() or module load context.
- * The DTrace framework is locked in such a way that meta providers may not
- * register or unregister. This means that the meta provider cannot call
- * dtrace_meta_register() or dtrace_meta_unregister(). However, the context is
- * such that the provider may (and is expected to) call provider-related
- * DTrace provider APIs including dtrace_probe_create().
+ * dtms_create_probe() is called from either ioctl() or module load context
+ * in the context of a newly-created provider (that is, a provider that
+ * is a result of a call to dtms_provide_pid()). The DTrace framework is
+ * locked in such a way that meta providers may not register or unregister,
+ * such that no other thread can call into a meta provider operation and that
+ * atomicity is assured with respect to meta provider operations across
+ * dtms_provide_pid() and subsequent calls to dtms_create_probe().
+ * The context is thus effectively single-threaded with respect to the meta
+ * provider, and that the meta provider cannot call dtrace_meta_register()
+ * or dtrace_meta_unregister(). However, the context is such that the
+ * provider may (and is expected to) call provider-related DTrace provider
+ * APIs including dtrace_probe_create().
*
* 1.3 void *dtms_provide_pid(void *arg, dtrace_meta_provider_t *mprov,
* pid_t pid)
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