From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELvFsapHyWVpY8s/+n/wEoi0BH4wjJMQImgvtcvRFRdrDEt8oPJdCU5UA97MOALlGyNlm5RM ARC-Seal: i=1; a=rsa-sha256; t=1520945645; cv=none; d=google.com; s=arc-20160816; b=Yk6NptNpD+K3p92r55UE4grPzVc1NPUWhcQ+RizoQlSmYXXHtnIbJ/SDjNNAJnpPx0 zWwJh7oV3rhWu3ip0rVCKXtQ466Gh8ou2aUNmh0N5Pqft7aaqIAnWc7W8CzbHPaSag1p ip224+5AoGwfPowIXIkF2JJhHA2x9aNYAWXYAd3jXVs7+wLlczHybGhY90gxISEotOes rCgCLroy3KXFv/o2HbaafgMqqarAFZ8nquFYtVXZJS40dfcwqHkLeU2vuvSFcUjLS4cd aMWSh2SmYpuOvAUlj/lkGoB3h8cbGyZZpEbQAbu5rAw0KBgePy7G7OgRsCGB07YkP4AU QjEA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:date:subject:cc:to:from:arc-authentication-results; bh=FMskqqMvqhMbBZ5SZr6ez4Uh8ya5QU0oFGUL8Dwgtvc=; b=zZPnNOqYsI4NYhDfWhtDRKzharwUbATpLV+KVpRkX0t6hOkhK0nHJ1Uf6n7tZ2tXjA SZfiUVNTAfW5ZEY9jKYs+lrLWZ720ondKaEQDO/8qbffqvllZHNL9u77Hn8OiqNfFUWM j8P+/IyQQyRIk9NrUFYaL9GVRWTXqUwdijs9txwZInjKLm1u5+NxICvqJNLqm7QQC3Ms iRqDMVL2UyFbID8oopGDE0ROdWPfQ/H22eTagoLWotEptlC45ZVJNxOzp8S7KacfgG+z RA4h7VoSnU1+gHywyyDNudC9soWv7g1iTklLEpjwMcmYUS0KfZQq3fgGBSZMGk91UOL0 jQEw== ARC-Authentication-Results: i=1; mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Authentication-Results: mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com From: Ravi Bangoria To: mhiramat@kernel.org, oleg@redhat.com, peterz@infradead.org, srikar@linux.vnet.ibm.com Cc: acme@kernel.org, ananth@linux.vnet.ibm.com, akpm@linux-foundation.org, alexander.shishkin@linux.intel.com, alexis.berlemont@gmail.com, corbet@lwn.net, dan.j.williams@intel.com, gregkh@linuxfoundation.org, huawei.libin@huawei.com, hughd@google.com, jack@suse.cz, jglisse@redhat.com, jolsa@redhat.com, kan.liang@intel.com, kirill.shutemov@linux.intel.com, kjlx@templeofstupid.com, kstewart@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, milian.wolff@kdab.com, mingo@redhat.com, namhyung@kernel.org, naveen.n.rao@linux.vnet.ibm.com, pc@us.ibm.com, pombredanne@nexb.com, rostedt@goodmis.org, tglx@linutronix.de, tmricht@linux.vnet.ibm.com, willy@infradead.org, yao.jin@linux.intel.com, fengguang.wu@intel.com, Ravi Bangoria Subject: [PATCH 0/8] trace_uprobe: Support SDT markers having reference count (semaphore) Date: Tue, 13 Mar 2018 18:25:55 +0530 X-Mailer: git-send-email 2.14.3 X-TM-AS-GCONF: 00 x-cbid: 18031312-0008-0000-0000-000004DBFABC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18031312-0009-0000-0000-00001E6F2D61 Message-Id: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-13_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803130153 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594827101403620100?= X-GMAIL-MSGID: =?utf-8?q?1594827101403620100?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Userspace Statically Defined Tracepoints[1] are dtrace style markers inside userspace applications. These markers are added by developer at important places in the code. Each marker source expands to a single nop instruction in the compiled code but there may be additional overhead for computing the marker arguments which expands to couple of instructions. In case the overhead is more, execution of it can be omitted by runtime if() condition when no one is tracing on the marker: if (reference_counter > 0) { Execute marker instructions; } Default value of reference counter is 0. Tracer has to increment the reference counter before tracing on a marker and decrement it when done with the tracing. Currently, perf tool has limited supports for SDT markers. I.e. it can not trace markers surrounded by reference counter. Also, it's not easy to add reference counter logic in userspace tool like perf, so basic idea for this patchset is to add reference counter logic in the trace_uprobe infrastructure. Ex,[2] # cat tick.c ... for (i = 0; i < 100; i++) { DTRACE_PROBE1(tick, loop1, i); if (TICK_LOOP2_ENABLED()) { DTRACE_PROBE1(tick, loop2, i); } printf("hi: %d\n", i); sleep(1); } ... Here tick:loop1 is marker without reference counter where as tick:loop2 is surrounded by reference counter condition. # perf buildid-cache --add /tmp/tick # perf probe sdt_tick:loop1 # perf probe sdt_tick:loop2 # perf stat -e sdt_tick:loop1,sdt_tick:loop2 -- /tmp/tick hi: 0 hi: 1 hi: 2 ^C Performance counter stats for '/tmp/tick': 3 sdt_tick:loop1 0 sdt_tick:loop2 2.747086086 seconds time elapsed Perf failed to record data for tick:loop2. Same experiment with this patch series: # ./perf buildid-cache --add /tmp/tick # ./perf probe sdt_tick:loop2 # ./perf stat -e sdt_tick:loop2 /tmp/tick hi: 0 hi: 1 hi: 2 ^C Performance counter stats for '/tmp/tick': 3 sdt_tick:loop2 2.561851452 seconds time elapsed [1] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation [2] https://github.com/iovisor/bcc/issues/327#issuecomment-200576506 [3] https://lkml.org/lkml/2017/12/6/976 Note: 'reference counter' is called as 'semaphore' in original Dtrace (or Systemtap, bcc and even in ELF) documentation and code. But the term 'semaphore' is misleading in this context. This is just a counter used to hold number of tracers tracing on a marker. This is not really used for any synchronization. So we are referring it as 'reference counter' in kernel / perf code. RFC series can be found at: https://lkml.org/lkml/2018/2/28/76 Ravi Bangoria (8): Uprobe: Export vaddr <-> offset conversion functions mm: Prefix vma_ to vaddr_to_offset() and offset_to_vaddr() Uprobe: Rename map_info to uprobe_map_info Uprobe: Export uprobe_map_info along with uprobe_{build/free}_map_info() trace_uprobe: Support SDT markers having reference count (semaphore) trace_uprobe/sdt: Fix multiple update of same reference counter perf probe: Support SDT markers having reference counter (semaphore) trace_uprobe/sdt: Document about reference counter Documentation/trace/uprobetracer.txt | 16 +- include/linux/mm.h | 12 ++ include/linux/uprobes.h | 11 ++ kernel/events/uprobes.c | 62 ++++---- kernel/trace/trace.c | 2 +- kernel/trace/trace_uprobe.c | 273 ++++++++++++++++++++++++++++++++++- tools/perf/util/probe-event.c | 21 ++- tools/perf/util/probe-event.h | 1 + tools/perf/util/probe-file.c | 22 ++- tools/perf/util/symbol-elf.c | 10 ++ tools/perf/util/symbol.h | 1 + 11 files changed, 382 insertions(+), 49 deletions(-) -- 1.8.3.1