Re: [libvirt] Memory free in libvirt JNA

Hi Daniel, At Fri, 28 Sep 2012 22:34:13 +0800, Daniel Veillard wrote: Me too. So, no worries! ;) This effects mostly Strings. JNA takes the safe assumption that functions are returning "const char*"s because it can't distinguish a string (const char*) from a string (char*). See https://github.com/twall/jna/blob/master/www/FrequentlyAskedQuestions.md#... So, here is a list of methods of org.libvirt.jna.Libvirt which return a string (/probably/ a char*, not const char*) which need to be checked: virConnectBaselineCPU virConnectDomainXMLFromNative virConnectDomainXMLToNative virConnectFindStoragePoolSources virConnectGetCapabilities virConnectGetHostname virConnectGetType virConnectGetURI virDomainGetName virDomainGetOSType virDomainGetXMLDesc virDomainSnapshotGetXMLDesc virInterfaceGetMACString virInterfaceGetName virInterfaceGetXMLDesc virNWFilterGetName virNWFilterGetXMLDesc virNetworkGetBridgeName virNetworkGetName virNetworkGetXMLDesc virNodeDeviceGetName virNodeDeviceGetParent virNodeDeviceGetXMLDesc virSecretGetUsageID virSecretGetXMLDesc virStoragePoolGetName virStoragePoolGetXMLDesc virStorageVolGetKey virStorageVolGetName virStorageVolGetPath virStorageVolGetXMLDesc I tried valgrind, but it didn't produce any output. mtrace wasn't very helpful either. So, I just hacked this up: ,----[ memcheck.py ] | import gdb | | allocations = {} | | class AllocBreak(gdb.FinishBreakpoint): | def stop(self): | global allocations | | if self.return_value != None: | callstack = [] | frame = gdb.selected_frame() | | while frame: | name = frame.name() | func = frame.function() | sal = frame.find_sal() | | funcname = func.print_name if func else '?' | line = sal.line | filename = sal.symtab.filename if sal.symtab else '?' | | callstack.append((name, filename, line, funcname)) | | frame = frame.older() | | addr = int(str(self.return_value), 16) | allocations[addr] = callstack | | | class MemAlloc (gdb.Command): | "Track allocations." | def __init__(self): | super(MemAlloc, self).__init__("memalloc", gdb.COMMAND_NONE) | | def invoke(self, arg, from_tty): | top = gdb.selected_frame() | frame = top.older() | | if frame: | func = frame.function() | | if func: # and func.name.startswith("virAlloc"): | ab = AllocBreak(top, True) | ab.silent = True | | | class MemFree(gdb.Command): | "Track de-allocations." | def __init__(self): | super(MemFree, self).__init__("memfree", gdb.COMMAND_NONE) | | def invoke(self, arg, from_tty): | global allocations | | block = gdb.selected_frame().block() | while block: | for sym in block: | if sym.is_argument: | addr = int(str(gdb.parse_and_eval(sym.name)), 16) | | if addr in allocations: | del allocations[addr] | | return | block = block.superblock | | | class MemReport(gdb.Command): | def __init__(self): | super(MemReport, self).__init__("memreport", gdb.COMMAND_NONE) | | def invoke(self, arg, from_tty): | global allocations | | nr = 1 | for k, v in allocations.iteritems(): | print "{0}. @{1}".format(nr, k) | i = 1 | gap = 0 | nr += 1 | for name, filename, line, funcname in v: | if name: | if gap > 0: | print " #{0} ... [{1}]".format(i, gap) | i += 1 | gap = 0 | print " #{0} {1} {2} {3}:{4}".format(i, name, funcname, filename, line) | i += 1 | else: | gap += 1 | if gap > 0: | print " #{0} ... [{1}]".format(i, gap) | | MemAlloc() | MemFree() | MemReport() `---- ,----[ .gdbinit ] | set pagination off | source memcheck.py | set breakpoint pending on | | break calloc | commands | silent | memalloc | cont | end | | break free | commands | silent | memfree | cont | end | | break malloc | commands | silent | memalloc | cont | end | | disable | | tbreak virInitialize | commands | silent | finish | end `---- Just drop these two files into the current directory, so that GDB will find them. Using this short Java program ,----[ Memcheck.java ] | | package org.libvirt; | | import com.sun.jna.Library; | import com.sun.jna.Native; | | import java.io.InputStream; | import java.io.InputStreamReader; | import java.io.BufferedReader; | import java.io.FileInputStream; | import java.io.IOException; | import java.util.Set; | import java.util.HashSet; | | class Memcheck { | public static void main(String[] args) throws IOException { | Connect conn = null; | Domain dom = null; | | try { | conn = new Connect("test:///default", false); | | dom = conn.domainDefineXML("<domain type='test' id='2'>" + " <name>deftest</name>" | + " <uuid>004b96e1-2d78-c30f-5aa5-f03c87d21e70</uuid>" + " <memory>8388608</memory>" | + " <vcpu>2</vcpu>" + " <os><type arch='i686'>hvm</type></os>" | + " <on_reboot>restart</on_reboot>" + " <on_poweroff>destroy</on_poweroff>" | + " <on_crash>restart</on_crash>" + "</domain>"); | | System.out.println("virDomainGetSchedulerType:" + dom.getSchedulerType()[0]); | | dom.undefine(); | } catch (LibvirtException e) { | System.out.println("exception caught:" + e); | System.out.println(e.getError()); | } finally { | if (conn != null) | try { | dom.free(); | conn.close(); | } catch (LibvirtException e) { | } | } | } | } `---- and running gdb --args java -cp \ /usr/share/java/jna.jar:target/classes/:target/testclasses/ \ org.libvirt.Memcheck with libvirt-java @efbe26d yielded this GDB output: (gdb) run ... 0x00007fffe7dfda14 in ffi_call_unix64 () from /usr/lib/x86_64-linux-gnu/libffi.so.6 Value returned is $1 = 0 (gdb) enable (gdb) c ... (gdb) memreport 1. @140737220921872 #1 testDomainGetSchedulerType testDomainGetSchedulerType /build/buildd/libvirt-0.9.12/./src/test/test_driver.c:2679 #2 virDomainGetSchedulerType virDomainGetSchedulerType /build/buildd/libvirt-0.9.12/./src/libvirt.c:6848 #3 ffi_call_unix64 ? ?:0 #4 ffi_call ? ?:0 #5 ... [1] #6 Java_com_sun_jna_Function_invokePointer ? ?:0 #7 ... [7] Thank you! Evidently, this really fixed the memleak above. Yay! :) -- AV-Test GmbH, Henricistraße 20, 04155 Leipzig, Germany Phone: +49 341 265 310 19 Web:<http://www.av-test.org> Eingetragen am / Registered at: Amtsgericht Stendal (HRB 114076) Geschaeftsfuehrer (CEO): Andreas Marx, Guido Habicht, Maik Morgenstern