RFR(M): 8171181: Supporting heap allocation on alternative memory devices
sangheon.kim
sangheon.kim at oracle.com
Mon Oct 23 21:30:50 UTC 2017
Hi Kishor,
On 10/19/2017 08:00 AM, Kharbas, Kishor wrote:
>
> Hi Sangheon,
>
> Thanks for the review and comments.
>
> I created two webrevs:
>
> webrev.07 : Is the rebase of webrev.06 on jdk10
> (http://cr.openjdk.java.net/~kkharbas/8171181/webrev.07/
> <http://cr.openjdk.java.net/%7Ekkharbas/8171181/webrev.07/>)
>
> webrev.08 : Is incremental webrev over 07.
> (http://cr.openjdk.java.net/~kkharbas/8171181/webrev.08/
> <http://cr.openjdk.java.net/%7Ekkharbas/8171181/webrev.08/>)
>
1. I couldn't apply webrev.07 patch cleanly. Could you test?
Just minor nit: 07 seems not only rebase of webrev.06. i.e. there
seems to have some changes from my comment of alignments.
2. The description in the JEP uses 'AllocateHeapAt' while the patch uses
'HeapDir'.
-----------------------------
src/os/posix/vm/os_posix.cpp
159 (void)strcpy(fullname, dir);
- Please use strncpy instead.
160 (void)strcat(fullname, name_template);
- Please use strncat instead.
180 ::free(fullname);
- os::free().
196 ::free(fullname);
- os::free().
-----------------------------
src/os/windows/vm/os_windows.cpp
2885 char *fullname = (char*)_alloca(strlen(dir) + sizeof(name_template));
- Missing allocation failure handling.
- Please use _malloca instead.
* This function is deprecated because a more secure version is
available; see _malloca.
https://msdn.microsoft.com/en-us/library/wb1s57t5.aspx
2886 (void)strcpy(fullname, dir);
- Please use strncpy instead.
2887 (void)strcat(fullname, name_template);
- Please use strncat instead.
-----------------------------
src/share/vm/runtime/arguments.cpp
3726 }
3727 }
- My previous comment was to add explicit explanation of disabling
UseNUMA and UseNUMAInterleaving.
4636 if(!FLAG_IS_DEFAULT(HeapDir)) {
- Previsouly we checked UseNUMA and UseNUMAInterleaving and then
disabled those. IMHO, I think previous one seems better with more
explanation that we are going to disable those options. i.e. Similar to
os_linux.cpp:4869, a warning message with disabling codes.
4638 }
4639 else if (UseParallelGC || UseParallelOldGC) {
- One line please if this change is still needed.
-> } else if {
-----------------------------
src/share/vm/runtime/os.cpp
1678
- Extra line.
1688 }
1689 else {
-> } else {
My answers are inlined.
> In webrev08 I have addressed all the comments, except for ones below:
>
> ---------------------------------------
>
> src/os/aix/vm/os_aix.cpp
>
> 2514 char* os::pd_attempt_reserve_memory_at(size_t bytes, char*
> requested_addr, bool use_SHM) {
> - Question. Why os_aix has additional parameter at
> pd_attemp_reserve_memory_at()? Probably only AIX has shmated memory
> implementation?
>
> A: Yes that’s correct.
>
Okay.
> --------------------------------------
>
> 137 log_debug(gc, heap, coops)("UseLargePages can't be set with
> HeapDir option.");
> - Is it enough to print log message instead of warning message? i.e.
> Don't we need something at arguments.cpp:3656, similar to NUMA flags?
> A: If don’t disable UseLargePages like UseNUMA because large
> pages can be used for other allocation such as CodeCache.
>
I meant to changing log_debug() to log_warning().
If UseNUMA is enabled, we print warning at arguments.cpp:3725 while
UseLargePages is enabled, we print debug message.
In addition, is this enough? Don't we need to force disabling UseLargePages?
What happens if both options are enabled?
> ------------------------------------
>
> 603 ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t
> alignment, bool large, const char* backing_fs_for_heap)
> - ReservedSpace has '_backing_fd' but the constructor doesn't take it
> as a parameter and only ReservedHeapSpace uses it. This seems not
> ideal, couldn't make it better? I know actual logic is at
> ReservedSpace so it is not convenient to add _backing_fs_for_heap at
> ReservedHeapSapce.
> A: ReservedHeapSpace depends on few functions in ReservedSpace
> such as initialize(), release(). So instead of passing it as argument,
> I set it as a propert of ReservedSpace.
>
Okay.
> -----------------------------------
>
> 1663
> - You removed os::attempt_reserve_memory_at() from os.cpp and split
> into os_posix.cpp and os_windows.cpp.
> But I think you should remain os::attempt_reserve_memory_at() at
> os.cpp and implement os specific stuffs at each os_xxx.cpp files for
> pd_xxx. Of cource move MemTracker function call as well.
> A: I do it this way to reduce the redundant code, If I
> implement in OS specific files in pd_xxx(), the code to replace
> reserved mapping with file mapping
> (replace_existing_mapping_with_dax_file_mapping()) will be redundant.
>
> Still if you feel I will do the change and see how it looks.
>
I would prefer to have pd_xxx() even though there's some redundant code.
Thanks,
Sangheon
> Regards
>
> Kishor
>
> *From:*sangheon.kim [mailto:sangheon.kim at oracle.com]
> *Sent:* Tuesday, September 26, 2017 3:18 PM
> *To:* Kharbas, Kishor <kishor.kharbas at intel.com>;
> 'hotspot-gc-dev at openjdk.java.net' <hotspot-gc-dev at openjdk.java.net>
> *Subject:* Re: RFR(M): 8171181: Supporting heap allocation on
> alternative memory devices
>
> Hi Kishor,
>
> On 07/20/2017 06:34 PM, Kharbas, Kishor wrote:
>
> I have a new version of this patch at
> http://cr.openjdk.java.net/~kkharbas/8171181/webrev.06/
> <http://cr.openjdk.java.net/%7Ekkharbas/8171181/webrev.06/>
>
> This version has been tested on Windows, Linux, Solaris and Mac
> OS. I could not get access to AIX for testing.
>
> I used tmpfs to test the functionality. Cases that were tested were.
>
> 1.Allocation of heap using file mapping when –XX:HeapDir= option
> is used.
>
> 2.Creation of nameless temporary file for Heap allocation which
> prevents access to file using its name.
>
> 3.Correct deletion and freeing up of space allocated for file
> under different exit conditions.
>
> 4.Error handling when path specified is not present, heap size is
> more than size of file system, etc.
>
> Overall seems good.
> I tried to list some missing part.
>
> 1. Please rebase with consolidated repository. (jdk10/hs)
> 2. Build failure on Solaris.
> (Sorry no build error log file, as I tested a few weeks ago, it is
> deleted)
> 3. Have you tested with various heap reserve path using
> HeapBaseMinAddress flag? i.e. to test code path of
> ReservedHeapSpace::try_reserve_heap() and try_reserve_range().
> 4. How about adding HeapDir allocation success message? e.g.
> gc+heap+coops=info
> 5. Adding JTREG test. Probably we would need to verify this allocation
> is succeeded via #4 added allocation success message.
> 6. CSR (Compatibility & Specification Review). At some point, you need
> to file another CR of 'CSR' type to add a new flag of 'HeapDir'.
> 7. It will be much appreciated if you provide incremental webrev. I
> think 06(this version) vs. 07(rebase version) would be hard to get.
> Probably from 08 version.
>
> Here's my comments.
> -----------------------------
> src/os/aix/vm/os_aix.cpp
>
> 2514 char* os::pd_attempt_reserve_memory_at(size_t bytes, char*
> requested_addr, bool use_SHM) {
> - Question. Why os_aix has additional parameter at
> pd_attemp_reserve_memory_at()? Probably only AIX has shmated memory
> implementation?
>
> -----------------------------
> src/os/posix/vm/os_posix.cpp
>
> 148 char *fullname = (char*)::malloc(strlen(dir) +
> sizeof(name_template));
> - Use os::malloc()
>
> 196 int flags;
> 197
> 198 flags = MAP_PRIVATE | MAP_NORESERVE | MAP_ANONYMOUS;
> - Combining 196 and 198 seems better to me.
>
> 200 assert((uintptr_t)requested_addr % os::Linux::page_size() ==
> 0, "unaligned address");
> - Linux dependency on posix file which makes build error on Solaris.
> Probably os::vm_page_size().
>
> 207 addr = (char*)::mmap(requested_addr, bytes, PROT_NONE,
> 208 flags, -1, 0);
> - Missing some spaces? Alignment seems odd to me.
>
> 226 if (ret == -1)
> - Probably you wanted to add handling code? If not, just return ret.
>
> 252 if (addr == MAP_FAILED || (base != NULL && addr != base)) {
> 253 if (addr != MAP_FAILED) {
> 254 if (!os::release_memory(addr, size)) {
> 255 warning("Could not release memory on unsuccessful file
> mapping");
> 256 }
> 257 }
> 258 return NULL;
> 259 }
> - Splitting MAP_FAILED case and another gives better readability to
> me. But this is your call.
>
> 269
> - Extra line.
>
> 284 if (result != NULL && file_desc != -1) {
> 285 if (replace_existing_mapping_with_dax_file_mapping(result,
> bytes, file_desc) == NULL) {
> 286 vm_exit_during_initialization(err_msg("Error in mapping Java
> heap at the given filesystem directory"));
> 287 }
> 288
> MemTracker::record_virtual_memory_reserve_and_commit((address)result,
> bytes, CALLER_PC);
> 289 return result;
> 290 }
> 291 if (result != NULL) {
> 292 MemTracker::record_virtual_memory_reserve((address)result, bytes,
> CALLER_PC);
> 293 }
> - Combining line 284 and 291 seems better to me.
> 284 if (result != NULL) {
> if (file_desc != -1) {
> if (replace_existing_mapping_with_dax_file_mapping(result,
> bytes, file_desc) == NULL) {
> vm_exit_during_initialization(err_msg("Error in mapping
> Java heap at the given filesystem directory"));
> }
> MemTracker::record_virtual_memory_reserve_and_commit((address)result,
> bytes, CALLER_PC);
> } else {
> MemTracker::record_virtual_memory_reserve((address)result, bytes,
> CALLER_PC);
> }
> }
> return result;
>
> -----------------------------
> src/os/windows/vm/os_windows.cpp
> 3141 // if 'base' is not NULL, function will return NULL if it cannot
> get 'base'
> - Start with uppercase.
>
> 3142 //
> - This line seems redundant.
>
> 3151 vm_exit_during_initialization(err_msg("Could not allocate
> sufficient disk space for heap"));
> - heap -> Java heap (same as line 3153)
>
> 3168 assert(base != NULL, "base cannot be NULL");
> - 'base' -> 'Base' or 'Base address'.
>
> 3172
> - Redundant line.
>
> 3230 }
> 3231 else {
> -> } else {
>
> 3278 return reserve_memory(bytes, requested_addr, 0);
> - Is it correct to use '0' not '-1'? It would be better to explain why
> we use hard-coded value here.
>
> -----------------------------
> src/share/vm/memory/universe.cpp
> - No comments
>
> -----------------------------
> src/share/vm/memory/virtualspace.cpp
> - copyright update
>
> 74 const size_t size, bool
> special, bool is_file_mapped= false)
> - Need space between 'is_file_mapped' and '='.
>
> 92 fatal("os::release_memory failed");
> - Typo, 'os::unmap_memory failed'.
>
> 129 // If there is a backing file directory for this VirtualSpace
> then whether
> - This is not VirtualSpace. Probably just 'space'.
>
> 130 // large pages are allocated is upto the filesystem the dir
> resides in.
> - 'dir'? Probably 'backing file for Java heap'.
>
> 137 log_debug(gc, heap, coops)("UseLargePages can't be set with
> HeapDir option.");
> - Is it enough to print log message instead of warning message? i.e.
> Don't we need something at arguments.cpp:3656, similar to NUMA flags?
>
> 191 // unmap_memory will do extra work esp. in Windows
> - esp. -> especially
>
> 282 }
> 283 else {
> -> } else {
>
> 346 // If there is a backing file directory for this VirtualSpace
> then whether
> - Again this is not VirtualSpace, so just 'space'.
>
> 352 if (UseLargePages && (!FLAG_IS_DEFAULT(UseLargePages) ||
> 353 !FLAG_IS_DEFAULT(LargePageSizeInBytes))) {
> - Wrong alignment at line 353. Consider to make same as line 380.
>
> 603 ReservedHeapSpace::ReservedHeapSpace(size_t size, size_t
> alignment, bool large, const char* backing_fs_for_heap)
> - ReservedSpace has '_backing_fd' but the constructor doesn't take it
> as a parameter and only ReservedHeapSpace uses it. This seems not
> ideal, couldn't make it better? I know actual logic is at
> ReservedSpace so it is not convenient to add _backing_fs_for_heap at
> ReservedHeapSapce.
>
> -----------------------------
> src/share/vm/memory/virtualspace.hpp
> 40 int _backing_fd;
> - I would prefer to have better name to describe.
> e.g. as command-line option name is 'HeapDir', _heap_fd or
> _fd_for_heap(similar to below)?
>
> 115 ReservedHeapSpace(size_t size, size_t forced_base_alignment,
> bool large, const char* backingFSforHeap = NULL);
> - Snake case. How about 'fs_for_heap' or 'heap_fs'?
>
> -----------------------------
> src/share/vm/runtime/arguments.cpp
> 3655 FLAG_SET_CMDLINE(bool, UseNUMA, false);
> - (questions) Don't need to add a warning message for
> UseLargePagesSame=true as commented virtualspace.cpp:137?
>
> -----------------------------
> src/share/vm/runtime/globals.hpp
> - No comments
>
> -----------------------------
> src/share/vm/runtime/os.cpp
>
> 1632
> - Extra line.
>
> 1642 }
> 1643 else {
> -> } else {
>
> 1663
> - You removed os::attempt_reserve_memory_at() from os.cpp and split
> into os_posix.cpp and os_windows.cpp.
> But I think you should remain os::attempt_reserve_memory_at() at
> os.cpp and implement os specific stuffs at each os_xxx.cpp files for
> pd_xxx. Of cource move MemTracker function call as well.
>
> -----------------------------
> src/share/vm/runtime/os.hpp
>
> 349 // replace existing reserved memory with file mapping
> - Start with uppercase letter.
>
> Thanks,
> Sangheon
>
>
>
> - Kishor
>
> *From:* Kharbas, Kishor
> *Sent:* Tuesday, July 11, 2017 6:40 PM
> *To:* 'hotspot-gc-dev at openjdk.java.net
> <mailto:hotspot-gc-dev at openjdk.java.net>'
> <hotspot-gc-dev at openjdk.java.net>
> <mailto:hotspot-gc-dev at openjdk.java.net>
> *Cc:* Kharbas, Kishor <kishor.kharbas at intel.com>
> <mailto:kishor.kharbas at intel.com>
> *Subject:* RFR(M): 8171181: Supporting heap allocation on
> alternative memory devices
>
> Greetings,
>
> I have an updated patch for JEP
> https://bugs.openjdk.java.net/browse/JDK-8171181
> <https://bugs.openjdk.java.net/browse/JDK-8171181> at
> http://cr.openjdk.java.net/~kkharbas/8171181/webrev.05
> <http://cr.openjdk.java.net/%7Ekkharbas/8171181/webrev.05>
>
> This patch fixes the bugs pointed earlier and other suggestions to
> make the code less intrusive.
>
> I have also sent this to ‘hotspot-runtime-dev’ mailing list
> (included below).
>
> I would appreciate comments and feedback.
>
> Thanks
>
> Kishor
>
> *From:* Kharbas, Kishor
> *Sent:* Monday, July 10, 2017 1:53 PM
> *To:* hotspot-runtime-dev at openjdk.java.net
> <mailto:hotspot-runtime-dev at openjdk.java.net>
> *Cc:* Kharbas, Kishor <kishor.kharbas at intel.com
> <mailto:kishor.kharbas at intel.com>>
> *Subject:* RFR(M): 8171181: Supporting heap allocation on
> alternative memory devices
>
> Hello all!
>
> I have an updated patch forhttps://bugs.openjdk.java.net/browse/JDK-8171181 athttp://cr.openjdk.java.net/~kkharbas/8171181/webrev.05
> <http://cr.openjdk.java.net/%7Ekkharbas/8171181/webrev.05>
>
> I have lost the old email chain so had to start a fresh one. The
> archived conversation can be found at -
> http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2017-March/022733.html
>
> 1.I have worked on all the comments and fixed the bugs. Mainly
> bugs fixed are related to sigprocmask() and changed the
> implementation such that ‘fd’ is not passed all the way down the
> call stack. Thus minimizing function signature changes.
>
> 2.Patch supports all OS’es. Consolidated all Posix compliant OS’s
> implementation in os_posix.cpp.
>
> 3.The patch is tested on Windows and Linux. Working on testing it
> on other OS’es.
>
> Let me know if this version looks clean and correct.
>
> Thanks
>
> Kishor
>
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