On Sun, Jun 28, 2020 at 04:34:51PM +0300, Amir Goldstein wrote: > > > > > #0 0x55f6da0120d9 base::debug::CollectStackTrace() > > > > > #1 0x55f6d9f75246 base::debug::StackTrace::StackTrace() > > > > > #2 0x55f6da01170a base::debug::(anonymous namespace)::StackDumpSignalHandler() > > > > > #3 0x55f6da011cfe base::debug::(anonymous namespace)::StackDumpSignalHandler() > > > > > #4 0x7ff46643ab20 (/usr/lib64/libpthread-2.30.so+0x14b1f) > > > > > #5 0x7ff462d87625 __GI_raise > > > > > #6 0x7ff462d708d9 __GI_abort > > > > > #7 0x55f6da0112d5 base::debug::BreakDebugger() > > > > > #8 0x55f6d9f86405 logging::LogMessage::~LogMessage() > > > > > #9 0x55f6d7ed5488 content::(anonymous namespace)::IntentionallyCrashBrowserForUnusableGpuProcess() > > > > > #10 0x55f6d7ed8479 content::GpuDataManagerImplPrivate::FallBackToNextGpuMode() > > > > > #11 0x55f6d7ed4eef content::GpuDataManagerImpl::FallBackToNextGpuMode() > > > > > #12 0x55f6d7ee0f41 content::GpuProcessHost::RecordProcessCrash() > > > > > #13 0x55f6d7ee105d content::GpuProcessHost::OnProcessCrashed() > > > > > #14 0x55f6d7cbe308 content::BrowserChildProcessHostImpl::OnChildDisconnected() > > > > > #15 0x55f6da8b511a IPC::ChannelMojo::OnPipeError() > > > > > #16 0x55f6da13cd62 mojo::InterfaceEndpointClient::NotifyError() > > > > > #17 0x55f6da8c1f9d IPC::(anonymous namespace)::ChannelAssociatedGroupController::OnPipeError() > > > > > #18 0x55f6da138968 mojo::Connector::HandleError() > > > > > #19 0x55f6da15bce7 mojo::SimpleWatcher::OnHandleReady() > > > > > #20 0x55f6da15c0fb mojo::SimpleWatcher::Context::CallNotify() > > > > > #21 0x55f6d78eaa73 mojo::core::WatcherDispatcher::InvokeWatchCallback() > > > > > #22 0x55f6d78ea38f mojo::core::Watch::InvokeCallback() > > > > > #23 0x55f6d78e6efa mojo::core::RequestContext::~RequestContext() > > > > > #24 0x55f6d78db76a mojo::core::NodeChannel::OnChannelError() > > > > > #25 0x55f6d78f232a mojo::core::(anonymous namespace)::ChannelPosix::OnFileCanReadWithoutBlocking() > > > > > #26 0x55f6da03345e base::MessagePumpLibevent::OnLibeventNotification() > > > > > #27 0x55f6da0f9b2d event_base_loop > > > > > #28 0x55f6da03316d base::MessagePumpLibevent::Run() > > > > > #29 0x55f6d9fd79c9 base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::Run() > > > > > #30 0x55f6d9fada7a base::RunLoop::Run() > > > > > #31 0x55f6d7ce6324 content::BrowserProcessSubThread::IOThreadRun() > > > > > #32 0x55f6d9fe0cb8 base::Thread::ThreadMain() > > > > > #33 0x55f6da024705 base::(anonymous namespace)::ThreadFunc() > > > > > #34 0x7ff46642f4e2 start_thread > > > > > #35 0x7ff462e4c6a3 __GI___clone > > > > > r8: 0000000000000000 r9: 00007ff44e6a58d0 r10: 0000000000000008 r11: 0000000000000246 > > > > > r12: 00007ff44e6a6b40 r13: 00007ff44e6a6d00 r14: 000000000000006d r15: 00007ff44e6a6b30 > > > > > di: 0000000000000002 si: 00007ff44e6a58d0 bp: 00007ff44e6a5b20 bx: 00007ff44e6a9700 > > > > > dx: 0000000000000000 ax: 0000000000000000 cx: 00007ff462d87625 sp: 00007ff44e6a58d0 > > > > > ip: 00007ff462d87625 efl: 0000000000000246 cgf: 002b000000000033 erf: 0000000000000000 > > > > > trp: 0000000000000000 msk: 0000000000000000 cr2: 0000000000000000 > > > > > [end of stack trace] > > > > > Calling _exit(1). Core file will not be generated. > > > > > > > > > > > > > > > > > > I guess this answers our question whether we could disable fsnoitfy > > > > watches on pseudo inodes.... > > > > > > > > From comments like these in chromium code: > > > > https://chromium.googlesource.com/chromium/src/+/master/mojo/core/watcher_dispatcher.cc#77 > > > > https://chromium.googlesource.com/chromium/src/+/master/base/files/file_descriptor_watcher_posix.cc#176 > > > > https://chromium.googlesource.com/chromium/src/+/master/ipc/ipc_channel_mojo.cc#240 > > > > > > > > I am taking a wild guess that the missing FS_CLOSE event on anonymous pipes is > > > > the cause for regression. > > > > > > > > The motivation for the patch "fs: Do not check if there is a fsnotify > > > > watcher on pseudo inodes" > > > > was performance, but actually, FS_CLOSE and FS_OPEN events probably do > > > > not impact > > > > performance as FS_MODIFY and FS_ACCESS. > > > > > > > > Mel, > > > > > > > > Do your perf results support the claim above? > > > > > > > > Jan/Linus, > > > > > > > > Do you agree that dropping FS_MODIFY/FS_ACCESS events for FMODE_STREAM > > > > files as a general rule should be safe? > > > > > > > > Maxim, can you try if the attached patch fixes the chromium regression. > > > > It is expected to leave the FS_OPEN/FS_CLOSE events on anonymous pipes > > > > but drop the FS_MODIFY/FS_ACCESS events. > > > Tested this (in the VM this time) and it works. > > > > > > Note that this should be changed to 'return' since function returns void. > > > > + if (file->f_mode & FMODE_STREAM) > > + return 0; > > > > Right sorry. Didn't pay attention to the build warnings. > > Now only left to see if this approach is acceptable and if it also > fixes the performance issue reported by Mel. > Thanks Amir! The performance seems fine and I think the patch is ok. If there is an issue with special casing FMODE_STREAM then the alternative would be to special case pipes with FMODE_NONOTIFY specifically as pipes appear to be the pseudo inode that is most affected by fsnotify checks. -- Mel Gorman SUSE Labs
