perf-kvm(1) =========== NAME ---- perf-kvm - Tool to trace/measure kvm guest os SYNOPSIS -------- [verse] 'perf kvm' [--host] [--guest] [--guestmount= [--guestkallsyms= --guestmodules= | --guestvmlinux=]] {top|record|report|diff|buildid-list} [] 'perf kvm' [--host] [--guest] [--guestkallsyms= --guestmodules= | --guestvmlinux=] {top|record|report|diff|buildid-list|stat} [] 'perf kvm stat [record|report|live] [] DESCRIPTION ----------- There are a couple of variants of perf kvm: 'perf kvm [options] top ' to generates and displays a performance counter profile of guest os in realtime of an arbitrary workload. 'perf kvm record ' to record the performance counter profile of an arbitrary workload and save it into a perf data file. We set the default behavior of perf kvm as --guest, so if neither --host nor --guest is input, the perf data file name is perf.data.guest. If --host is input, the perf data file name is perf.data.kvm. If you want to record data into perf.data.host, please input --host --no-guest. The behaviors are shown as following: Default('') -> perf.data.guest --host -> perf.data.kvm --guest -> perf.data.guest --host --guest -> perf.data.kvm --host --no-guest -> perf.data.host 'perf kvm report' to display the performance counter profile information recorded via perf kvm record. 'perf kvm diff' to displays the performance difference amongst two perf.data files captured via perf record. 'perf kvm buildid-list' to display the buildids found in a perf data file, so that other tools can be used to fetch packages with matching symbol tables for use by perf report. As buildid is read from /sys/kernel/notes in os, then if you want to list the buildid for guest, please make sure your perf data file was captured with --guestmount in perf kvm record. 'perf kvm stat ' to run a command and gather performance counter statistics. Especially, perf 'kvm stat record/report' generates a statistical analysis of KVM events. Currently, vmexit, mmio (x86 only) and ioport (x86 only) events are supported. 'perf kvm stat record ' records kvm events and the events between start and end . And this command produces a file which contains tracing results of kvm events. 'perf kvm stat report' reports statistical data which includes events handled time, samples, and so on. 'perf kvm stat live' reports statistical data in a live mode (similar to record + report but with statistical data updated live at a given display rate). OPTIONS ------- -i:: --input=:: Input file name. -o:: --output=:: Output file name. --host:: Collect host side performance profile. --guest:: Collect guest side performance profile. --guestmount=:: Guest os root file system mount directory. Users mounts guest os root directories under by a specific filesystem access method, typically, sshfs. For example, start 2 guest os. The one's pid is 8888 and the other's is 9999. #mkdir ~/guestmount; cd ~/guestmount #sshfs -o allow_other,direct_io -p 5551 localhost:/ 8888/ #sshfs -o allow_other,direct_io -p 5552 localhost:/ 9999/ #perf kvm --host --guest --guestmount=~/guestmount top --guestkallsyms=:: Guest os /proc/kallsyms file copy. 'perf' kvm' reads it to get guest kernel symbols. Users copy it out from guest os. --guestmodules=:: Guest os /proc/modules file copy. 'perf' kvm' reads it to get guest kernel module information. Users copy it out from guest os. --guestvmlinux=:: Guest os kernel vmlinux. -v:: --verbose:: Be more verbose (show counter open errors, etc). STAT REPORT OPTIONS ------------------- --vcpu=:: analyze events which occur on this vcpu. (default: all vcpus) --event=:: event to be analyzed. Possible values: vmexit, mmio (x86 only), ioport (x86 only). (default: vmexit) -k:: --key=:: Sorting key. Possible values: sample (default, sort by samples number), time (sort by average time). -p:: --pid=:: Analyze events only for given process ID(s) (comma separated list). STAT LIVE OPTIONS ----------------- -d:: --display:: Time in seconds between display updates -m:: --mmap-pages=:: Number of mmap data pages (must be a power of two) or size specification with appended unit character - B/K/M/G. The size is rounded up to have nearest pages power of two value. -a:: --all-cpus:: System-wide collection from all CPUs. -p:: --pid=:: Analyze events only for given process ID(s) (comma separated list). --vcpu=:: analyze events which occur on this vcpu. (default: all vcpus) --event=:: event to be analyzed. Possible values: vmexit, mmio (x86 only), ioport (x86 only). (default: vmexit) -k:: --key=:: Sorting key. Possible values: sample (default, sort by samples number), time (sort by average time). --duration=:: Show events other than HLT (x86 only) or Wait state (s390 only) that take longer than duration usecs. --proc-map-timeout:: When processing pre-existing threads /proc/XXX/mmap, it may take a long time, because the file may be huge. A time out is needed in such cases. This option sets the time out limit. The default value is 500 ms. SEE ALSO -------- linkperf:perf-top[1], linkperf:perf-record[1], linkperf:perf-report[1], linkperf:perf-diff[1], linkperf:perf-buildid-list[1], linkperf:perf-stat[1] olspan='2' class='oid'>2c5d9555d6d937966d79d4c6529a5f7b9206e405 (diff)
drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()
I've seen this trigger twice now, where the i915_gem_object_to_ggtt() call in intel_unpin_fb_obj() returns NULL, resulting in an oops immediately afterwards as the (inlined) call to i915_vma_unpin_fence() tries to dereference it. It seems to be some race condition where the object is going away at shutdown time, since both times happened when shutting down the X server. The call chains were different: - VT ioctl(KDSETMODE, KD_TEXT): intel_cleanup_plane_fb+0x5b/0xa0 [i915] drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper] intel_atomic_commit_tail+0x749/0xfe0 [i915] intel_atomic_commit+0x3cb/0x4f0 [i915] drm_atomic_commit+0x4b/0x50 [drm] restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper] drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper] drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper] intel_fbdev_set_par+0x18/0x70 [i915] fb_set_var+0x236/0x460 fbcon_blank+0x30f/0x350 do_unblank_screen+0xd2/0x1a0 vt_ioctl+0x507/0x12a0 tty_ioctl+0x355/0xc30 do_vfs_ioctl+0xa3/0x5e0 SyS_ioctl+0x79/0x90 entry_SYSCALL_64_fastpath+0x13/0x94 - i915 unpin_work workqueue: intel_unpin_work_fn+0x58/0x140 [i915] process_one_work+0x1f1/0x480 worker_thread+0x48/0x4d0 kthread+0x101/0x140 and this patch purely papers over the issue by adding a NULL pointer check and a WARN_ON_ONCE() to avoid the oops that would then generally make the machine unresponsive. Other callers of i915_gem_object_to_ggtt() seem to also check for the returned pointer being NULL and warn about it, so this clearly has happened before in other places. [ Reported it originally to the i915 developers on Jan 8, applying the ugly workaround on my own now after triggering the problem for the second time with no feedback. This is likely to be the same bug reported as https://bugs.freedesktop.org/show_bug.cgi?id=98829 https://bugs.freedesktop.org/show_bug.cgi?id=99134 which has a patch for the underlying problem, but it hasn't gotten to me, so I'm applying the workaround. ] Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com> Cc: Imre Deak <imre.deak@intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/xfs/libxfs/xfs_log_rlimit.c')