| Message ID | a108c800-d6c1-fac1-b73b-e390e579e6ef@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | admin-guide: extend perf-security with resource control, data categories and privileged users | expand |
On Thu, 7 Feb 2019, Alexey Budankov wrote: General note: Please stay in the 80 char limit for all of the text. > +The perf_events system call API [2]_ allocates file descriptors for every configured > +PMU event. Open file descriptors are a per-process accountable resource governed > +by the RLIMIT_NOFILE [11]_ limit (ulimit -n), which is usually derived from the login > +shell process. When configuring Perf collection for a long list of events on a > +large server system, this limit can be easily hit preventing required monitoring > +configuration. I'd move this sentence into a different paragraph and keep those related to RLIMIT_NOFILE together. > ... RLIMIT_NOFILE limit can be increased on per-user basis modifying > +content of the limits.conf file [12]_ on some systems. On some systems? > Ordinarily, a Perf sampling session > +(perf record) requires an amount of open perf_event file descriptors that is not > +less than a number of monitored events multiplied by a number of monitored CPUs. s/a number of/the number of/ The ordinary use case is: perf CMD pile-of-events PROCESS which does not specify the monitored CPUs at all. Then the number of file descriptors is NR_EVENTS * NR_ONLINE_CPUS. > +An amount of memory available to user processes for capturing performance monitoring The amount ... > +data is governed by the perf_event_mlock_kb [2]_ setting. This perf_event specific > +resource setting defines overall per-cpu limits of memory allowed for mapping > +by the user processes to execute performance monitoring. The setting essentially > +extends the RLIMIT_MEMLOCK [11]_ limit, but only for memory regions mapped specially s/specially/specifically/ > +for capturing monitored performance events and related data. > + > +For example, if a machine has eight cores and perf_event_mlock_kb limit is set > +to 516 KiB, then a user process is provided with 516 KiB * 8 = 4128 KiB of memory > +above the RLIMIT_MEMLOCK limit (ulimit -l) for perf_event mmap buffers. In particular, > +this means that, if the user wants to start two or more performance monitoring > +processes, the user is required to manually distribute available 4128 KiB between the distribute the available > +monitoring processes, for example, using the --mmap-pages Perf record mode option. > +Otherwise, the first started performance monitoring process allocates all available > +4128 KiB and the other processes will fail to proceed due to the lack of memory. > + > +RLIMIT_MEMLOCK and perf_event_mlock_kb resource costraints are ignored for constraints. > +processes with the CAP_IPC_LOCK capability. Thus, perf_events/Perf privileged users what means perf_events/Perf ? > +can be provided with memory above the constraints for perf_events/Perf performance > +monitoring purpose by providing the Perf executable with CAP_IPC_LOCK capability. Thanks, tglx
On 11.02.2019 1:34, Thomas Gleixner wrote: > On Thu, 7 Feb 2019, Alexey Budankov wrote: > > General note: Please stay in the 80 char limit for all of the text. Yes, sure. [PATCH v2 4/4] implements wrapping at 72 columns. > >> +The perf_events system call API [2]_ allocates file descriptors for every configured >> +PMU event. Open file descriptors are a per-process accountable resource governed >> +by the RLIMIT_NOFILE [11]_ limit (ulimit -n), which is usually derived from the login >> +shell process. When configuring Perf collection for a long list of events on a >> +large server system, this limit can be easily hit preventing required monitoring >> +configuration. > > I'd move this sentence into a different paragraph and keep those related to > RLIMIT_NOFILE together. Makes sense. Let's have these two paragraphs: Open file descriptors +++++++++++++++++++++ Memory allocation +++++++++++++++++ > >> ... RLIMIT_NOFILE limit can be increased on per-user basis modifying >> +content of the limits.conf file [12]_ on some systems. > > On some systems? Well, let's avoid this subtlety and have it like: 'RLIMIT_NOFILE limit can be increased on per-user basis modifying content of the limits.conf file [12]_ .' > >> Ordinarily, a Perf sampling session >> +(perf record) requires an amount of open perf_event file descriptors that is not >> +less than a number of monitored events multiplied by a number of monitored CPUs. > > s/a number of/the number of/ Accepted. > > The ordinary use case is: > > perf CMD pile-of-events PROCESS > > which does not specify the monitored CPUs at all. Then the number of file > descriptors is NR_EVENTS * NR_ONLINE_CPUS. > >> +An amount of memory available to user processes for capturing performance monitoring > > The amount ... Accepted. > >> +data is governed by the perf_event_mlock_kb [2]_ setting. This perf_event specific >> +resource setting defines overall per-cpu limits of memory allowed for mapping >> +by the user processes to execute performance monitoring. The setting essentially >> +extends the RLIMIT_MEMLOCK [11]_ limit, but only for memory regions mapped specially > > s/specially/specifically/ Accepted. > >> +for capturing monitored performance events and related data. >> + >> +For example, if a machine has eight cores and perf_event_mlock_kb limit is set >> +to 516 KiB, then a user process is provided with 516 KiB * 8 = 4128 KiB of memory >> +above the RLIMIT_MEMLOCK limit (ulimit -l) for perf_event mmap buffers. In particular, >> +this means that, if the user wants to start two or more performance monitoring >> +processes, the user is required to manually distribute available 4128 KiB between the > > distribute the available Accepted. > >> +monitoring processes, for example, using the --mmap-pages Perf record mode option. >> +Otherwise, the first started performance monitoring process allocates all available >> +4128 KiB and the other processes will fail to proceed due to the lack of memory. >> + >> +RLIMIT_MEMLOCK and perf_event_mlock_kb resource costraints are ignored for > > constraints. Accepted. > >> +processes with the CAP_IPC_LOCK capability. Thus, perf_events/Perf privileged users > > what means perf_events/Perf ? 'perf_events/Perf privileged users' refers to the paragraph about privileged users. 'perf_events/Perf' means exact combination of the kernel subsystem (perf_events) and the privileged Perf tool (Perf) executable that enables certain group of users with performance monitoring capabilities without scope limit. > >> +can be provided with memory above the constraints for perf_events/Perf performance >> +monitoring purpose by providing the Perf executable with CAP_IPC_LOCK capability. > > Thanks, > > tglx > Thanks, Alexey
On Mon, 11 Feb 2019, Alexey Budankov wrote: > On 11.02.2019 1:34, Thomas Gleixner wrote: > > On Thu, 7 Feb 2019, Alexey Budankov wrote: > > > > General note: Please stay in the 80 char limit for all of the text. > > Yes, sure. [PATCH v2 4/4] implements wrapping at 72 columns. So you provide crappy formatted stuff first, just to reformat it at the end. I'm missing the logic behind that. Thanks, tglx
On 11.02.2019 17:15, Thomas Gleixner wrote: > On Mon, 11 Feb 2019, Alexey Budankov wrote: >> On 11.02.2019 1:34, Thomas Gleixner wrote: >>> On Thu, 7 Feb 2019, Alexey Budankov wrote: >>> >>> General note: Please stay in the 80 char limit for all of the text. >> >> Yes, sure. [PATCH v2 4/4] implements wrapping at 72 columns. > > So you provide crappy formatted stuff first, just to reformat it at the > end. I'm missing the logic behind that. The logic is not to mix new content review with the whole doc formatting in the end. Thanks, Alexey > > Thanks, > > tglx >
diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst index f73ebfe9bfe2..3915f07b9dea 100644 --- a/Documentation/admin-guide/perf-security.rst +++ b/Documentation/admin-guide/perf-security.rst @@ -84,6 +84,40 @@ governed by perf_event_paranoid [2]_ setting: locking limit is imposed but ignored for unprivileged processes with CAP_IPC_LOCK capability. +perf_events/Perf resource control +--------------------------------- + +The perf_events system call API [2]_ allocates file descriptors for every configured +PMU event. Open file descriptors are a per-process accountable resource governed +by the RLIMIT_NOFILE [11]_ limit (ulimit -n), which is usually derived from the login +shell process. When configuring Perf collection for a long list of events on a +large server system, this limit can be easily hit preventing required monitoring +configuration. RLIMIT_NOFILE limit can be increased on per-user basis modifying +content of the limits.conf file [12]_ on some systems. Ordinarily, a Perf sampling session +(perf record) requires an amount of open perf_event file descriptors that is not +less than a number of monitored events multiplied by a number of monitored CPUs. + +An amount of memory available to user processes for capturing performance monitoring +data is governed by the perf_event_mlock_kb [2]_ setting. This perf_event specific +resource setting defines overall per-cpu limits of memory allowed for mapping +by the user processes to execute performance monitoring. The setting essentially +extends the RLIMIT_MEMLOCK [11]_ limit, but only for memory regions mapped specially +for capturing monitored performance events and related data. + +For example, if a machine has eight cores and perf_event_mlock_kb limit is set +to 516 KiB, then a user process is provided with 516 KiB * 8 = 4128 KiB of memory +above the RLIMIT_MEMLOCK limit (ulimit -l) for perf_event mmap buffers. In particular, +this means that, if the user wants to start two or more performance monitoring +processes, the user is required to manually distribute available 4128 KiB between the +monitoring processes, for example, using the --mmap-pages Perf record mode option. +Otherwise, the first started performance monitoring process allocates all available +4128 KiB and the other processes will fail to proceed due to the lack of memory. + +RLIMIT_MEMLOCK and perf_event_mlock_kb resource costraints are ignored for +processes with the CAP_IPC_LOCK capability. Thus, perf_events/Perf privileged users +can be provided with memory above the constraints for perf_events/Perf performance +monitoring purpose by providing the Perf executable with CAP_IPC_LOCK capability. + Bibliography ------------ @@ -94,4 +128,6 @@ Bibliography .. [5] `<https://www.kernel.org/doc/html/latest/security/credentials.html>`_ .. [6] `<http://man7.org/linux/man-pages/man7/capabilities.7.html>`_ .. [7] `<http://man7.org/linux/man-pages/man2/ptrace.2.html>`_ +.. [11] `<http://man7.org/linux/man-pages/man2/getrlimit.2.html>`_ +.. [12] `<http://man7.org/linux/man-pages/man5/limits.conf.5.html>`_
Extend perf-security.rst file with perf_events/Perf resource control section describing RLIMIT_NOFILE and perf_event_mlock_kb settings for performance monitoring user processes. Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com> --- Changes in v2: - applied comments on v1 --- Documentation/admin-guide/perf-security.rst | 36 +++++++++++++++++++++ 1 file changed, 36 insertions(+)