On Mon, May 6, 2024 at 11:43 AM Ian Rogers <irogers@xxxxxxxxxx> wrote: > > On Mon, May 6, 2024 at 11:32 AM Andrii Nakryiko > <andrii.nakryiko@xxxxxxxxx> wrote: > > > > On Sat, May 4, 2024 at 10:09 PM Ian Rogers <irogers@xxxxxxxxxx> wrote: > > > > > > On Sat, May 4, 2024 at 2:57 PM Andrii Nakryiko > > > <andrii.nakryiko@xxxxxxxxx> wrote: > > > > > > > > On Sat, May 4, 2024 at 8:29 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > On Fri, May 03, 2024 at 05:30:06PM -0700, Andrii Nakryiko wrote: > > > > > > Implement a simple tool/benchmark for comparing address "resolution" > > > > > > logic based on textual /proc/<pid>/maps interface and new binary > > > > > > ioctl-based PROCFS_PROCMAP_QUERY command. > > > > > > > > > > Of course an artificial benchmark of "read a whole file" vs. "a tiny > > > > > ioctl" is going to be different, but step back and show how this is > > > > > going to be used in the real world overall. Pounding on this file is > > > > > not a normal operation, right? > > > > > > > > > > > > > It's not artificial at all. It's *exactly* what, say, blazesym library > > > > is doing (see [0], it's Rust and part of the overall library API, I > > > > think C code in this patch is way easier to follow for someone not > > > > familiar with implementation of blazesym, but both implementations are > > > > doing exactly the same sequence of steps). You can do it even less > > > > efficiently by parsing the whole file, building an in-memory lookup > > > > table, then looking up addresses one by one. But that's even slower > > > > and more memory-hungry. So I didn't even bother implementing that, it > > > > would put /proc/<pid>/maps at even more disadvantage. > > > > > > > > Other applications that deal with stack traces (including perf) would > > > > be doing one of those two approaches, depending on circumstances and > > > > level of sophistication of code (and sensitivity to performance). > > > > > > The code in perf doing this is here: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/util/synthetic-events.c#n440 > > > The code is using the api/io.h code: > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/lib/api/io.h > > > Using perf to profile perf it was observed time was spent allocating > > > buffers and locale related activities when using stdio, so io is a > > > lighter weight alternative, albeit with more verbose code than fscanf. > > > You could add this as an alternate /proc/<pid>/maps reader, we have a > > > similar benchmark in `perf bench internals synthesize`. > > > > > > > If I add a new implementation using this ioctl() into > > perf_event__synthesize_mmap_events(), will it be tested from this > > `perf bench internals synthesize`? I'm not too familiar with perf code > > organization, sorry if it's a stupid question. If not, where exactly > > is the code that would be triggered from benchmark? > > Yes it would be triggered :-) Ok, I don't exactly know how to interpret the results (and what the benchmark is doing), but numbers don't seem to be worse. They actually seem to be a bit better. I pushed my code that adds perf integration to [0]. That commit has results, but I'll post them here (with invocation parameters). perf-ioctl is the version with ioctl()-based implementation, perf-parse is, logically, text-parsing version. Here are the results (and see my notes below the results as well): TEXT-BASED ========== # ./perf-parse bench internals synthesize # Running 'internals/synthesize' benchmark: Computing performance of single threaded perf event synthesis by synthesizing events on the perf process itself: Average synthesis took: 80.311 usec (+- 0.077 usec) Average num. events: 32.000 (+- 0.000) Average time per event 2.510 usec Average data synthesis took: 84.429 usec (+- 0.066 usec) Average num. events: 179.000 (+- 0.000) Average time per event 0.472 usec # ./perf-parse bench internals synthesize # Running 'internals/synthesize' benchmark: Computing performance of single threaded perf event synthesis by synthesizing events on the perf process itself: Average synthesis took: 79.900 usec (+- 0.077 usec) Average num. events: 32.000 (+- 0.000) Average time per event 2.497 usec Average data synthesis took: 84.832 usec (+- 0.074 usec) Average num. events: 180.000 (+- 0.000) Average time per event 0.471 usec # ./perf-parse bench internals synthesize --mt -M 8 # Running 'internals/synthesize' benchmark: Computing performance of multi threaded perf event synthesis by synthesizing events on CPU 0: Number of synthesis threads: 1 Average synthesis took: 36338.100 usec (+- 406.091 usec) Average num. events: 14091.300 (+- 7.433) Average time per event 2.579 usec Number of synthesis threads: 2 Average synthesis took: 37071.200 usec (+- 746.498 usec) Average num. events: 14085.900 (+- 1.900) Average time per event 2.632 usec Number of synthesis threads: 3 Average synthesis took: 33932.300 usec (+- 626.861 usec) Average num. events: 14085.900 (+- 1.900) Average time per event 2.409 usec Number of synthesis threads: 4 Average synthesis took: 33822.700 usec (+- 506.290 usec) Average num. events: 14099.200 (+- 8.761) Average time per event 2.399 usec Number of synthesis threads: 5 Average synthesis took: 33348.200 usec (+- 389.771 usec) Average num. events: 14085.900 (+- 1.900) Average time per event 2.367 usec Number of synthesis threads: 6 Average synthesis took: 33269.600 usec (+- 350.341 usec) Average num. events: 14084.000 (+- 0.000) Average time per event 2.362 usec Number of synthesis threads: 7 Average synthesis took: 32663.900 usec (+- 338.870 usec) Average num. events: 14085.900 (+- 1.900) Average time per event 2.319 usec Number of synthesis threads: 8 Average synthesis took: 32748.400 usec (+- 285.450 usec) Average num. events: 14085.900 (+- 1.900) Average time per event 2.325 usec IOCTL-BASED =========== # ./perf-ioctl bench internals synthesize # Running 'internals/synthesize' benchmark: Computing performance of single threaded perf event synthesis by synthesizing events on the perf process itself: Average synthesis took: 72.996 usec (+- 0.076 usec) Average num. events: 31.000 (+- 0.000) Average time per event 2.355 usec Average data synthesis took: 79.067 usec (+- 0.074 usec) Average num. events: 178.000 (+- 0.000) Average time per event 0.444 usec # ./perf-ioctl bench internals synthesize # Running 'internals/synthesize' benchmark: Computing performance of single threaded perf event synthesis by synthesizing events on the perf process itself: Average synthesis took: 73.921 usec (+- 0.073 usec) Average num. events: 31.000 (+- 0.000) Average time per event 2.385 usec Average data synthesis took: 80.545 usec (+- 0.070 usec) Average num. events: 178.000 (+- 0.000) Average time per event 0.453 usec # ./perf-ioctl bench internals synthesize --mt -M 8 # Running 'internals/synthesize' benchmark: Computing performance of multi threaded perf event synthesis by synthesizing events on CPU 0: Number of synthesis threads: 1 Average synthesis took: 35609.500 usec (+- 428.576 usec) Average num. events: 14040.700 (+- 1.700) Average time per event 2.536 usec Number of synthesis threads: 2 Average synthesis took: 34293.800 usec (+- 453.811 usec) Average num. events: 14040.700 (+- 1.700) Average time per event 2.442 usec Number of synthesis threads: 3 Average synthesis took: 32385.200 usec (+- 363.106 usec) Average num. events: 14040.700 (+- 1.700) Average time per event 2.307 usec Number of synthesis threads: 4 Average synthesis took: 33113.100 usec (+- 553.931 usec) Average num. events: 14054.500 (+- 11.469) Average time per event 2.356 usec Number of synthesis threads: 5 Average synthesis took: 31600.600 usec (+- 297.349 usec) Average num. events: 14012.500 (+- 4.590) Average time per event 2.255 usec Number of synthesis threads: 6 Average synthesis took: 32309.900 usec (+- 472.225 usec) Average num. events: 14004.000 (+- 0.000) Average time per event 2.307 usec Number of synthesis threads: 7 Average synthesis took: 31400.100 usec (+- 206.261 usec) Average num. events: 14004.800 (+- 0.800) Average time per event 2.242 usec Number of synthesis threads: 8 Average synthesis took: 31601.400 usec (+- 303.350 usec) Average num. events: 14005.700 (+- 1.700) Average time per event 2.256 usec I also double-checked (using strace) that it does what it is supposed to do, and it seems like everything checks out. Here's text-based strace log: openat(AT_FDCWD, "/proc/35876/task/35876/maps", O_RDONLY) = 3 read(3, "00400000-0040c000 r--p 00000000 "..., 8192) = 3997 read(3, "7f519d4d3000-7f519d516000 r--p 0"..., 8192) = 4025 read(3, "7f519dc3d000-7f519dc44000 r-xp 0"..., 8192) = 4048 read(3, "7f519dd2d000-7f519dd2f000 r--p 0"..., 8192) = 4017 read(3, "7f519dff6000-7f519dff8000 r--p 0"..., 8192) = 2744 read(3, "", 8192) = 0 close(3) = 0 BTW, note how the kernel doesn't serve more than 4KB of data, even though perf provides 8KB buffer (that's to Greg's question about optimizing using bigger buffers, I suspect without seq_file changes, it won't work). And here's an abbreviated log for ioctl version, it has lots more (but much faster) ioctl() syscalls, given it dumps everything: openat(AT_FDCWD, "/proc/36380/task/36380/maps", O_RDONLY) = 3 ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x9f, 0x1, 0x60), 0x7fff6b603d50) = 0 ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x9f, 0x1, 0x60), 0x7fff6b603d50) = 0 ... 195 ioctl() calls in total ... ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x9f, 0x1, 0x60), 0x7fff6b603d50) = 0 ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x9f, 0x1, 0x60), 0x7fff6b603d50) = 0 ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x9f, 0x1, 0x60), 0x7fff6b603d50) = 0 ioctl(3, _IOC(_IOC_READ|_IOC_WRITE, 0x9f, 0x1, 0x60), 0x7fff6b603d50) = -1 ENOENT (No such file or directory) close(3) = 0 So, it's not the optimal usage of this API, and yet it's still better (or at least not worse) than text-based API. [0] https://github.com/anakryiko/linux/commit/0841fe675ed30f5605c5b228e18f5612ea253b35 > > Thanks, > Ian > > > > Thanks, > > > Ian > > > > > > > [0] https://github.com/libbpf/blazesym/blob/ee9b48a80c0b4499118a1e8e5d901cddb2b33ab1/src/normalize/user.rs#L193 > > > > > > > > > thanks, > > > > > > > > > > greg k-h > > > >
