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a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=Wb1JkmetP80A:10 a=GoEa3M9JfhUA:10 a=yPCof4ZbAAAA:8 a=bM5EEiRleyLCrYxGCLkA:9 a=CjuIK1q_8ugA:10 cc=ntf awl=host:12061 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNzE2MDE3MiBTYWx0ZWRfX8o9cHLkYZW/B iExjAiU9yaGPdUQ3LndgYrKAro0hy6VsZDhVD3Ctn7UeFCle4Vt8R4+6V03L+bKTBTKrqyeT4IQ 3J2Q83EB29yLl9DcLUSxJpscEIMhrRLviW8lolnMq2hbV4wE9bZoWtEnUxj6RU3XbFnidyffLMz J0ZZ6BvQqcjZn9MECEGSjSBn2ypEOEtNvweeuHVSqesZyuNesPJjnIUbp/sJj4cPttSdfWIq4nP 2jZ7BzBUljBoFK3qsLQkwhQ8l54sDJAC6te5UBJVNc4xQASZ8HFgijsJRm10ocDHETnZ24i53Gq 6sU2/GnBX2jyi+X7ShgHh+1F9tea88iCklbAiq77DAb7eF45t25sLQccAlBLYdEqviVbNcAq1R6 BgAWIPhvBNslUTM8Yn0SrephHyKh28BJgbbWWFCxHL0nm2+IpiTGIKGDbilLr/9EyYfCS1AE X-Proofpoint-GUID: JioJsytDQDlvPsZws0mkiP9GBlaSqsOF On Thu, May 01, 2025 at 02:22:50PM -0400, eugene.loh--- via DTrace-devel wrote: > From: Eugene Loh > > The dt_bpf_map_lookup_fd(dtp->dt_aggmap_fd, &cpu) call that is used to > snap or truncate aggregations takes a few milliseconds, which seems all > right. For large systems (e.g., 100 CPUs) and many truncations (e.g., > tst.trunc.d, etc.), however, a trunc() might end up costing a minute on > the consumer side, which is unreasonable and causes such tests to time > out. The run time is due almost exclusively to looking up the per-CPU > agg map ID. Of course, we only go from 2 bpf() syscalls per call to 1 bpf() syscall per call. Have you collected timings for the two kinds of bpf calls we use? I would actually expect that the larger cost lies with the bpf_map_get_fd_by_id() one rather than the bpf_map_lookup() since the fd_by_id needs to allocate an fd and link it with a map. In all, how bad would it be if we were to just keep the fds open for the per-CPU aggregation data, and not having to do these bpf syscalls at all. But we could end up with 100s of fds open of course... > Cache the per-CPU agg map IDs. > > Signed-off-by: Eugene Loh > --- > libdtrace/dt_aggregate.c | 5 ++--- > libdtrace/dt_bpf.c | 6 ++++++ > libdtrace/dt_impl.h | 1 + > libdtrace/dt_open.c | 1 + > 4 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/libdtrace/dt_aggregate.c b/libdtrace/dt_aggregate.c > index 9e47fcab7..86f9d4d5b 100644 > --- a/libdtrace/dt_aggregate.c > +++ b/libdtrace/dt_aggregate.c > @@ -800,7 +800,7 @@ dtrace_aggregate_snap(dtrace_hdl_t *dtp) > > for (i = 0; i < dtp->dt_conf.num_online_cpus; i++) { > int cpu = dtp->dt_conf.cpus[i].cpu_id; > - int fd = dt_bpf_map_lookup_fd(dtp->dt_aggmap_fd, &cpu); > + int fd = dt_bpf_map_get_fd_by_id(dtp->dt_aggmap_ids[i]); > > if (fd < 0) > return DTRACE_WORKSTATUS_ERROR; > @@ -1232,8 +1232,7 @@ dt_aggwalk_remove(dtrace_hdl_t *dtp, dt_ahashent_t *h) > memcpy(key, agd->dtada_key, agd->dtada_desc->dtagd_ksize); > > for (i = 0; i < ncpus; i++) { > - int cpu = dtp->dt_conf.cpus[i].cpu_id; > - int fd = dt_bpf_map_lookup_fd(dtp->dt_aggmap_fd, &cpu); > + int fd = dt_bpf_map_get_fd_by_id(dtp->dt_aggmap_ids[i]); > > if (fd < 0) > return DTRACE_WORKSTATUS_ERROR; > diff --git a/libdtrace/dt_bpf.c b/libdtrace/dt_bpf.c > index d6722cbd1..635780738 100644 > --- a/libdtrace/dt_bpf.c > +++ b/libdtrace/dt_bpf.c > @@ -689,6 +689,10 @@ gmap_create_aggs(dtrace_hdl_t *dtp) > if (dtp->dt_aggmap_fd == -1) > return -1; > > + dtp->dt_aggmap_ids = dt_calloc(dtp, dtp->dt_conf.num_online_cpus, sizeof(int)); > + if (dtp->dt_aggmap_ids == NULL) > + return dt_set_errno(dtp, EDT_NOMEM); > + > for (i = 0; i < dtp->dt_conf.num_online_cpus; i++) { > int cpu = dtp->dt_conf.cpus[i].cpu_id; > char name[16]; > @@ -702,6 +706,8 @@ gmap_create_aggs(dtrace_hdl_t *dtp) > return map_create_error(dtp, name, errno); > > dt_bpf_map_update(dtp->dt_aggmap_fd, &cpu, &fd); > + if (dt_bpf_map_lookup(dtp->dt_aggmap_fd, &cpu, &dtp->dt_aggmap_ids[i]) < 0) > + return -1; > } > > /* Create the agg generation value array. */ > diff --git a/libdtrace/dt_impl.h b/libdtrace/dt_impl.h > index 68fb8ec53..1033154d9 100644 > --- a/libdtrace/dt_impl.h > +++ b/libdtrace/dt_impl.h > @@ -388,6 +388,7 @@ struct dtrace_hdl { > int dt_proc_fd; /* file descriptor for proc eventfd */ > int dt_stmap_fd; /* file descriptor for the 'state' BPF map */ > int dt_aggmap_fd; /* file descriptor for the 'aggs' BPF map */ > + int *dt_aggmap_ids; /* ids for the 'aggN' BPF maps */ > int dt_genmap_fd; /* file descriptor for the 'agggen' BPF map */ > int dt_cpumap_fd; /* file descriptor for the 'cpuinfo' BPF map */ > int dt_usdt_pridsmap_fd; /* file descriptor for the 'usdt_prids' BPF map */ > diff --git a/libdtrace/dt_open.c b/libdtrace/dt_open.c > index 71ee21467..7da4c82cc 100644 > --- a/libdtrace/dt_open.c > +++ b/libdtrace/dt_open.c > @@ -1233,6 +1233,7 @@ dtrace_close(dtrace_hdl_t *dtp) > dt_probe_detach_all(dtp); > > dt_free(dtp, dtp->dt_conf.cpus); > + dt_free(dtp, dtp->dt_aggmap_ids); > > if (dtp->dt_procs != NULL) > dt_proc_hash_destroy(dtp); > -- > 2.43.5 > > > _______________________________________________ > DTrace-devel mailing list > DTrace-devel@oss.oracle.com > https://oss.oracle.com/mailman/listinfo/dtrace-devel