diff --git a/share/man/man4/hwpmc.4 b/share/man/man4/hwpmc.4 index 77fe4b9a075..806c2ee701c 100644 --- a/share/man/man4/hwpmc.4 +++ b/share/man/man4/hwpmc.4 @@ -416,6 +416,9 @@ The size in kilobytes of each log buffer used by .Nm Ns 's logging function. The default buffer size is 4KB. +.It Va kern.hwpmc.mincount Pq integer, read-write +The minimum sampling rate for sampling mode PMCs. +The default count is 1000 events. .It Va kern.hwpmc.mtxpoolsize Pq integer, read-only The size of the spin mutex pool used by the PMC driver. The default is 32. diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c index 18b8bb1674a..21987c310b9 100644 --- a/sys/dev/hwpmc/hwpmc_mod.c +++ b/sys/dev/hwpmc/hwpmc_mod.c @@ -363,6 +363,14 @@ SYSCTL_INT(_kern_hwpmc, OID_AUTO, threadfreelist_max, CTLFLAG_RW, "maximum number of available thread entries before freeing some"); +/* + * kern.hwpmc.mincount -- minimum sample count + */ +static u_int pmc_mincount = 1000; +SYSCTL_INT(_kern_hwpmc, OID_AUTO, mincount, CTLFLAG_RWTUN, + &pmc_mincount, 0, + "minimum count for sampling counters"); + /* * security.bsd.unprivileged_syspmcs -- allow non-root processes to * allocate system-wide PMCs. @@ -3950,13 +3958,16 @@ pmc_syscall_handler(struct thread *td, void *syscall_args) /* XXX set lower bound on sampling for process counters */ if (PMC_IS_SAMPLING_MODE(mode)) { /* - * Don't permit requested sample rate to be less than 1000 + * Don't permit requested sample rate to be + * less than pmc_mincount. */ - if (pa.pm_count < 1000) - log(LOG_WARNING, - "pmcallocate: passed sample rate %ju - setting to 1000\n", - (uintmax_t)pa.pm_count); - pmc->pm_sc.pm_reloadcount = MAX(1000, pa.pm_count); + if (pa.pm_count < MAX(1, pmc_mincount)) + log(LOG_WARNING, "pmcallocate: passed sample " + "rate %ju - setting to %u\n", + (uintmax_t)pa.pm_count, + MAX(1, pmc_mincount)); + pmc->pm_sc.pm_reloadcount = MAX(MAX(1, pmc_mincount), + pa.pm_count); } else pmc->pm_sc.pm_initial = pa.pm_count; @@ -4474,13 +4485,16 @@ pmc_syscall_handler(struct thread *td, void *syscall_args) if (PMC_IS_SAMPLING_MODE(PMC_TO_MODE(pm))) { /* - * Don't permit requested sample rate to be less than 1000 + * Don't permit requested sample rate to be + * less than pmc_mincount. */ - if (sc.pm_count < 1000) - log(LOG_WARNING, - "pmcsetcount: passed sample rate %ju - setting to 1000\n", - (uintmax_t)sc.pm_count); - pm->pm_sc.pm_reloadcount = MAX(1000, sc.pm_count); + if (sc.pm_count < MAX(1, pmc_mincount)) + log(LOG_WARNING, "pmcsetcount: passed sample " + "rate %ju - setting to %u\n", + (uintmax_t)sc.pm_count, + MAX(1, pmc_mincount)); + pm->pm_sc.pm_reloadcount = MAX(MAX(1, pmc_mincount), + sc.pm_count); } else pm->pm_sc.pm_initial = sc.pm_count; }