Date: Wed, 13 Jul 2022 16:47:36 GMT From: John Baldwin <jhb@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 46b46bb77405 - stable/13 - hwpmc: Permit the minimum sampling count to be set as a sysctl. Message-ID: <202207131647.26DGla70052154@gitrepo.freebsd.org>
next in thread | raw e-mail | index | archive | help
The branch stable/13 has been updated by jhb: URL: https://cgit.FreeBSD.org/src/commit/?id=46b46bb77405c3eaf0dbd0c0c09130f773d88718 commit 46b46bb77405c3eaf0dbd0c0c09130f773d88718 Author: John Baldwin <jhb@FreeBSD.org> AuthorDate: 2022-06-09 18:05:34 +0000 Commit: John Baldwin <jhb@FreeBSD.org> CommitDate: 2022-07-13 16:19:13 +0000 hwpmc: Permit the minimum sampling count to be set as a sysctl. A rarely occurring event (e.g. an event that occurs less than 1000 times during execution of a program) may require a lower minimum threshold than 1000. Replace the hardcoded 1000 with a sysctl that the administrator can use to permit smaller sampling count values. Reviewed by: mhorne, mav Sponsored by: University of Cambridge, Google, Inc. Differential Revision: https://reviews.freebsd.org/D35400 (cherry picked from commit ca341f3cf52f8cb036d93cd611d8f3f5b552ea8e) --- share/man/man4/hwpmc.4 | 3 +++ sys/dev/hwpmc/hwpmc_mod.c | 38 ++++++++++++++++++++++++++------------ 2 files changed, 29 insertions(+), 12 deletions(-) diff --git a/share/man/man4/hwpmc.4 b/share/man/man4/hwpmc.4 index 063313045137..5b3353ff935d 100644 --- a/share/man/man4/hwpmc.4 +++ b/share/man/man4/hwpmc.4 @@ -423,6 +423,9 @@ 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 ac0d542c8a4d..50b4f3bc9d3b 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; }
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?202207131647.26DGla70052154>