On Wed, May 03, 2017 at 01:31:10AM +1000, Bruce Evans wrote: > > > On Tue, 2 May 2017, Konstantin Belousov wrote: > I also thought of changing the scale when the values get high. The values > would increase slower above about 2G instead of stabilizing at 4G-1. > This is basically floating point and too complicated since nothing would > understand it. > > Which counters wrap faster than a reasonable refresh interval of 1-10 > seconds (which should be shorter if wrapping is a problem)? Things like various counters for pages freed due to a reason can. E.g. freed due to the process exit is the counter which I saw changing fast.
Wire counts might fluctuate relatively quickly, but I think that wiring is slower. Unwiring might be fast. > Style: > - redundant cast. Especially not needed with the commit. Compilers might > warn about this since they don't trust programmers, but don't because > implicit downwards conversions are used often. > - comment not indented > > I would also omit the ifdefs, and rename 'out' to out64, and may rename > 'out*' to val*. Ok. > I just noticed that this sysctl is r/o (I thought I was preserving support > for resetting 64-bit counters using a 32-bit size in my fix in > sysctl_handle_counter_64(). That function has the dubious feature of not > checking the size, so it allows writes of any length (0 to SIZE_MAX, > possibly larger than the user data) to reset the counter to zero.) > > The r/o misfeature goes back to at least FreeBSD-3. 64-bit counters need > resetting less than 32-bit ones, and it is more useful to ever reset them > since they can hold the full counts since boot time, but there is no reason > to limit resetting them now that the low-level code supports it. Is there > already a better atomic reset of all vm stats? I do not see why vmstat counters ever need to be reset. I do not think that truncating the value to present small values to 32bit readers is a reasonable cause. diff --git a/sys/vm/vm_meter.c b/sys/vm/vm_meter.c index 5f4cd46ab1e..b4666a400b2 100644 --- a/sys/vm/vm_meter.c +++ b/sys/vm/vm_meter.c @@ -266,8 +266,27 @@ static SYSCTL_NODE(_vm_stats, OID_AUTO, vm, CTLFLAG_RW, 0, "VM meter vm stats"); SYSCTL_NODE(_vm_stats, OID_AUTO, misc, CTLFLAG_RW, 0, "VM meter misc stats"); +static int +sysctl_handle_vmstat(SYSCTL_HANDLER_ARGS) +{ + uint64_t val; +#ifdef COMPAT_FREEBSD11 + uint32_t val32; +#endif + + val = counter_u64_fetch(*(counter_u64_t *)arg1); +#ifdef COMPAT_FREEBSD11 + if (req->oldlen == sizeof(val32)) { + val32 = val; /* truncate */ + return (SYSCTL_OUT(req, &val32, sizeof(val32))); + } +#endif + return (SYSCTL_OUT(req, &val, sizeof(val))); +} + #define VM_STATS(parent, var, descr) \ - SYSCTL_COUNTER_U64(parent, OID_AUTO, var, CTLFLAG_RD, &vm_cnt.var, descr) + SYSCTL_OID(parent, OID_AUTO, var, CTLTYPE_U64 | CTLFLAG_MPSAFE | \ + CTLFLAG_RD, &vm_cnt.var, 0, sysctl_handle_vmstat, "QU", descr); #define VM_STATS_VM(var, descr) VM_STATS(_vm_stats_vm, var, descr) #define VM_STATS_SYS(var, descr) VM_STATS(_vm_stats_sys, var, descr) _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"