Date: Fri, 9 Dec 2016 17:58:34 +0000 (UTC) From: Gleb Smirnoff <glebius@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r309745 - in head: share/man/man9 sys/kern sys/sys Message-ID: <201612091758.uB9HwYC0087384@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: glebius Date: Fri Dec 9 17:58:34 2016 New Revision: 309745 URL: https://svnweb.freebsd.org/changeset/base/309745 Log: Provide counter_ratecheck(), a MP-friendly substitution to ppsratecheck(). When rated event happens at a very quick rate, the ppsratecheck() is not only racy, but also becomes a performance bottleneck. Together with: rrs, jtl Modified: head/share/man/man9/counter.9 head/sys/kern/subr_counter.c head/sys/sys/counter.h Modified: head/share/man/man9/counter.9 ============================================================================== --- head/share/man/man9/counter.9 Fri Dec 9 17:58:07 2016 (r309744) +++ head/share/man/man9/counter.9 Fri Dec 9 17:58:34 2016 (r309745) @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd March 14, 2016 +.Dd December 8, 2016 .Dt COUNTER 9 .Os .Sh NAME @@ -51,6 +51,8 @@ .Fn counter_u64_fetch "counter_u64_t c" .Ft void .Fn counter_u64_zero "counter_u64_t c" +.Ft int64_t +.Fn counter_ratecheck "struct counter_rate *cr" "int64_t limit" .In sys/sysctl.h .Fn SYSCTL_COUNTER_U64 parent nbr name access ptr descr .Fn SYSCTL_ADD_COUNTER_U64 ctx parent nbr name access ptr descr @@ -128,6 +130,18 @@ value for any moment. Clear the counter .Fa c and set it to zero. +.It Fn counter_ratecheck cr limit +The function is a multiprocessor-friendly version of +.Fn ppsratecheck , +which uses +.Nm +internally. +Returns non-negative value if the rate isn't yet reached during the current +second, and a negative value otherwise. +If the limit was reached on previous second, but was just reset back to zero, +then +.Fn counter_ratecheck +returns number of events since previous reset. .It Fn SYSCTL_COUNTER_U64 parent nbr name access ptr descr Declare a static .Xr sysctl Modified: head/sys/kern/subr_counter.c ============================================================================== --- head/sys/kern/subr_counter.c Fri Dec 9 17:58:07 2016 (r309744) +++ head/sys/kern/subr_counter.c Fri Dec 9 17:58:34 2016 (r309745) @@ -119,3 +119,57 @@ sysctl_handle_counter_u64_array(SYSCTL_H return (0); } + +/* + * MP-friendly version of ppsratecheck(). + * + * Returns non-negative if we are in the rate, negative otherwise. + * 0 - rate limit not reached. + * -1 - rate limit reached. + * >0 - rate limit was reached before, and was just reset. The return value + * is number of events since last reset. + */ +int64_t +counter_ratecheck(struct counter_rate *cr, int64_t limit) +{ + int64_t val; + int now; + + val = cr->cr_over; + now = ticks; + + if (now - cr->cr_ticks >= hz) { + /* + * Time to clear the structure, we are in the next second. + * First try unlocked read, and then proceed with atomic. + */ + if ((cr->cr_lock == 0) && + atomic_cmpset_int(&cr->cr_lock, 0, 1)) { + /* + * Check if other thread has just went through the + * reset sequence before us. + */ + if (now - cr->cr_ticks >= hz) { + val = counter_u64_fetch(cr->cr_rate); + counter_u64_zero(cr->cr_rate); + cr->cr_over = 0; + cr->cr_ticks = now; + } + atomic_store_rel_int(&cr->cr_lock, 0); + } else + /* + * We failed to lock, in this case other thread may + * be running counter_u64_zero(), so it is not safe + * to do an update, we skip it. + */ + return (val); + } + + counter_u64_add(cr->cr_rate, 1); + if (cr->cr_over != 0) + return (-1); + if (counter_u64_fetch(cr->cr_rate) > limit) + val = cr->cr_over = -1; + + return (val); +} Modified: head/sys/sys/counter.h ============================================================================== --- head/sys/sys/counter.h Fri Dec 9 17:58:07 2016 (r309744) +++ head/sys/sys/counter.h Fri Dec 9 17:58:34 2016 (r309745) @@ -59,5 +59,18 @@ uint64_t counter_u64_fetch(counter_u64_t for (int i = 0; i < (n); i++) \ counter_u64_zero((a)[i]); \ } while (0) + +/* + * counter(9) based rate checking. + */ +struct counter_rate { + counter_u64_t cr_rate; /* Events since last second */ + volatile int cr_lock; /* Lock to clean the struct */ + int cr_ticks; /* Ticks on last clean */ + int cr_over; /* Over limit since cr_ticks? */ +}; + +int64_t counter_ratecheck(struct counter_rate *, int64_t); + #endif /* _KERNEL */ #endif /* ! __SYS_COUNTER_H__ */
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201612091758.uB9HwYC0087384>