Date: Sun, 29 Oct 2017 20:50:03 +0000 (UTC) From: Ian Lepore <ian@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r325108 - head/sys/amd64/vmm/io Message-ID: <201710292050.v9TKo3j5058456@repo.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: ian Date: Sun Oct 29 20:50:03 2017 New Revision: 325108 URL: https://svnweb.freebsd.org/changeset/base/325108 Log: Improve the performance of the hpet timer in bhyve guests by making the timer frequency a power of two. This changes the frequency from 10 to 16.7 MHz (2 ^ 24 HZ). Using a power of two avoids roundoff errors when doing arithmetic in sbintime_t units. Testing shows this can fix erratic ntpd behavior in guests using the hpet timer (which is the default for multicore guests). Reported by: bsam@ Modified: head/sys/amd64/vmm/io/vhpet.c Modified: head/sys/amd64/vmm/io/vhpet.c ============================================================================== --- head/sys/amd64/vmm/io/vhpet.c Sun Oct 29 20:40:56 2017 (r325107) +++ head/sys/amd64/vmm/io/vhpet.c Sun Oct 29 20:50:03 2017 (r325108) @@ -51,7 +51,7 @@ __FBSDID("$FreeBSD$"); static MALLOC_DEFINE(M_VHPET, "vhpet", "bhyve virtual hpet"); -#define HPET_FREQ 10000000 /* 10.0 Mhz */ +#define HPET_FREQ 16777216 /* 16.7 (2^24) Mhz */ #define FS_PER_S 1000000000000000ul /* Timer N Configuration and Capabilities Register */
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201710292050.v9TKo3j5058456>