Re: Waiting for bufdaemon

Am 20.01.21 um 11:18 schrieb Konstantin Belousov:
> On Wed, Jan 20, 2021 at 11:02:21AM +0100, Jakob Alvermark wrote:
>> This patch hides the problem for me. The system seems to work better now.
>>
>> No waiting on reboot, and the webcam works better.
> I am curious what do you mean by the above reference to webcam.
> Can you explain it with more details, even if only the impressions?

I should mention, that beside the already discussed timing problem with
bufdaemon, I also have problems with several apps:


After a high system load, several programs only react very slowly (e.g.
Firefox). Several dockable apps from WindowMaker, but also e.g. conky do
not update their windows anymore, they freeze. After some time, Firefox
updates its screen content only after switching back from another window ...

When such frozen programs are killed and restarted, they run normally
again for an indefinite time before they freeze again.

These symptoms completely disappeared, after I patched the Ryzen box as
suggested on 01/17:

diff --git a/sys/x86/tsc.c b/sys/x86/tsc.c
index 85924df98312..5700a8ca98e5 100644
--- a/sys/x86/x86/tsc.c
+++ b/sys/x86/x86/tsc.c
_at__at_ -639,7 +639,7 _at__at_ init_TSC_tc(void)
 	 * on Intel, and MFENCE;RDTSC on AMD.
 	 * - For really old CPUs, just use RDTSC.
 	 */
- if ((cpu_vendor_id == CPU_VENDOR_AMD ||
+ if (false && (cpu_vendor_id == CPU_VENDOR_AMD ||
 	    cpu_vendor_id == CPU_VENDOR_HYGON) &&
 	    CPUID_TO_FAMILY(cpu_id) >= 0x17) {
 		tsc_timecounter.tc_get_timecount = shift > 0 ?


HTH,
Rainer


> 
> I probably going to commit the following patch in the next 24 hours.
> 
> commit 02505d07bca320a638c96918ac9076c6eece2fff
> Author: Konstantin Belousov <kib_at_FreeBSD.org>
> Date:   Wed Jan 20 11:32:21 2021 +0200
> 
>     AMD Zen CPUs: switch TSC timecounter to RDTSCP
>     
>     Reported by:    many
>     MFC after:      1 weel
>     Sponsored by:   The FreeBSD Foundation
> 
> diff --git a/lib/libc/x86/sys/__vdso_gettc.c b/lib/libc/x86/sys/__vdso_gettc.c
> index 7f224f8758cb..7a64f2a0b556 100644
> --- a/lib/libc/x86/sys/__vdso_gettc.c
> +++ b/lib/libc/x86/sys/__vdso_gettc.c
> _at__at_ -125,7 +125,7 _at__at_ struct tsc_selector_tag {
>  };
>  
>  static const struct tsc_selector_tag tsc_selector[] = {
> -	[0] = {				/* Intel or AMD Zen+, LFENCE */
> +	[0] = {				/* Intel, LFENCE */
>  		.ts_rdtsc32 =	rdtsc32_mb_lfence,
>  		.ts_rdtsc_low =	rdtsc_low_mb_lfence,
>  	},
> _at__at_ -164,9 +164,6 _at__at_ tsc_selector_idx(u_int cpu_feature)
>  	do_cpuid(1, p);
>  	cpu_id = p[0];
>  
> -	if (amd_cpu && CPUID_TO_FAMILY(cpu_id) >= 0x17)
> -		return (0);
> -
>  	if (cpu_feature != 0) {
>  		do_cpuid(0x80000000, p);
>  		cpu_exthigh = p[0];
> diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c
> index 85924df98312..de0a1505c2f6 100644
> --- a/sys/x86/x86/tsc.c
> +++ b/sys/x86/x86/tsc.c
> _at__at_ -633,19 +633,12 _at__at_ init_TSC_tc(void)
>  
>  	/*
>  	 * Timecounter implementation selection, top to bottom:
> -	 * - For AMD Zens and newer, use LFENCE;RDTSC.
>  	 * - If RDTSCP is available, use RDTSCP.
>  	 * - If fence instructions are provided (SSE2), use LFENCE;RDTSC
>  	 *   on Intel, and MFENCE;RDTSC on AMD.
>  	 * - For really old CPUs, just use RDTSC.
>  	 */
> -	if ((cpu_vendor_id == CPU_VENDOR_AMD ||
> -	    cpu_vendor_id == CPU_VENDOR_HYGON) &&
> -	    CPUID_TO_FAMILY(cpu_id) >= 0x17) {
> -		tsc_timecounter.tc_get_timecount = shift > 0 ?
> -		    tsc_get_timecount_low_lfence :
> -		    tsc_get_timecount_lfence;
> -	} else if ((amd_feature & AMDID_RDTSCP) != 0) {
> +	if ((amd_feature & AMDID_RDTSCP) != 0) {
>  		tsc_timecounter.tc_get_timecount = shift > 0 ?
>  		    tscp_get_timecount_low : tscp_get_timecount;
>  	} else if ((cpu_feature & CPUID_SSE2) != 0 && mp_ncpus > 1) {