Date: Wed, 20 Jan 2021 11:37:04 +0100 From: Jakob Alvermark <jakob@alvermark.net> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-current <freebsd-current@freebsd.org> Subject: Re: Waiting for bufdaemon Message-ID: <1c4608c3-6116-c110-236c-3a70967d2edb@alvermark.net> In-Reply-To: <YAgDhJ9/YX29kH2a@kib.kiev.ua> References: <369b3d82-98c5-b31e-6168-4003a042f174@FreeBSD.org> <YAGua8f8G57SbUMT@kib.kiev.ua> <556d40b8-92d7-303e-7d87-ea496d0ca733@FreeBSD.org> <YAG4g7dJbRWM7act@kib.kiev.ua> <ed52f8c1-5f43-b71e-1d56-625e2e064a7e@gwdg.de> <9ae3cc65-193a-39c3-4067-0d42e9f634b0@gwdg.de> <YAO9/cxnbGv5u3Bg@kib.kiev.ua> <adb9d42c-d855-1edf-a57c-9b16aad481b7@gwdg.de> <YAQINMoEi7ysBSD5@kib.kiev.ua> <1d675d77-8bdb-c285-ffa2-28330b839734@alvermark.net> <YAgDhJ9/YX29kH2a@kib.kiev.ua>
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On 1/20/21 11:18 AM, Konstantin Belousov wrote:
> 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 probably going to commit the following patch in the next 24 hours.
>
> commit 02505d07bca320a638c96918ac9076c6eece2fff
> Author: Konstantin Belousov <kib@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
> @@ -125,7 +125,7 @@ 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,
> },
> @@ -164,9 +164,6 @@ 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
> @@ -633,19 +633,12 @@ 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) {
I have a Logitech C270 USB webcam that I use for all the online meetings
now that everyone is working from home. (MS Teams, Google Meet, Slack,
Zoom, whatever...).
It is supported by multimedia/webcamd and has been working mostly fine.
(just some rare, occasional hickups)
When I started to notice the bufdaemon problems, I also noticed the
webcam not behaving as before.
It sometimes took me two or three tries to start the camera when joining
a meeting and once it started my video would freeze sometimes, being
frozen for a minute or so. Sometimes when I noticed that it frooze I
would try to restart it, and again it might take a couple of tries to
get it working again.
With the patch it seems to work better again.
Jakob
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