Re: Does anyone try kib's Sandy Bridge PCID patch (pcid.2.patch)?

在 2012年1月31日 下午11:28，Konstantin Belousov <kostikbel_at_gmail.com> 写道：
> On Tue, Jan 31, 2012 at 09:23:50AM +0800, Paul Ambrose wrote:
>> ?? 2012??1??31?? ????12:43??Kostik Belousov <kostikbel_at_gmail.com> ??????
>> > On Mon, Jan 30, 2012 at 07:08:13PM +0800, Paul Ambrose wrote:
>> >> ?? 2012??1??30?? ????2:36??Kostik Belousov <kostikbel_at_gmail.com> ??????
>> >> > On Mon, Jan 30, 2012 at 10:15:51AM +0800, Paul Ambrose wrote:
>> >> >> I have two boxes, one is  AMD Athlon 610e 2.4G with FreeBSD-current
>> >> >> patched with pcid.2.patch? It works well without other issue and it
>> >> >> seem the pcid patch
>> >> >> does not affect other part of the kernel. The other one is Sandy
>> >> > Athlons do not have PCID and probably will never implement it. They use
>> >> > other tricks to get similar optimizations, transparently to the OS.
>> >> >
>> >> Just curious, is this AMD similar optimizations
>> >>  Address Space Number (ASN) and Global flag
>> >>                           US Patent 6,604,187.
>> >> http://www.chip-architect.com/news/2003_09_21_Detailed_Architecture_of_AMDs_64bit_Core.html
>> > This and the same-important next item 'The TLB Flush Filter' is what
>> > I referred to.
>> >
>> >> I did not found anything about ASN in the AMD manual
>> > It is a transparent optimization, which does not require any OS support.
>> > Intel PCID is completely different, it shall be explicitely handled by OS.
>> > It is some consequence of the nested pages support, AFAIU.
>> >
>> >>
>> >> >> Bridge i5-2300 with FreeBSD 9 release patched with pcid.1.patch( the
>> >> >> pcid.2.patch seems
>> >> >> dependent on AVX and XSAVE stuffs which is available on -current). But
>> >> >> it hangs up just in a few minutes. I doubt the nvidia-driver which is
>> >> >> not recompiled with
>> >> >> patched kernel is the root, I will check this out  later, but does
>> >> >> anyone meet similar problem?
>> >> > There are two many variations compared to the config I did tested.
>> >> > I do not see anything obvious in the changes between HEAD and stable/9
>> >> > which could be blamed. Nvidia driver might be bigger suspect, but again,
>> >> > I am not aware of anything wrong with it.
>> >> >
>> >> >>
>> >> >> I have two question about the pcid.2.patch
>> >> >
>> >> > Item 2 is clean, I fixed it.
>> >> >
>> >> > For the item 1, I was only able to decipher the proposal to optimize
>> >> > the global shootdown handler to restore the %cr3 with bit 64 set to not
>> >> > invalidate current PCID. Is there some more changes ?
>> >> >
>> >> yes, that is what I meant. I was wondering using another way that each
>> >> process has different
>> >> pcid in each active processor, just as the freebsd mips and powerpc
>> >> uses. But obviously this way
>> >> is more friendly to non-pcid  x86  processor.
>> > Each vmspace (or pmap) has unique PCID with the patch, at least until
>> > PCID space (12bit) is not exhausted. To really exhaust it, you need 4095
>> > processes, so it is unlikely but possible event with the current settings.
>> >
>> Thank you for your explanation. I just disabled nvidia-driver( not
>> load it) , and
>> use "buildworld buildkernel" to test the pcid.1.patch with 9-release,
>> it seems the box reset before
>> completing the buildkernel, the attachment is my kernel config, would
>> you mind try it on
>> 9-release with pcid.1.patch? I will git 10-current a try to see if
>> there is something wrong with my hardware
>
> I just did checkout + buildworld + buildkernel with -j 10 on UFS with
> PCID turned on, everything finished fine. It is up to date HEAD.
>
> sandy% sysctl vm.stats.sys.v_swtch vm.pmap.pcid_save_cnt
> vm.stats.sys.v_swtch: 13743519
> vm.pmap.pcid_save_cnt: 7853519
> I.e. the TLB was not flushed one each second context switch.
>
> Trying the HEAD with the patch is probably easiest way forward.
Unfortunately, I try 10-current(HEAD) with pcid.3.patch in my i5-2300
box,  system panic