Re: O->A loan

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

the regression shown by yamt3.png seems bigger than i expected.
i guess there are some bugs...

anyway, thanks!

YAMAMOTO Takashi

> The first one is tmpfs (2GB md)
> The other is UFS
> On Mon, 16 Jan 2012, YAMAMOTO Takashi wrote:
> 
>> Date: Mon, 16 Jan 2012 04:04:31 +0000 (UTC)
>> From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>> To: jaimef%mauthesis.com@localhost
>> Cc: chuq%chuq.com@localhost, tech-kern%netbsd.org@localhost
>> Subject: Re: O->A loan
>> 
>> hi,
>>
>> i'm wondering why the following two are this drastically different.
>> was there configuration changes more than flipping DIAGNOSTIC?
>>
>>      http://linbsd.org/yamt.png
>>      http://linbsd.org/yamt3.png
>>
>> YAMAMOTO Takashi
>>
>>> This is the same hardware.
>>> rmind had noticed in the lockstat output that fileassoc was being called
>>> on all unlink() operation. So I am rerunning the tests without fileassoc.
>>>
>>> On Mon, 16 Jan 2012, YAMAMOTO Takashi wrote:
>>>
>>>> Date: Mon, 16 Jan 2012 03:47:48 +0000 (UTC)
>>>> From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>>>> To: jaimef%mauthesis.com@localhost
>>>> Cc: chuq%chuq.com@localhost, tech-kern%netbsd.org@localhost
>>>> Subject: Re: O->A loan
>>>>
>>>> hi,
>>>>
>>>> thanks.
>>>> is this on a different hardware from the previous one?
>>>>
>>>> YAMAMOTO Takashi
>>>>
>>>>>
>>>>> Hello Yamamoto-san
>>>>>
>>>>> I have run dbench on ufs/wapbl with diagnostics disabled.
>>>>> http://linbsd.org/yamt3.png
>>>>>
>>>>>
>>>>> On Thu, 12 Jan 2012, YAMAMOTO Takashi wrote:
>>>>>
>>>>>> Date: Thu, 12 Jan 2012 03:31:59 +0000 (UTC)
>>>>>> From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>>>>>> To: jaimef%mauthesis.com@localhost
>>>>>> Cc: chuq%chuq.com@localhost, tech-kern%netbsd.org@localhost
>>>>>> Subject: Re: O->A loan
>>>>>>
>>>>>> hi,
>>>>>>
>>>>>>> I did not remove DIAGNOSTIC.
>>>>>>> Would you like me to rerun without DIAGNOSTIC?
>>>>>>
>>>>>> yes, please.
>>>>>>
>>>>>> YAMAMOTO Takashi
>>>>>>
>>>>>>> On Thu, 12 Jan 2012, YAMAMOTO Takashi wrote:
>>>>>>>
>>>>>>>> Date: Thu, 12 Jan 2012 03:14:33 +0000 (UTC)
>>>>>>>> From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>>>>>>>> To: jaimef%mauthesis.com@localhost
>>>>>>>> Cc: chuq%chuq.com@localhost, tech-kern%netbsd.org@localhost
>>>>>>>> Subject: Re: O->A loan
>>>>>>>>
>>>>>>>> hi,
>>>>>>>>
>>>>>>>> thanks for benchmark!
>>>>>>>>
>>>>>>>> was it without DIAGNOSTIC?
>>>>>>>>
>>>>>>>> YAMAMOTO Takashi
>>>>>>>>
>>>>>>>>> Hello Yamamoto-san,
>>>>>>>>>
>>>>>>>>> I ran dbench on the same system with yamt-pagecache, yamt-pagecache
>>>>>>>>> without a-o loan, and yamt-pagecache-base3.
>>>>>>>>> http://linbsd.org/yamt.png
>>>>>>>>> The tests were run three times on each kernel and the results were
>>>>>>>>> consistent between reboots/runs.
>>>>>>>>>
>>>>>>>>> Thanks.
>>>>>>>>>
>>>>>>>>> On Tue, 27 Dec 2011, YAMAMOTO Takashi wrote:
>>>>>>>>>
>>>>>>>>>> Date: Tue, 27 Dec 2011 02:53:29 +0000 (UTC)
>>>>>>>>>> From: YAMAMOTO Takashi <yamt%mwd.biglobe.ne.jp@localhost>
>>>>>>>>>> To: chuq%chuq.com@localhost
>>>>>>>>>> Cc: tech-kern%netbsd.org@localhost
>>>>>>>>>> Subject: Re: O->A loan
>>>>>>>>>>
>>>>>>>>>> hi,
>>>>>>>>>>
>>>>>>>>>> i made read with O->A loaning work for easy cases (ie. no locking 
>>>>>>>>>> difficulty)
>>>>>>>>>> on yamt-pagecache branch so that someone interested can benchmark.
>>>>>>>>>>
>>>>>>>>>> YAMAMOTO Takashi
>>>>>>>>>>
>>>>>>>>>>> hi,
>>>>>>>>>>>
>>>>>>>>>>>> On Tue, Nov 29, 2011 at 06:38:27AM +0000, YAMAMOTO Takashi wrote:
>>>>>>>>>>>>> O->A loaned pages installed on the user address space would have 
>>>>>>>>>>>>> a different
>>>>>>>>>>>>> owner than the usual map->entry.uvm_obj.
>>>>>>>>>>>>> although it was not a problem when you wrote this patch, at least 
>>>>>>>>>>>>> some
>>>>>>>>>>>>> non-mechanical changes would be required after the recent locking
>>>>>>>>>>>>> changes in this area.  namely, uvm_map_lock_entry etc now assumes 
>>>>>>>>>>>>> that
>>>>>>>>>>>>> any pages mapped in a map entry belong to either the entry's amap 
>>>>>>>>>>>>> or
>>>>>>>>>>>>> underlying object.
>>>>>>>>>>>>
>>>>>>>>>>>> ok, I didn't think it would be entirely mechanical.  :-)
>>>>>>>>>>>>
>>>>>>>>>>>> what if the O->A loan code also changed the entry's uvm_obj to be 
>>>>>>>>>>>> the vnode
>>>>>>>>>>>> that the pages really belong to?  if the loan range in the amap is 
>>>>>>>>>>>> fully
>>>>>>>>>>>> populated (which it is in this context) then that shouldn't affect 
>>>>>>>>>>>> the
>>>>>>>>>>>> logical contents of the entry, it would just cause anyone locking 
>>>>>>>>>>>> the entry
>>>>>>>>>>>> to also lock the vnode.  if the range of the loan is smaller than 
>>>>>>>>>>>> the
>>>>>>>>>>>> range of the entry, we could split the entry.  do you think that 
>>>>>>>>>>>> would work?
>>>>>>>>>>>
>>>>>>>>>>> it might work, but i have some concerns:
>>>>>>>>>>> - entry fragmentation
>>>>>>>>>>> - the extra uobj reference keeps the file even after unlink
>>>>>>>>>>>
>>>>>>>>>>> YAMAMOTO Takashi
>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> -Chuck