kern.bufcachepercent

[useche]

Hi Guys,

Today I watched the presentation by Bob Beck about the OpenBSD VFS
hacking where he talked about the buffer cache and how it recently
changed (among many other things). Following his advice, I tried to
increase my buffer cache size with no success. The commands I am
running:

$ sysctl kern.bufcachepercent
kern.bufcachepercent=0
$ sudo sysctl -w kern.bufcachepercent=90
kern.bufcachepercent: 0 -> 90
$ sysctl kern.bufcachepercent
kern.bufcachepercent=0

I read in the 4.6 changelog that his was part of the release.

Am I missing something? Do I have to recompile? Or this is just a bug?

Thanks in advance,
Luis

[Robert-101]

On Tue, 3 Nov 2009 19:34:24 -0500
Luis Useche <useche@...> wrote:

> Hi Guys,
>
> Today I watched the presentation by Bob Beck about the OpenBSD VFS
> hacking where he talked about the buffer cache and how it recently
> changed (among many other things). Following his advice, I tried to
> increase my buffer cache size with no success. The commands I am
> running:
>
> $ sysctl kern.bufcachepercent
> kern.bufcachepercent=0
> $ sudo sysctl -w kern.bufcachepercent=90
> kern.bufcachepercent: 0 -> 90
> $ sysctl kern.bufcachepercent
> kern.bufcachepercent=0
>
> I read in the 4.6 changelog that his was part of the release.
>
> Am I missing something? Do I have to recompile? Or this is just a bug?
>
> Thanks in advance,
> Luis

Wasn't this backed out for the 4.6 freeze?
Too lazy to check the commit messages, so i might be mistaken.
Works fine on -current though.

- Robert

[Bob Beck-4]

2009/11/3 Luis Useche <useche@...>:

>
> I read in the 4.6 changelog that his was part of the release.
>
> Am I missing something? Do I have to recompile? Or this is just a bug?

Yeah you are missing something. Listen to the *whole* presentation and
read the *whole* changelog. This is *not* in 4.6

It is in current.

[useche]

On Tue, Nov 3, 2009 at 11:44 PM, Bob Beck <beck@...> wrote:

> 2009/11/3 Luis Useche <useche@...>:
>
>>
>> I read in the 4.6 changelog that his was part of the release.
>>
>> Am I missing something? Do I have to recompile? Or this is just a bug?
>
> Yeah you are missing something. Listen to the *whole* presentation and
> read the *whole* changelog. This is *not* in 4.6
>
> It is in current.

OK. Sorry for the noise. In any case, this change is in the 4.6
changelog (twice, http://www.openbsd.org/plus46.html):

"Added dynamic buffer cache sizing. The sysctl kern.bufcachepercent
will allow you to specify a high-water mark above 10 percent for use
by the cache. If you run low on memory, the page daemon will reclaim
pages from the buffer cache. "

"Added a kern.bufcachepercent sysctl(8) to allow adjusting the buffer
cache size on a running system."

Moreover it is also in the sysctl(8) manual: "kern.bufcachepercent
               integer       yes"

If all I am saying is wrong, sorry again. I just think this would be
an error in the documentation worth to take into account.

Luis.

[Maurice Janssen-2]

On Wed, Nov 04, 2009 at 10:26:50AM -0500, Luis Useche wrote:

>OK. Sorry for the noise. In any case, this change is in the 4.6
>changelog (twice, http://www.openbsd.org/plus46.html):
>
>"Added dynamic buffer cache sizing. The sysctl kern.bufcachepercent
>will allow you to specify a high-water mark above 10 percent for use
>by the cache. If you run low on memory, the page daemon will reclaim
>pages from the buffer cache. "
>
>"Added a kern.bufcachepercent sysctl(8) to allow adjusting the buffer
>cache size on a running system."

No, three times:
"Backed out all the c2k9 buffer cache changes committed during c2k9."

Maurice

[Bob Beck-3]

I don't know what version of plus46.html you are looking at - but that
text doesnt' appear in any version I look at.

Of course it is in the cvs commit log, but that's not the same thing.
That same commit was backed out before 4.6 - and has since gone back
into current.

2009/11/4 Luis Useche <useche@...>:

> On Tue, Nov 3, 2009 at 11:44 PM, Bob Beck <beck@...> wrote:
>> 2009/11/3 Luis Useche <useche@...>:
>>
>>>
>>> I read in the 4.6 changelog that his was part of the release.
>>>
>>> Am I missing something? Do I have to recompile? Or this is just a bug?
>>
>> Yeah you are missing something. Listen to the *whole* presentation and
>> read the *whole* changelog. This is *not* in 4.6
>>
>> It is in current.
>
> OK. Sorry for the noise. In any case, this change is in the 4.6
> changelog (twice, http://www.openbsd.org/plus46.html):

[useche]

Maurice: Thanks for pointing that out.

Bob: At this point this is probably irrelevant. In any case, I found
it in the officiel webpage http://www.openbsd.org/plus46.html.

Thanks for your help!
Luis



On Wed, Nov 4, 2009 at 10:42 AM, Bob Beck <beck@...> wrote:

> I don't know what version of plus46.html you are looking at - but that
> text doesnt' appear in any version I look at.
>
> Of course it is in the cvs commit log, but that's not the same thing.
> That same commit was backed out before 4.6 - and has since gone back
> into current.
>
> 2009/11/4 Luis Useche <useche@...>:
>> On Tue, Nov 3, 2009 at 11:44 PM, Bob Beck <beck@...> wrote:
>>> 2009/11/3 Luis Useche <useche@...>:
>>>
>>>>
>>>> I read in the 4.6 changelog that his was part of the release.
>>>>
>>>> Am I missing something? Do I have to recompile? Or this is just a bug?
>>>
>>> Yeah you are missing something. Listen to the *whole* presentation and
>>> read the *whole* changelog. This is *not* in 4.6
>>>
>>> It is in current.
>>
>> OK. Sorry for the noise. In any case, this change is in the 4.6
>> changelog (twice, http://www.openbsd.org/plus46.html):