Hi,
On Tue, 17 Jun 2014 09:43:07 +0200
Claudio Jeker <cje...@diehard.n-r-g.com> wrote:
> On Mon, Jun 16, 2014 at 11:35:07AM -0600, Theo de Raadt wrote:
>> > > Followings are our kernel variables' default:
>> > >
>> > > - sb_max: 256K
>> > > - tcbhash_size: 128
>> > > - udbhash_size: 128
>> > >
>> > > These variables are sometime too small for busy server or gateway.
>> > >
>> > > I'd like to modify config(8) to customize these variables without
>> > > recompiling the kernel.
>> >
>> > If we go this route, I would rather have a generic command (such as "set
>> > <kernel variable name> <value>") to change kernel variables.
>> >
>> > The list of said variables would still be restricted to what a given
>> > config(8) knows, to prevent people from tinkering with things they are
>> > not supposed to touch.
>>
>>
>> I quite dislike the direction this is going.
>>
>> It seems like you have found 3 variables which should auto-tune.
>> So why not write kernel code to auto-tune them?
>
> We could replace the hashes with RB trees. I think that would be better
> than having to rehash the list. To tune sb_max we need a way to have
> memory limits so that the socket buffers don't consume all the resources
> and starve the kernel out of memory.
I think resizing the hash tables is better than replacing with RB
tree.
Hash
pros:
- faster
- not so big
- easy to understand and customize(eg. adding lock for parallel)
cons:
- need rehash when growing up
--yasuoka
