Re: Linux 2.6.29

Ric Wheeler
2009-03-26T00:33:39Z

Bron Gondwana wrote:
> On Wed, Mar 25, 2009 at 04:23:08PM -0700, Linus Torvalds wrote:
>
>> On Wed, 25 Mar 2009, Theodore Tso wrote:
>>
>>>> The problem being that unlike the ratio, there's no sane default value
>>>> that you can at least argue is not _entirely_ pointless.
>>>>
>>> Well, if the maximum time that someone wants to wait for an fsync() to
>>> return is one second, and the RAID array can write 100MB/sec
>>>
>> How are you going to tell the kernel that the RAID array can write
>> 100MB/s?
>>
>> The kernel has no idea.
>>
>
> Not at boot up, but after it's been using the RAID array for a little
> while it could...
>
> Bron (... imagining a tunable "max_fsync_wait_target_centisecs = 100"
> which caused the kernel to notice how long flushes were taking
> and tune its buffer sizes to be approximately right over time )
>
This tuning logic is the core of what Josef Bacik did for the
transaction batching code for ext4....

ric