[PING] Avoid excessive buffer size in libio (was: Re: [PATCH] libio: Always use _IO_BUFSIZE for stream buffers [BZ #4099])

[Florian Weimer]

On 05/19/2016 04:57 PM, Florian Weimer wrote:
> On 03/31/2016 12:14 PM, Florian Weimer wrote:
>> On 03/18/2016 11:52 PM, Roland McGrath wrote:
>>
>>> Whatever the results, they would not IMHO be relevant here.
>>>
>>> POSIX specifies that st_blksize is the "preferred I/O block size for
>>> this
>>> object".  It's the kernel's responsibility to give userland good advice
>>> through this channel.  If there are common buggy kernels that give bad
>>> advice, that is a reason to apply upper and lower limits to the
>>> advice from
>>> the kernel.  But the expectation should be that the kernel gets fixed to
>>> give good advice, and the optimal thing to do with a good kernel is to
>>> follow its advice.
>>>
>>> Since the recommended use of st_blksize in this way is a standard user
>>> feature and not just what stdio's implementation happens to do, there
>>> is an
>>> argument to be made that the limiting of the value should be done in the
>>> *stat functions reported st_blksize values rather than in stdio's use of
>>> them.  (I'm ambivalent about this point.)
>>
>> That's a good point.  I'll try to get feedback from kernel file system
>> developers on this matter.
>
> I wasn't able to get any feedback.  Based on Rich's point about random
> I/O and Roland's earlier suggestion, I'm just capping the reported
> buffer size to 8192 in the attached patch.

Ping?

   <https://sourceware.org/ml/libc-alpha/2016-05/msg00428.html>

Thanks,
Florian