On Sun, Apr 20, 2008 at 02:47:17PM +0200, Willy Tarreau wrote:A good argument for keeping the default 8k and letting people who know what they are doing, or think they do, test their system for 4k operation. Embedded systems typically have far better defined loads than servers or desktops, and are less likely to have different behavior change the stack requirements. That doesn't mean they do less, just that the load is usually better characterized....
I certainly can understand that reducing memory footprint is useful, but
if we want wider testing of 4k stacks, considering they may fail in error
path in complex I/O environment, it's not likely during -rc kernels that
we'll detect problems, and if we push them down the throat of users in a
stable release, of course they will thank us very much for crashing their
NFS servers in production during peak hours.
I've seen many bugs in error paths in the kernel and fixed quite a few of them - and stack problems were not a significant part of them.
There are so many possible bugs (that also occur in practice) that singling out stack usage won't gain much.
I have nothing against changing the default setting to 4k provided that
it is easy to get back to the save setting (ie changing a config option,
or better, a cmdline parameter). I just don't agree with the idea of
forcing users to swim in the sh*t, it only brings bad reputation to
Linux.
...
What actually brings bad reputation is shipping a 4k option that is known to break under some circumstances.
And history has shown that as long as 8k stacks are available on i386 some problems will not get fixed. 4k stacks are available as an option on i386 for more than 4 years, and at about as long we know that there are some setups (AFAIK all that might still be present seem to include XFS) that are known to not work reliably with 4k stacks.
If we go after stability and reputation, we have to make a decision whether we want to get 4k stacks on 32bit architectures with 4k page size unconditionally or not at all. That's the way that gets the maximal number of bugs shaken out [1] for all supported configurations before they would hit a stable kernel.