Re: [PATCH] fdtable: Eradicate fdarray overflow.

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Vadim Lobanov a écrit :
On Wednesday 11 October 2006 22:19, Eric Dumazet wrote:
Hi Vadim

I find your PAGE_SIZE/4 minimum allocation quite unjustified.

For architectures with 64K PAGE_SIZE, we endup allocating 16K, for poor
tasks that happen to touch a not so high (>= 64) file descriptor...

I would vote for a fixed size, like 1024

In my opinion, always picking 1024 would be highly suboptimal for some architectures (x86-64 in particular -- that's a whole page, just for the fdarray!). If anything, I'd prefer something similar to this pseudo-code:

I was speaking of 1024 bytes.

I was the guy who made fdset going from PAGE_SIZE to 64 bytes (L1_CACHE_BYTES if you dare), I wont be the guy responsible for a reverse path on fdtable :)

That is replace your (PAGE_SIZE/4)  by 1024, wich was you probably meant
No archi has a smaller page, so no need to play with min_t() macro...


#define FDTABLE_MIN min_t(uint, PAGE_SIZE / 4 / sizeof(struct file *), 1024)
...
nr /= FDTABLE_MIN;
nr = roundup_pow_of_two(nr + 1);
nr *= FDTABLE_MIN;

gcc should be smart enough to optimize that expression into a single constant. At least it did (version 4.1.0) in my quick test here.

Eric

Let me know what you think. Please don't just go radio-silent on me. ;)


radio-silent ? well, it seems I already sent you many mails about your patches :)

Eric

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