Re: [PATCH 9/11] Panic delay fix

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Alan wrote:
??? I fail to see the code bloat and also the fast paths. Which fast paths use udelay?

IDE on several platforms has performance critical paths that use
ndelay(400) or failing that udelay(1)

Ok, I buy that. A 486DX / 33 Mhz processor takes 10 cycles to issue a CALL / RET pair. This is about 300ns. Is there an issue with being too early to issue I/O operations or too late?

If it is too early, then we have lost 10 cycles of processor time per udelay, which considering the antiquity of this piece of hardware, seems acceptable.

If it is too late, then there could be a real issue on older machines. But I fail to see how such careful timing can be done at this granularity on such hardware without well tweaked assembly code. A suboptimal compile output could easily throw you off by just as much, sticking a little bit of arithmetic before and after the delay.

Zach
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux