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From:Michael Widenius Date:January 29 2000 1:13pm
Subject:Re: Irrelevant ...mmap() VS read()
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>>>>> "Mathijs" == Mathijs Brands <mathijs@stripped> writes:

<cut>

Mathijs> What about tables bigger than 2 GB? Does MySQL use the increased
> addressingspace
Mathijs> on a 64 bit architecture?
>> 
>> Yes;  MySQL can handle big files if the underlaying OS supports it.
>> 
>> The new RAID option can expand the barrier on 32 bit systems, but this
>> is still in testing!

Mathijs> I was talking about mmap. Solaris i86 will only let me mmap a maximum of 2 GB
> (one big
Mathijs> chunk) and the same goes for FreeBSD. So if a single table contains more than
> 2 GB of
Mathijs> data, it cannot be mmap-ed in one piece. This is what I meant.

Currently the code in MySQL that uses memmap assumes it can mmap
everything in one hunk.  If this doesn't work it will fallback to
normal read/write.

Anyway, I think it's on Solaris you can see the biggest improvements
when using mmap as all read/writes are done with memmap (or so I have
been told).

I actually don't know how mmap works on 64 bit architectures;  If one
can allocate bigger hunks than 2G there, there is no reason why it
wouldn't work with MySQL.

Mathijs> If I assume you thought I was referring to the size of files, then the RAID
> remark
Mathijs> suddenly starts to make sense :)

Sorry for the confusion; Yes, that was what I thought

Regards,
Monty
Thread
Irrelevant ...mmap() VS read()Mark Papadakis9 Jan
  • Re: Irrelevant ...mmap() VS read()Sasha Pachev10 Jan
    • Re: Irrelevant ...mmap() VS read()elble10 Jan
      • Re: Irrelevant ...mmap() VS read()Michael Widenius26 Jan
        • Re: Irrelevant ...mmap() VS read()Mathijs Brands27 Jan
          • Re: Irrelevant ...mmap() VS read()Michael Widenius28 Jan
            • Re: Irrelevant ...mmap() VS read()Mathijs Brands29 Jan
              • Re: Irrelevant ...mmap() VS read()Michael Widenius29 Jan
    • Re: Irrelevant ...mmap() VS read()Mike Wexler10 Jan
  • Irrelevant ...mmap() VS read()Michael Widenius11 Jan