Large memory support

[Brad Fitzpatrick]

Jason,

I have access to an Opteron right now, but I haven't done extensive
testing on it past building it.  I'll try and work on that.

What would help, though, is if you could get me:

-- a test script to fill up memcached with 5GB of data.  (or hell, this is
   like 10 lines, so I could do it)

-- a patch to change things to size_t (or void* or whatever's appropriate)

Then I'll test it before/after and review other changes and get it
committed.  I don't want to commit without personally testing, though.

So unsigned int is really just 32-bits on 64 bit archs?  Can anybody point
me at a reference to what types map to on different archs?

- Brad


On Wed, 18 Feb 2004, Jason Titus wrote:

> Actually, this was on RedHat Enterprise Linux 64 on a dual Opteron system.  No matter what I entered as a memory size, it listed 2GB as maxbytes in STATS.  When I added more records after it reached 1.9GB it would start tossing things.
>
> When I replaced the unsigned ints with unsigned long longs, it would grow past 2GB.
>
> Seems like switching to size_t would be the best path.  What do you think?
>
> Jason
>
> p.s. - Our goal is to have a ~5GB cache with an entire database.  We want to disable expiration (i.e. nothing getting removed out of the cache) and have the cache be the definitive read only source.  It would have a syncing process to keep it up to date with any changes.
>
> -----Original Message-----
> From: Brad Fitzpatrick [mailto:brad@danga.com]
> Sent: Wed 2/18/2004 9:37 PM
> To: Jason Titus
> Cc: memcached@lists.danga.com
> Subject: Re: Large memory support
>
> Jason,
>
> I've built and run memcached on 64-bit machines.
>
> On a 32-bit machine you won't be able to store more memory than your
> operating system is giving you address space for.  (Not sure if
> your OS is giving you a 2G/2G, 3G/1G, or 3.5G/0.5G split)
>
> I assume you're on 32-bit?  Otherwise, isn't an "unsigned long" just a
> uint64 on 64-bi machines?  Or should we be using void* somewhere we're
> using unsigned int?
>
> Let me know your OS, arch, and the contents of "stats maps" (if on Linux):
>
> $ telnet localhost 11211
> Trying 127.0.0.1...
> Connected to localhost.
> Escape character is '^]'.
> stats maps
> 08048000-08050000 r-xp 00000000 03:03 2167117    /usr/local/bin/memcached-1.1.10pre2
> 08050000-08051000 rw-p 00008000 03:03 2167117    /usr/local/bin/memcached-1.1.10pre2
> 08051000-09c02000 rwxp 00000000 00:00 0
> 40000000-40011000 r-xp 00000000 03:03 165006     /lib/ld-2.3.1.so
> 40011000-40012000 rw-p 00011000 03:03 165006     /lib/ld-2.3.1.so
> 40017000-4011f000 r-xp 00000000 03:03 165009     /lib/libc-2.3.1.so
> 4011f000-40125000 rw-p 00107000 03:03 165009     /lib/libc-2.3.1.so
> 40125000-40128000 rw-p 00000000 00:00 0
> 40128000-40131000 r-xp 00000000 03:03 165014     /lib/libnss_compat-2.3.1.so
> 40131000-40132000 rw-p 00009000 03:03 165014     /lib/libnss_compat-2.3.1.so
> 40132000-40142000 r-xp 00000000 03:03 165013     /lib/libnsl-2.3.1.so
> 40142000-40143000 rw-p 00010000 03:03 165013     /lib/libnsl-2.3.1.so
> 40143000-80946000 rw-p 00000000 00:00 0
> bfffc000-c0000000 rwxp ffffd000 00:00 0
> END
>
>
> - Brad
>
>
> On Wed, 18 Feb 2004, Jason Titus wrote:
>
> > Looks like we just stumbled onto some 32 bit limits in memcached.  Just
> > wondering how you guys want to deal with supporting >2GB per cache.  We
> > have experimented with switching some of the unsigned ints into unsigned
> > long longs and it seemed to work (>4GB seemed ok.  No thorough testing
> > yet though).  A cleaner solution might be adjusting the memory related
> > variables to size_t or some such so that they work well on 32 and 64 bit
> > systems.
> >
> > What makes the most sense to you folks?
> >
> > Jason
> >
> >
>
>