* max memory limits ???
@ 2000-11-22 13:37 BenHanokh Gabriel
2000-11-22 14:11 ` Matti Aarnio
2000-11-25 10:45 ` Raymond Nijssen
0 siblings, 2 replies; 5+ messages in thread
From: BenHanokh Gabriel @ 2000-11-22 13:37 UTC (permalink / raw
To: linux-mm
hi
can some1 explain the memory limits on the 2.4 kernel
- what is the maximum amount of physical memory it supports ?
- what is the limit for user-space apps ?
- what is the limit for kernel ?
- are there any limits on malloc, static-memory, stack-memory ?
- does using HIGHMEM results with performance penalty ?
- anything else ?
please CC me for any answer
regards
Benhanokh Gabriel
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* Re: max memory limits ???
2000-11-22 13:37 BenHanokh Gabriel
@ 2000-11-22 14:11 ` Matti Aarnio
2000-11-22 15:28 ` Stephen C. Tweedie
2000-11-25 10:45 ` Raymond Nijssen
1 sibling, 1 reply; 5+ messages in thread
From: Matti Aarnio @ 2000-11-22 14:11 UTC (permalink / raw
To: BenHanokh Gabriel; +Cc: linux-mm
On Wed, Nov 22, 2000 at 03:37:09PM +0200, BenHanokh Gabriel wrote:
> hi
>
> can some1 explain the memory limits on the 2.4 kernel
>
> - what is the maximum amount of physical memory it supports ?
There are some Alpha systems with 256 GB memory where Linux is
sometimes tested. Those processors support up to several
terabytes of memory (nobody built such maximum machines, though.)
For intel machines limits are different, of course.
(PAE36 supports up to 16*4 GB = 64 GB physical address space,
within which there must be some holes to support e.g. PCI
bus address spaces, and system boot rom, to name a few.)
For intel ia64 -- that is a 64 bit machine, thus it propably
follows Alpha and UltraSPARC model in this regard.
> - what is the limit for user-space apps ?
At 32 bit systems: 3.5 GB with extreme tricks, 3 GB for more usual.
At 64 bit systems -- 2^60 or some such semi-meaningless value.
> - what is the limit for kernel ?
Whatever the hardware supports.
> - are there any limits on malloc, static-memory, stack-memory ?
userspace rules.
> - does using HIGHMEM results with performance penalty ?
Of course, it causes extra mapping operations on machines
needing it to support larger memory (intel PAE36 featured
hardware). User processes can access all what is mapped
into them at the same time -- All programs, kernel included
are limited to 32 bit addresses, but kernel can juggle maps
to reach areas not mapped in its address space at some moment.
> - anything else ?
>
> please CC me for any answer
>
> regards
> Benhanokh Gabriel
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* Re: max memory limits ???
2000-11-22 14:11 ` Matti Aarnio
@ 2000-11-22 15:28 ` Stephen C. Tweedie
0 siblings, 0 replies; 5+ messages in thread
From: Stephen C. Tweedie @ 2000-11-22 15:28 UTC (permalink / raw
To: Matti Aarnio; +Cc: BenHanokh Gabriel, linux-mm
Hi,
On Wed, Nov 22, 2000 at 04:11:04PM +0200, Matti Aarnio wrote:
> > - does using HIGHMEM results with performance penalty ?
>
> Of course, it causes extra mapping operations on machines
> needing it to support larger memory (intel PAE36 featured
> hardware). User processes can access all what is mapped
> into them at the same time -- All programs, kernel included
> are limited to 32 bit addresses, but kernel can juggle maps
> to reach areas not mapped in its address space at some moment.
The other performance implications are:
HIGHMEM currently results in extra copies if you are on Intel and
using a 4G or 64G config, whenever you perform disk IO to memory above
1GB. If you are using the 64G config (PAE36), then the page tables
double in size, occupying more of your cache. Those are likely to be
the two biggest performance costs in enabling highmem in an i686
kernel.
Cheers,
Stephen
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: max memory limits ???
2000-11-22 13:37 BenHanokh Gabriel
2000-11-22 14:11 ` Matti Aarnio
@ 2000-11-25 10:45 ` Raymond Nijssen
1 sibling, 0 replies; 5+ messages in thread
From: Raymond Nijssen @ 2000-11-25 10:45 UTC (permalink / raw
To: linux-mm
>Matti Aarnio <matti.aarnio@zmailer.org> wrote:
>On Wed, Nov 22, 2000 at 03:37:09PM +0200, BenHanokh Gabriel wrote:
>> can some1 explain the memory limits on the 2.4 kernel
>> - what is the limit for user-space apps ?
> At 32 bit systems: 3.5 GB with extreme tricks, 3 GB for more usual.
What are those tricks? Do they involve changing TASK_SIZE ?
And why do programs get mapped at 0x08000000 instead of 0x00001000 ?
This is wasting another 5% of the addressing space.
Please CC me on your reply.
Thanks,
-Raymond
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: max memory limits ???
@ 2000-11-26 10:53 aprasad
0 siblings, 0 replies; 5+ messages in thread
From: aprasad @ 2000-11-26 10:53 UTC (permalink / raw
To: Raymond Nijssen; +Cc: linux-kernel
>Matti Aarnio <matti.aarnio@zmailer.org> wrote:
>On Wed, Nov 22, 2000 at 03:37:09PM +0200, BenHanokh Gabriel wrote:
>> can some1 explain the memory limits on the 2.4 kernel
>> - what is the limit for user-space apps ?
> At 32 bit systems: 3.5 GB with extreme tricks, 3 GB for more
usual.
user space apps will get killed by OOM if its memory required exceeds the
available physical memory+total swapping space.
Regards
Anil
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2000-11-26 10:53 max memory limits ??? aprasad
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2000-11-22 13:37 BenHanokh Gabriel
2000-11-22 14:11 ` Matti Aarnio
2000-11-22 15:28 ` Stephen C. Tweedie
2000-11-25 10:45 ` Raymond Nijssen
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