Distros generally (I looked at Debian, RHEL5 and SLES11) seem to
enable CONFIG_HIGHPTE for any x86 configuration which has highmem
enabled. This means that the overhead applies even to machines which
have a fairly modest amount of high memory and which therefore do not
really benefit from allocating PTEs in high memory but still pay the
price of the additional mapping operations.
Running kernbench on a 4G box I found that with CONFIG_HIGHPTE=y but
no actual highptes being allocated there was a reduction in system
time used from 59.737s to 55.9s.
With CONFIG_HIGHPTE=y and highmem PTEs being allocated:
Average Optimal load -j 4 Run (std deviation):
Elapsed Time 175.396 (0.238914)
User Time 515.983 (5.85019)
System Time 59.737 (1.26727)
Percent CPU 263.8 (71.6796)
Context Switches 39989.7 (4672.64)
Sleeps 42617.7 (246.307)
With CONFIG_HIGHPTE=y but with no highmem PTEs being allocated:
Average Optimal load -j 4 Run (std deviation):
Elapsed Time 174.278 (0.831968)
User Time 515.659 (6.07012)
System Time 55.9 (1.07799)
Percent CPU 263.8 (71.266)
Context Switches 39929.6 (4485.13)
Sleeps 42583.7 (373.039)
This patch allows the user to control the allocation of PTEs in
highmem from the command line ("userpte=nohigh") but retains the
status-quo as the default.
It is possible that some simple heuristic could be developed which
allows auto-tuning of this option however I don't have a sufficiently
large machine available to me to perform any particularly meaningful
experiments. We could probably handwave up an argument for a threshold
at 16G of total RAM.
Assuming 768M of lowmem we have 196608 potential lowmem PTE
pages. Each page can map 2M of RAM in a PAE-enabled configuration,
meaning a maximum of 384G of RAM could potentially be mapped using
lowmem PTEs.
Even allowing generous factor of 10 to account for other required
lowmem allocations, generous slop to account for page sharing (which
reduces the total amount of RAM mappable by a given number of PT
pages) and other innacuracies in the estimations it would seem that
even a 32G machine would not have a particularly pressing need for
highmem PTEs. I think 32G could be considered to be at the upper bound
of what might be sensible on a 32 bit machine (although I think in
practice 64G is still supported).
It's seems questionable if HIGHPTE is even a win for any amount of RAM
you would sensibly run a 32 bit kernel on rather than going 64 bit.
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
LKML-Reference: <1266403090-20162-1-git-send-email-ian.campbell@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
With VMALLOC_END included in the calculation of MAXMEM (as of
2.6.28) it is no longer correct to also bump __VMALLOC_RESERVE
in reserve_top_address(). Doing so results in needlessly small
lowmem.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <4A71DD2A020000780000D482@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
mm: Pass virtual address to [__]p{te,ud,md}_free_tlb()
Upcoming paches to support the new 64-bit "BookE" powerpc architecture
will need to have the virtual address corresponding to PTE page when
freeing it, due to the way the HW table walker works.
Basically, the TLB can be loaded with "large" pages that cover the whole
virtual space (well, sort-of, half of it actually) represented by a PTE
page, and which contain an "indirect" bit indicating that this TLB entry
RPN points to an array of PTEs from which the TLB can then create direct
entries. Thus, in order to invalidate those when PTE pages are deleted,
we need the virtual address to pass to tlbilx or tlbivax instructions.
The old trick of sticking it somewhere in the PTE page struct page sucks
too much, the address is almost readily available in all call sites and
almost everybody implemets these as macros, so we may as well add the
argument everywhere. I added it to the pmd and pud variants for consistency.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: David Howells <dhowells@redhat.com> [MN10300 & FRV]
Acked-by: Nick Piggin <npiggin@suse.de>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> [s390]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As these are allocated using the page allocator, we need to pass
__GFP_NOTRACK before we add page allocator support to kmemcheck.
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Use phys_addr_t for receiving a physical address argument instead of
unsigned long. This allows fixmap to handle pages higher than 4GB on
x86-32.
Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Impact: new interface (not yet use)
Define reserve_top_address for x86_64; only for later x86 integration.
Signed-off-by: Gustavo F. Padovan <gustavo@las.ic.unicamp.br>
Acked-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Simon Horman reported that gcc-3.4.x crashes when compiling
pgd_prepopulate_pmd() when PREALLOCATED_PMDS == 0 and CONFIG_DEBUG_INFO
is enabled.
Adding an extra check for PREALLOCATED_PMDS == 0 [which is compiled out
by gcc] seems to avoid the problem.
Reported-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Simon Horman <horms@verge.net.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Jan Beulich points out that vmalloc_sync_all() assumes that the
kernel's pmd is always expected to be present in the pgd. The current
pgd construction code will add the pgd to the pgd_list before its pmds
have been pre-populated, thereby making it visible to
vmalloc_sync_all().
However, because pgd_prepopulate_pmd also does the allocation, it may
block and cannot be done under spinlock.
The solution is to preallocate the pmds out of the spinlock, then
populate them while holding the pgd_list lock.
This patch also pulls the pmd preallocation and mop-up functions out
to be common, assuming that the compiler will generate no code for
them when PREALLOCTED_PMDS is 0. Also, there's no need for pgd_ctor
to clear the pgd again, since it's allocated as a zeroed page.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add hooks which are called at pgd_alloc/free time. The pgd_alloc hook
may return an error code, which if non-zero, causes the pgd allocation
to be failed. The hooks may be used to allocate/free auxillary
per-pgd information.
also fix:
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> include/asm/pgalloc.h: In function ‘paravirt_pgd_free':
> include/asm/pgalloc.h:14: error: parameter name omitted
> arch/x86/kernel/entry_64.S: In file included from
> arch/x86/kernel/traps_64.c:51:include/asm/pgalloc.h: In function ‘paravirt_pgd_free':
> include/asm/pgalloc.h:14: error: parameter name omitted
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
fix build failure:
arch/x86/mm/pgtable.c:280: warning: ‘enum fixed_addresses’ declared inside parameter list
arch/x86/mm/pgtable.c:280: warning: its scope is only this definition or declaration, which is probably not what you want
arch/x86/mm/pgtable.c:280: error: parameter 1 (‘idx’) has incomplete type
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In both cases, I went with the 32-bit behaviour.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
All pagetables need fundamentally the same setup and destruction, so
just use the same code for everything.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Make KERNEL_PGD_PTRS common, as previously it was only being defined
for 32-bit.
There are a couple of follow-on changes from this:
- KERNEL_PGD_PTRS was being defined in terms of USER_PGD_PTRS. The
definition of USER_PGD_PTRS doesn't really make much sense on x86-64,
since it can have two different user address-space configurations.
I renamed USER_PGD_PTRS to KERNEL_PGD_BOUNDARY, which is meaningful
for all of 32/32, 32/64 and 64/64 process configurations.
- USER_PTRS_PER_PGD was also defined and was being used for similar
purposes. Converting its users to KERNEL_PGD_BOUNDARY left it
completely unused, and so I removed it.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Zach Amsden <zach@vmware.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Rename (alloc|release)_(pt|pd) to pte/pmd to explicitly match the name
of the appropriate pagetable level structure.
[ x86.git merge work by Mark McLoughlin <markmc@redhat.com> ]
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Common definitions for 3-level pagetable functions.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Common definitions for 2-level pagetable functions.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add a common arch/x86/mm/pgtable.c file for common pagetable functions.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
