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Commits on Dec 15, 2009
  1. nommu: fix malloc performance by adding uninitialized flag

    Jie Zhang authored committed
    The NOMMU code currently clears all anonymous mmapped memory.  While this
    is what we want in the default case, all memory allocation from userspace
    under NOMMU has to go through this interface, including malloc() which is
    allowed to return uninitialized memory.  This can easily be a significant
    performance penalty.  So for constrained embedded systems were security is
    irrelevant, allow people to avoid clearing memory unnecessarily.
    
    This also alters the ELF-FDPIC binfmt such that it obtains uninitialised
    memory for the brk and stack region.
    
    Signed-off-by: Jie Zhang <jie.zhang@analog.com>
    Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
    Signed-off-by: Mike Frysinger <vapier@gentoo.org>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Acked-by: Paul Mundt <lethal@linux-sh.org>
    Acked-by: Greg Ungerer <gerg@snapgear.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Commits on Jan 8, 2009
  1. @pmundt

    NOMMU: Make mmap allocation page trimming behaviour configurable.

    pmundt authored David Howells committed
    NOMMU mmap allocates a piece of memory for an mmap that's rounded up in size to
    the nearest power-of-2 number of pages.  Currently it then discards the excess
    pages back to the page allocator, making that memory available for use by other
    things.  This can, however, cause greater amount of fragmentation.
    
    To counter this, a sysctl is added in order to fine-tune the trimming
    behaviour.  The default behaviour remains to trim pages aggressively, while
    this can either be disabled completely or set to a higher page-granular
    watermark in order to have finer-grained control.
    
    vm region vm_top bits taken from an earlier patch by David Howells.
    
    Signed-off-by: Paul Mundt <lethal@linux-sh.org>
    Signed-off-by: David Howells <dhowells@redhat.com>
    Tested-by: Mike Frysinger <vapier.adi@gmail.com>
  2. NOMMU: Make VMAs per MM as for MMU-mode linux

    David Howells authored
    Make VMAs per mm_struct as for MMU-mode linux.  This solves two problems:
    
     (1) In SYSV SHM where nattch for a segment does not reflect the number of
         shmat's (and forks) done.
    
     (2) In mmap() where the VMA's vm_mm is set to point to the parent mm by an
         exec'ing process when VM_EXECUTABLE is specified, regardless of the fact
         that a VMA might be shared and already have its vm_mm assigned to another
         process or a dead process.
    
    A new struct (vm_region) is introduced to track a mapped region and to remember
    the circumstances under which it may be shared and the vm_list_struct structure
    is discarded as it's no longer required.
    
    This patch makes the following additional changes:
    
     (1) Regions are now allocated with alloc_pages() rather than kmalloc() and
         with no recourse to __GFP_COMP, so the pages are not composite.  Instead,
         each page has a reference on it held by the region.  Anything else that is
         interested in such a page will have to get a reference on it to retain it.
         When the pages are released due to unmapping, each page is passed to
         put_page() and will be freed when the page usage count reaches zero.
    
     (2) Excess pages are trimmed after an allocation as the allocation must be
         made as a power-of-2 quantity of pages.
    
     (3) VMAs are added to the parent MM's R/B tree and mmap lists.  As an MM may
         end up with overlapping VMAs within the tree, the VMA struct address is
         appended to the sort key.
    
     (4) Non-anonymous VMAs are now added to the backing inode's prio list.
    
     (5) Holes may be punched in anonymous VMAs with munmap(), releasing parts of
         the backing region.  The VMA and region structs will be split if
         necessary.
    
     (6) sys_shmdt() only releases one attachment to a SYSV IPC shared memory
         segment instead of all the attachments at that addresss.  Multiple
         shmat()'s return the same address under NOMMU-mode instead of different
         virtual addresses as under MMU-mode.
    
     (7) Core dumping for ELF-FDPIC requires fewer exceptions for NOMMU-mode.
    
     (8) /proc/maps is now the global list of mapped regions, and may list bits
         that aren't actually mapped anywhere.
    
     (9) /proc/meminfo gains a line (tagged "MmapCopy") that indicates the amount
         of RAM currently allocated by mmap to hold mappable regions that can't be
         mapped directly.  These are copies of the backing device or file if not
         anonymous.
    
    These changes make NOMMU mode more similar to MMU mode.  The downside is that
    NOMMU mode requires some extra memory to track things over NOMMU without this
    patch (VMAs are no longer shared, and there are now region structs).
    
    Signed-off-by: David Howells <dhowells@redhat.com>
    Tested-by: Mike Frysinger <vapier.adi@gmail.com>
    Acked-by: Paul Mundt <lethal@linux-sh.org>
Commits on Sep 27, 2006
  1. [PATCH] NOMMU: Make futexes work under NOMMU conditions

    David Howells authored Linus Torvalds committed
    Make futexes work under NOMMU conditions.
    
    This can be tested by running this in one shell:
    
    	#define SYSERROR(X, Y) \
    		do { if ((long)(X) == -1L) { perror(Y); exit(1); }} while(0)
    
    	int main()
    	{
    		int shmid, tmp, *f, n;
    
    		shmid = shmget(23, 4, IPC_CREAT|0666);
    		SYSERROR(shmid, "shmget");
    
    		f = shmat(shmid, NULL, 0);
    		SYSERROR(f, "shmat");
    
    		n = *f;
    		printf("WAIT: %p{%x}\n", f, n);
    		tmp = futex(f, FUTEX_WAIT, n, NULL, NULL, 0);
    		SYSERROR(tmp, "futex");
    		printf("WAITED: %d\n", tmp);
    
    		tmp = shmdt(f);
    		SYSERROR(tmp, "shmdt");
    
    		exit(0);
    	}
    
    And then this in the other shell:
    
    	#define SYSERROR(X, Y) \
    		do { if ((long)(X) == -1L) { perror(Y); exit(1); }} while(0)
    
    	int main()
    	{
    		int shmid, tmp, *f;
    
    		shmid = shmget(23, 4, IPC_CREAT|0666);
    		SYSERROR(shmid, "shmget");
    
    		f = shmat(shmid, NULL, 0);
    		SYSERROR(f, "shmat");
    
    		(*f)++;
    		printf("WAKE: %p{%x}\n", f, *f);
    		tmp = futex(f, FUTEX_WAKE, 1, NULL, NULL, 0);
    		SYSERROR(tmp, "futex");
    		printf("WOKE: %d\n", tmp);
    
    		tmp = shmdt(f);
    		SYSERROR(tmp, "shmdt");
    
    		exit(0);
    	}
    
    The first program will set up a SYSV IPC SHM segment and wait on a futex in it
    for the number at the start to change.  The program will increment that number
    and wake the first program up.  This leads to output of the form:
    
    	SHELL 1			SHELL 2
    	=======================	=======================
    	# /dowait
    	WAIT: 0xc32ac000{0}
    				# /dowake
    				WAKE: 0xc32ac000{1}
    	WAITED: 0		WOKE: 1
    
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>
  2. [PATCH] NOMMU: Add docs about shared memory

    David Howells authored Linus Torvalds committed
    Add documentation about using shared memory in NOMMU mode.
    
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>
  3. [PATCH] NOMMU: Make mremap() partially work for NOMMU kernels

    David Howells authored Linus Torvalds committed
    Make mremap() partially work for NOMMU kernels.  It may resize a VMA provided
    that it doesn't exceed the size of the slab object in which the storage is
    allocated that the VMA refers to.  Shareable VMAs may not be resized.
    
    Moving VMAs (as permitted by MREMAP_MAYMOVE) is not currently supported.
    
    This patch also makes use of the fact that the VMA list is now ordered to cut
    it short when possible.
    
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>
  4. [PATCH] NOMMU: Implement /proc/pid/maps for NOMMU

    David Howells authored Linus Torvalds committed
    Implement /proc/pid/maps for NOMMU by reading the vm_area_list attached to
    current->mm->context.vmlist.
    
    Signed-off-by: David Howells <dhowells@redhat.com>
    Signed-off-by: Andrew Morton <akpm@osdl.org>
    Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Commits on Apr 16, 2005
  1. Linux-2.6.12-rc2

    Linus Torvalds authored
    Initial git repository build. I'm not bothering with the full history,
    even though we have it. We can create a separate "historical" git
    archive of that later if we want to, and in the meantime it's about
    3.2GB when imported into git - space that would just make the early
    git days unnecessarily complicated, when we don't have a lot of good
    infrastructure for it.
    
    Let it rip!
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