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  1. 27 1月, 2011 6 次提交
  3. 21 7月, 2010 2 次提交
  5. 14 2月, 2010 1 次提交
    • A
      x86-64, rwsem: Avoid store forwarding hazard in __downgrade_write · 0d1622d7
      由 Avi Kivity 提交于 
      The Intel Architecture Optimization Reference Manual states that a short
load that follows a long store to the same object will suffer a store
forwading penalty, particularly if the two accesses use different addresses.
Trivially, a long load that follows a short store will also suffer a penalty.

__downgrade_write() in rwsem incurs both penalties:  the increment operation
will not be able to reuse a recently-loaded rwsem value, and its result will
not be reused by any recently-following rwsem operation.

A comment in the code states that this is because 64-bit immediates are
special and expensive; but while they are slightly special (only a single
instruction allows them), they aren't expensive: a test shows that two loops,
one loading a 32-bit immediate and one loading a 64-bit immediate, both take
1.5 cycles per iteration.

Fix this by changing __downgrade_write to use the same add instruction on
i386 and on x86_64, so that it uses the same operand size as all the other
rwsem functions.
Signed-off-by: NAvi Kivity <avi@redhat.com>
LKML-Reference: <1266049992-17419-1-git-send-email-avi@redhat.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      0d1622d7
  7. 19 1月, 2010 1 次提交
    • H
      x86-64, rwsem: 64-bit xadd rwsem implementation · 1838ef1d
      由 H. Peter Anvin 提交于 
      For x86-64, 32767 threads really is not enough.  Change rwsem_count_t
to a signed long, so that it is 64 bits on x86-64.

This required the following changes to the assembly code:

a) %z0 doesn't work on all versions of gcc!  At least gcc 4.4.2 as
   shipped with Fedora 12 emits "ll" not "q" for 64 bits, even for
   integer operands.  Newer gccs apparently do this correctly, but
   avoid this problem by using the _ASM_ macros instead of %z.
b) 64 bits immediates are only allowed in "movq $imm,%reg"
   constructs... no others.  Change some of the constraints to "e",
   and fix the one case where we would have had to use an invalid
   immediate -- in that case, we only care about the upper half
   anyway, so just access the upper half.
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <tip-bafaecd1@git.kernel.org>
      1838ef1d
  9. 14 1月, 2010 1 次提交
    • L
      x86: clean up rwsem type system · 5d0b7235
      由 Linus Torvalds 提交于 
      The fast version of the rwsems (the code that uses xadd) has
traditionally only worked on x86-32, and as a result it mixes different
kinds of types wildly - they just all happen to be 32-bit.  We have
"long", we have "__s32", and we have "int".

To make it work on x86-64, the types suddenly matter a lot more.  It can
be either a 32-bit or 64-bit signed type, and both work (with the caveat
that a 32-bit counter will only have 15 bits of effective write
counters, so it's limited to 32767 users).  But whatever type you
choose, it needs to be used consistently.

This makes a new 'rwsem_counter_t', that is a 32-bit signed type.  For a
64-bit type, you'd need to also update the BIAS values.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <alpine.LFD.2.00.1001121755220.17145@localhost.localdomain>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      5d0b7235
  11. 13 1月, 2010 1 次提交
    • L
      x86-32: clean up rwsem inline asm statements · 59c33fa7
      由 Linus Torvalds 提交于 
      This makes gcc use the right register names and instruction operand sizes
automatically for the rwsem inline asm statements.

So instead of using "(%%eax)" to specify the memory address that is the
semaphore, we use "(%1)" or similar. And instead of forcing the operation
to always be 32-bit, we use "%z0", taking the size from the actual
semaphore data structure itself.

This doesn't actually matter on x86-32, but if we want to use the same
inline asm for x86-64, we'll need to have the compiler generate the proper
64-bit names for the registers (%rax instead of %eax), and if we want to
use a 64-bit counter too (in order to avoid the 15-bit limit on the
write counter that limits concurrent users to 32767 threads), we'll need
to be able to generate instructions with "q" accesses rather than "l".

Since this header currently isn't enabled on x86-64, none of that matters,
but we do want to use the xadd version of the semaphores rather than have
to take spinlocks to do a rwsem. The mm->mmap_sem can be heavily contended
when you have lots of threads all taking page faults, and the fallback
rwsem code that uses a spinlock performs abysmally badly in that case.

[ hpa: modified the patch to skip size suffixes entirely when they are
  redundant due to register operands. ]
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <alpine.LFD.2.00.1001121613560.17145@localhost.localdomain>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
      59c33fa7
  13. 23 10月, 2008 2 次提交
  15. 23 7月, 2008 1 次提交
    • V
      x86: consolidate header guards · 77ef50a5
      由 Vegard Nossum 提交于 
      This patch is the result of an automatic script that consolidates the
format of all the headers in include/asm-x86/.

The format:

1. No leading underscore. Names with leading underscores are reserved.
2. Pathname components are separated by two underscores. So we can
   distinguish between mm_types.h and mm/types.h.
3. Everything except letters and numbers are turned into single
   underscores.
Signed-off-by: NVegard Nossum <vegard.nossum@gmail.com>
      77ef50a5
  17. 17 4月, 2008 1 次提交
  19. 30 1月, 2008 2 次提交
  21. 11 10月, 2007 1 次提交
  23. 08 12月, 2006 1 次提交
  25. 26 9月, 2006 1 次提交
  27. 09 7月, 2006 1 次提交
    • L
      i386: improve and correct inline asm memory constraints · b862f3b0
      由 Linus Torvalds 提交于 
      Use "+m" rather than a combination of "=m" and "m" for improved clarity
and consistency.

This also fixes some inlines that incorrectly didn't tell the compiler
that they read the old value at all, potentially causing the compiler to
generate bogus code.  It appear that all of those potential bugs were
hidden by the use of extra "volatile" specifiers on the data structures
in question, though.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
      b862f3b0
  29. 04 7月, 2006 2 次提交
  31. 30 10月, 2005 1 次提交
  33. 17 4月, 2005 1 次提交
    • L
      Linux-2.6.12-rc2 · 1da177e4
      由 Linus Torvalds 提交于 
      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!
      1da177e4