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  1. 02 9月, 2014 2 次提交
    • P
      Merge remote-tracking branch 'remotes/spice/tags/pull-spice-20140902-1' into staging · 30eaca3a
      由 Peter Maydell 提交于 
      sanity check for qxl, minor spice display channel tweak.

# gpg: Signature made Tue 02 Sep 2014 09:53:39 BST using RSA key ID D3E87138
# gpg: Good signature from "Gerd Hoffmann (work) <kraxel@redhat.com>"
# gpg:                 aka "Gerd Hoffmann <gerd@kraxel.org>"
# gpg:                 aka "Gerd Hoffmann (private) <kraxel@gmail.com>"

* remotes/spice/tags/pull-spice-20140902-1:
  spice: use console index as display id
  qxl-render: add more sanity checks
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
      30eaca3a
    • X
      implementing victim TLB for QEMU system emulated TLB · 88e89a57
      由 Xin Tong 提交于 
      QEMU system mode page table walks are expensive. Taken by running QEMU
qemu-system-x86_64 system mode on Intel PIN , a TLB miss and walking a
4-level page tables in guest Linux OS takes ~450 X86 instructions on
average.

QEMU system mode TLB is implemented using a directly-mapped hashtable.
This structure suffers from conflict misses. Increasing the
associativity of the TLB may not be the solution to conflict misses as
all the ways may have to be walked in serial.

A victim TLB is a TLB used to hold translations evicted from the
primary TLB upon replacement. The victim TLB lies between the main TLB
and its refill path. Victim TLB is of greater associativity (fully
associative in this patch). It takes longer to lookup the victim TLB,
but its likely better than a full page table walk. The memory
translation path is changed as follows :

Before Victim TLB:
1. Inline TLB lookup
2. Exit code cache on TLB miss.
3. Check for unaligned, IO accesses
4. TLB refill.
5. Do the memory access.
6. Return to code cache.

After Victim TLB:
1. Inline TLB lookup
2. Exit code cache on TLB miss.
3. Check for unaligned, IO accesses
4. Victim TLB lookup.
5. If victim TLB misses, TLB refill
6. Do the memory access.
7. Return to code cache

The advantage is that victim TLB can offer more associativity to a
directly mapped TLB and thus potentially fewer page table walks while
still keeping the time taken to flush within reasonable limits.
However, placing a victim TLB before the refill path increase TLB
refill path as the victim TLB is consulted before the TLB refill. The
performance results demonstrate that the pros outweigh the cons.

some performance results taken on SPECINT2006 train
datasets and kernel boot and qemu configure script on an
Intel(R) Xeon(R) CPU  E5620  @ 2.40GHz Linux machine are shown in the
Google Doc link below.

https://docs.google.com/spreadsheets/d/1eiItzekZwNQOal_h-5iJmC4tMDi051m9qidi5_nwvH4/edit?usp=sharing

In summary, victim TLB improves the performance of qemu-system-x86_64 by
11% on average on SPECINT2006, kernelboot and qemu configscript and with
highest improvement of in 26% in 456.hmmer. And victim TLB does not result
in any performance degradation in any of the measured benchmarks. Furthermore,
the implemented victim TLB is architecture independent and is expected to
benefit other architectures in QEMU as well.

Although there are measurement fluctuations, the performance
improvement is very significant and by no means in the range of
noises.
Signed-off-by: NXin Tong <trent.tong@gmail.com>
Message-id: 1407202523-23553-1-git-send-email-trent.tong@gmail.com
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
      88e89a57
  3. 01 9月, 2014 37 次提交
  5. 30 8月, 2014 1 次提交
    • P
      Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging · 988f4636
      由 Peter Maydell 提交于 
      Block pull request

# gpg: Signature made Fri 29 Aug 2014 17:25:58 BST using RSA key ID 81AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>"
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>"

* remotes/stefanha/tags/block-pull-request: (35 commits)
  quorum: Fix leak of opts in quorum_open
  blkverify: Fix leak of opts in blkverify_open
  nfs: Fix leak of opts in nfs_file_open
  curl: Don't deref NULL pointer in call to aio_poll.
  curl: Allow a cookie or cookies to be sent with http/https requests.
  virtio-blk: allow drive_del with dataplane
  block: acquire AioContext in do_drive_del()
  linux-aio: avoid deadlock in nested aio_poll() calls
  qemu-iotests: add multiwrite test cases
  block: fix overlapping multiwrite requests
  nbd: Follow the BDS' AIO context
  block: Add AIO context notifiers
  nbd: Drop nbd_can_read()
  sheepdog: fix a core dump while do auto-reconnecting
  aio-win32: add support for sockets
  qemu-coroutine-io: fix for Win32
  AioContext: introduce aio_prepare
  aio-win32: add aio_set_dispatching optimization
  test-aio: test timers on Windows too
  AioContext: export and use aio_dispatch
  ...
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
      988f4636