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author | Stephane Marchesin <stephane.marchesin@gmail.com> | 2012-03-15 00:39:48 -0700 |
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committer | Stephane Marchesin <stephane.marchesin@gmail.com> | 2012-03-15 00:39:48 -0700 |
commit | 83d5fae85ad9d960c4967a6091b7019cdefac639 (patch) | |
tree | 55dac3b3a913c417368c7e3ad6b35f87cad87812 | |
parent | c79e2d605fa16166adf9103acfde55ebf25c36a7 (diff) |
Small changes.
-rw-r--r-- | linuxgraphicsdrivers.lyx | 33 |
1 files changed, 17 insertions, 16 deletions
diff --git a/linuxgraphicsdrivers.lyx b/linuxgraphicsdrivers.lyx index d0ebe6e..f522b60 100644 --- a/linuxgraphicsdrivers.lyx +++ b/linuxgraphicsdrivers.lyx @@ -709,13 +709,13 @@ The first user of the bus is the CPU. In particular, a peripheral which has the ability to read and write to memory without the CPU intervention is said to be DMA (Direct Memory Access) capable, and the memory transaction is usually called a DMA. - This type of transaction is interesting, because it allows the driver to use - the GPU instead of the CPU to do memory transfers. - Since the CPU doesn't need to actively work any more to achieve those transfers, - and since it allows better asynchronicity between the CPU and the GPU, + This type of transaction is interesting, because it allows the driver to + use the GPU instead of the CPU to do memory transfers. + Since the CPU doesn't need to actively work any more to achieve those transfers +, and since it allows better asynchronicity between the CPU and the GPU, better performance can be attained. - Common uses of DMA include improving the performance of - texture uploads or streaming video. + Common uses of DMA include improving the performance of texture uploads + or streaming video. Today, all graphics processors feature this ability (named DMA bus mastering) which consists in the card requesting and subsequently taking control of the bus for a number of microseconds. @@ -737,11 +737,11 @@ Notice that the DMA capability can be a downside in some cases. For example on real time systems, this means the CPU is unable to access the bus while a DMA transaction is in progress, and since DMA transactions happen asynchronously this can lead to missing a real time scheduling deadline. - Another example is small DMA memory transfers, where the CPU overhead of setting - up the DMA is greater than the gain in asynchronicity and therefore transfers - slow down. - So while DMA has a lot of advantages from a performance viewpoint, - there are situations where it should be avoided. + Another example is small DMA memory transfers, where the CPU overhead of + setting up the DMA is greater than the gain in asynchronicity and therefore + transfers slow down. + So while DMA has a lot of advantages from a performance viewpoint, there + are situations where it should be avoided. \end_layout \begin_layout Section @@ -1441,10 +1441,10 @@ Virtual memory. \lang english In order to simplify programming, it is easier to handle contiguous memory areas. - This is easy to achieve as long as only a small area is needed. - But allocating a bigger memory chunk would require as much contiguous physical - memory which is difficult if not impossible to achieve shortly after bootup - because of memory fragmentation. + It is easy to allocate a small contiguous area, but allocating a bigger + memory chunk would require as much contiguous physical memory which is + difficult if not impossible to achieve shortly after bootup because of + memory fragmentation. Therefore, a mechanism is required to keep the appearance of a contiguous piece of memory to the application while using scattered pieces. @@ -1890,7 +1890,8 @@ clflush \begin_layout Standard \lang english -There are 3 caching modes, usable both through MTRR and PAT on system memory: +There are three caching modes, usable both through MTRRs and PAT on system + memory: \end_layout \begin_layout Itemize |