[Interest] memory fragmentation?

[Atlant Schmidt]

All:

> It can be very easily justified that many to Utf* calls are justified because
> of latency in the I/O system means it happens "for free" while reducing the
> overall latency.

In the "modern world", be a little cautious when you decide what activities can
  overlap with other activities. For example, for many of us in the Linux world
  who are using Flash-based file systems (e.g., UBIfs), there's really no such
  thing as overlapping disk I/O with other activities; all "disk" I/O to the Flash
  file system requires the CPU and will block ordinary interactive priority
  user-level activities that also need the CPU.

It's not like in the old days when you queued an I/O request to a rotating
  magnetic disk and between seek latencies and DMA data transfers, you
  could slip-in a lot of computing. Nowadays, that "disk" I/O may still require
  the CPU.

                                              Atlant

From: interest-bounces+aschmidt=dekaresearch.com at qt-project.org [mailto:interest-bounces+aschmidt=dekaresearch.com at qt-project.org] On Behalf Of Jason H
Sent: Tuesday, August 21, 2012 10:17 AM
To: Tony Rietwyk; interest at qt-project.org
Subject: Re: [Interest] memory fragmentation?

Not true for really large XML. With the all-in-one approach, you have to have the entire document completed. This will create a long pause, and increase latency, and increase memory usage. It can be very easily justified that many to Utf* calls are justified because of latency in the I/O system means it happens "for free" while reducing the overall latency.


Would you prefer an image transcoding server that waited for an image to be completely uploaded and completed, or start receiving the conversion as soon as final blocks or scan lines were available?



________________________________
From: Tony Rietwyk <tony at rightsoft.com.au>
To: interest at qt-project.org
Sent: Monday, August 20, 2012 9:52 PM
Subject: Re: [Interest] memory fragmentation?

...
In the end I chose Qt 4.8.1  QXmlStreamWriter(QString *).   The QByteArray version seemed the logical choice - but since the API only uses QString, each call resulted in temporaries being allocated and disposed.  It seems QString is crying out for an appendLatin1(const char *, int len) that re-allocates the unicode array if necessary, and then does the latin1 conversion without creating a temporary.   Doing a single toUtf8 at the end is also better than calling it a million times.




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