Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>'1 to 1.5 times the number of cores' - this appears to be OS/langauge dependent. On Windows/C++, for example, with large numbers of CPU-intensive tasks, the optimum seems to be much more than twice the number of cores with the performance spread very small. If such environments, it seems you may as well just allocate 64 threads on a pool and not bother with the number of cores.</p> <p>'query/query-ack and response/response - ack model, time must not be wasted in I/O waiting states' - this is unavoidable with such protocols with the high latency of most networks. The delay is enforced by the 'ping-pong' protocol &amp; so there will, inevitably be an I/O wait. Async I/O just moves this wait into the kernel - it's still there!</p> <p>'large requirement for dynamic memory, its better to go with greater number of processes than threads' - not really. 'large requirement for dynamic memory' usually means that large data buffers are going to be moved about. Large buffers can only be efficiently moved around by reference. This is very easy and quick between threads because of the shared memory space. With processes, you are stuck with awkward and slow inter-process comms.</p> <p>'Determining number of threads to have in our application' - well, so difficult on several fronts. Given an unknown architecture, design. language and OS, the only advice I have is to try and make everything as flexible and configurable as you reasonably can. If you have a thread pool, make its size a run-time parameter you can tweak. If you have an object pool, try to design it so that you can change its depth. Have some default values that work on your test boxes and then, at installation or while running, you can make any specific changes and tweaks for a particular system.</p> <p>The other thing with flexible/configurable designs is that you can, at test time, tweak away and fix many of the incorrect decisions, assumptions and guesstimates made by architects, designers, developers and, most of all, customers </p>
    singulars
    1. This table or related slice is empty.
    1. POSelecting number of threads in a multiprocess multiprocessor environment
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USMartin James
    1. USMartin James
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POSelecting number of threads in a multiprocess multiprocessor environment
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COThanks Martin.. But why does OS have a role in it ?? Is it because the final order of execution of instruction (scheduling, etc) depend on OS ? I guessed that the pipe lining and out of order execution were properties of hardware threads .. Please corret me if I am wrong ..
      singulars
      1. PO
      1. USAnerudhan Gopal
    2. COThe OS underlies the interface. Inevitably, peformance differences will surface. One of them is the scheduling algorithm. The final order of thread dispatching depends on the OS, yes. Pipe lining and out of order execution are hardware optimizations, yes.
      singulars
      1. PO
      1. USMartin James
    3. COTHanks once again.. Think I the best way forward is experimenting with an open mind.. :)
      singulars
      1. PO
      1. USAnerudhan Gopal
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload