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# spdk_top {#spdk_top}
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2021-07-27 10:05:23 +00:00
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The spdk_top application is designed to resemble the standard top in that it provides a real-time insights into CPU cores usage by SPDK
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lightweight threads and pollers. Have you ever wondered which CPU core is used most by your SPDK instance? Are you building your own bdev
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or library and want to know if your code is running efficiently? Are your new pollers busy most of the time? The spdk_top application uses
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RPC calls to collect performance metrics and displays them in a report that you can analyze and determine if your code is running efficiently
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so that you can tune your implementation and get more from SPDK.
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Why doesn't the classic top utility work for SPDK? SPDK uses a polled-mode design; a reactor thread running on each CPU core assigned to
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an SPDK application schedules SPDK lightweight threads and pollers to run on the CPU core. Therefore, the standard Linux top utility is
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not effective for analyzing the CPU usage for polled-mode applications like SPDK because it just reports that they are using 100% of the
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CPU resources assigned to them. The spdk_top utility was developed to analyze and report the CPU cycles used to do real work vs just
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polling for work. The utility relies on instrumentation added to pollers to track when they are doing work vs. polling for work. The
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spdk_top utility gets the fine grained metrics from the pollers, analyzes and report the metrics on a per poller, thread and core basis.
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This information enables users to identify CPU cores that are busy doing real work so that they can determine if the application
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needs more or less CPU resources.
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2016-06-23 05:43:48 +00:00
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2021-08-02 12:27:54 +00:00
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## Run spdk_top
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2021-01-26 10:19:53 +00:00
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Before running spdk_top you need to run the SPDK application whose performance you want to analyze using spdk_top.
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Run the spdk_top application
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~~~{.sh}
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./build/bin/spdk_top
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~~~
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## Bottom menu
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Menu at the bottom of SPDK top window shows many options for changing displayed data. Each menu item has a key associated with it in square brackets.
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* Quit - quits the SPDK top application.
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* Switch tab - allows to select THREADS/POLLERS/CORES tabs.
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* Previous page/Next page - scrolls up/down to the next set of rows displayed. Indicator in the bottom-left corner shows current page and number
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of all available pages.
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* Item details - displays details pop-up window for highlighted data row. Selection is changed by pressing UP and DOWN arrow keys.
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* Help - displays help pop-up window.
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## Threads Tab
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The threads tab displays a line item for each spdk thread. The information displayed shows:
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* Thread name - name of SPDK thread.
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* Core - core on which the thread is currently running.
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* Active/Timed/Paused pollers - number of pollers grouped by type on this thread.
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* Idle/Busy - how many microseconds the thread was idle/busy.
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\n
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By pressing ENTER key a pop-up window appears, showing above and a list of pollers running on selected
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thread (with poller name, type, run count and period).
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Pop-up then can be closed by pressing ESC key.
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To learn more about spdk threads see @ref concurrency.
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## Pollers Tab
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The pollers tab displays a line item for each poller. The information displayed shows:
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* Poller name - name of currently selected poller.
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* Type - type of poller (Active/Paused/Timed).
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* On thread - thread on which the poller is running.
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* Run count - how many times poller was run.
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* Period - poller period in microseconds. If period equals 0 then it is not displayed.
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* Status - whether poller is currently Busy (red color) or Idle (blue color).
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\n
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Poller pop-up window can be displayed by pressing ENTER on a selected data row and displays above information.
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Pop-up can be closed by pressing ESC key.
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## Cores Tab
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The cores tab provides insights into how the application is using the CPU cores assigned to it. The information displayed for each core shows:
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* Core - core number.
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* Thread count - number of threads currently running on core.
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* Poller count - total number of pollers running on core.
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* Idle/Busy - how many microseconds core was idle (including time when core ran pollers but did not find any work) or doing actual work.
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* Intr - whether this core is in interrupt mode or not.
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\n
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Pressing ENTER key makes a pop-up window appear, showing above information, along with a list of threads running on selected core. Cores details
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window allows to select a thread and display thread details pop-up on top of it. To close both pop-ups use ESC key.
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2021-08-02 12:27:54 +00:00
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## Help Window
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Help window pop-up can be invoked by pressing H key inside any tab. It contains explanations for each key used inside the spdk_top application.
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