can a bottom half be scheduled by another BH ??
Hi Group, I am a bit unclear if, I could schedule another BH while I am already running in a BH ? For example, if I am running in a SOFT IRQ, can I schedule a tasklet from there ?? Thanks, Vishwas S
Yes you can, infact network subsystem softirq are reactive so it can run again. however, reactivated softirq are not immediately process but until kernel handles the pending softirqs because it might introduce latency in user-space. And for better performance, when pending BH grows excessively then family of kernel threads are wakes up to handle the load. On 27-Sep-2013, at 4:44 PM, Vishwas Srivastava (vishsriv) <vishsriv@cisco.com> wrote:
Hi Group, I am a bit unclear if, I could schedule another BH while I am already running in a BH ? For example, if I am running in a SOFT IRQ, can I schedule a tasklet from there ??
Thanks, Vishwas S
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On Oct 3, 2013 8:28 PM, "sujan dutta" <stoned.seven@gmail.com> wrote:
Yes you can, infact network subsystem softirq are reactive so it can run
again.
however, reactivated softirq are not immediately process but until kernel handles the pending softirqs because it might introduce latency in user-space. And for better performance, when pending BH grows excessively then family of kernel threads are wakes up to handle the load. Family of threads mentioned here is called ksoftirqd. Linux uses the ksoftirqd as the general solution to schedule softirq's to run before next interrupt and by putting them under scheduler control. Also this prevents consecutive softirq's from monopolizing the CPU. This also has the effect that the priority of ksoftirq needs to be considered when running very CPU-intensive applications and networking to get the proper balance of softirq/user balance. Increasing ksoftirq priority to 0 (eventually more) is reported to cure problems with low network performance at high CPU load. I think softirq calling itself is a problem which is delicately managed by linux kernel developers and how to improve the code and logic is an active field where you can contribute.
On 27-Sep-2013, at 4:44 PM, Vishwas Srivastava (vishsriv) < vishsriv@cisco.com> wrote:
Hi Group, I am a bit unclear if, I could schedule another BH while I am already running in a BH ? For example, if I am running in a SOFT IRQ, can I schedule a tasklet from there ??
Thanks, Vishwas S
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thanks a lot to all of you for the help. Vishwas S On Thu, Oct 3, 2013 at 8:48 PM, anish singh <anish198519851985@gmail.com>wrote:
On Oct 3, 2013 8:28 PM, "sujan dutta" <stoned.seven@gmail.com> wrote:
Yes you can, infact network subsystem softirq are reactive so it can run
again.
however, reactivated softirq are not immediately process but until kernel handles the pending softirqs because it might introduce latency in user-space. And for better performance, when pending BH grows excessively then family of kernel threads are wakes up to handle the load. Family of threads mentioned here is called ksoftirqd. Linux uses the ksoftirqd as the general solution to schedule softirq's to run before next interrupt and by putting them under scheduler control. Also this prevents consecutive softirq's from monopolizing the CPU. This also has the effect that the priority of ksoftirq needs to be considered when running very CPU-intensive applications and networking to get the proper balance of softirq/user balance. Increasing ksoftirq priority to 0 (eventually more) is reported to cure problems with low network performance at high CPU load. I think softirq calling itself is a problem which is delicately managed by linux kernel developers and how to improve the code and logic is an active field where you can contribute.
On 27-Sep-2013, at 4:44 PM, Vishwas Srivastava (vishsriv) <
vishsriv@cisco.com> wrote:
Hi Group, I am a bit unclear if, I could schedule another BH while I am
already running in a BH ?
For example, if I am running in a SOFT IRQ, can I schedule a tasklet from there ??
Thanks, Vishwas S
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
participants (4)
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anish singh -
sujan dutta -
Vishwas Srivastava -
Vishwas Srivastava (vishsriv)