b2c77a57e4
Typical cputime stats infrastructure relies on the timer tick and its periodic polling on the CPU to account the amount of time spent by the CPUs and the tasks per high level domains such as userspace, kernelspace, guest, ... Now we are preparing to implement full dynticks capability on Linux for Real Time and HPC users who want full CPU isolation. This feature requires a cputime accounting that doesn't depend on the timer tick. To implement it, this new cputime infrastructure plugs into kernel/user/guest boundaries to take snapshots of cputime and flush these to the stats when needed. This performs pretty much like CONFIG_VIRT_CPU_ACCOUNTING except that context location and cputime snaphots are synchronized between write and read side such that the latter can safely retrieve the pending tickless cputime of a task and add it to its latest cputime snapshot to return the correct result to the user. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAABAgAGBQJRBsKnAAoJEIUkVEdQjox3lMgP/2R6DU2f8PyGIao3hne4M3Pu L3q+mAG53b24Dy014KeW7gd8yv45fE7wp/rs8CGLte9VzbLkRCDSFQPgBuXVagRj tV5nfAuqD0wHTnA+HhBE3l3C2RKAPGIu79rBpnIR/QIPPl8Z3Dby8YgmxEQKDf8G j7MEBu2LthSuqEi2ZXemnO5r0oEnQAzAp4TTi/M38k0Fmt59nOGyjLnI+xHYCBMa 1pnz7j3jjR9NJExGu8iVvbo+jupuQngP8qmkLXHvYnj/TEJNwzO1hHVoSwOpjYpS 9ycl+T8IKQLbAkBywLtq3Mzde43xt/t8wYyGZ0oAV+Z7MIpz/9YIfDJwqQeqoNbD dAdbNjKMbsxCgmrnyqSagfMQg/r3CPZ4vf40TMCaN4gNUJC4Ie+E4kPRKRh59+PB Ukthmqujn0f40LAa+HXTUuzafd3b0s/ewH+8FuQ6LAG9b5+WnoN8JTJ5u6+ydokO ZleeOowuRZZEg+abQ8Sm2GRm/BzN29gi/npb//I+ZDXWv/+3yccgsiPjCRzCAAaO g1RmYryFSRUwHQbGNNypVWVuOLWvrBQ4jqbGO7BBuBByZMSHryKxR6mb+inH3qLE xIDM9SdSJisc292OzoFKwVZki4MaXaadJXJduVvqYlZQvXXs7eAa4wo3euhtVITD NLQO5OZXE4oIQmDFb0FV =1Tzp -----END PGP SIGNATURE----- Merge tag 'full-dynticks-cputime-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into sched/core Pull full-dynticks (user-space execution is undisturbed and receives no timer IRQs) preparation changes that convert the cputime accounting code to be full-dynticks ready, from Frederic Weisbecker: "This implements the cputime accounting on full dynticks CPUs. Typical cputime stats infrastructure relies on the timer tick and its periodic polling on the CPU to account the amount of time spent by the CPUs and the tasks per high level domains such as userspace, kernelspace, guest, ... Now we are preparing to implement full dynticks capability on Linux for Real Time and HPC users who want full CPU isolation. This feature requires a cputime accounting that doesn't depend on the timer tick. To implement it, this new cputime infrastructure plugs into kernel/user/guest boundaries to take snapshots of cputime and flush these to the stats when needed. This performs pretty much like CONFIG_VIRT_CPU_ACCOUNTING except that context location and cputime snaphots are synchronized between write and read side such that the latter can safely retrieve the pending tickless cputime of a task and add it to its latest cputime snapshot to return the correct result to the user." Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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