Difference between vruntime and sum_exec

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Operating Systems Linux Difference between vruntime and sum_exec_runtime Post 302815243 by kg_gaurav on Friday 31st of May 2013 10:05:59 AM

05-31-2013

Registered User

Difference between vruntime and sum_exec_runtime

While studying linux scheduler i looked into strct sched_entity and update_curr function which accounts for how much time a process have run.
The code says that vruntime is incremented by a weighted value(total run time weighted against number of process) while sum_exec_runtime is incremented by how much time passed since last accounting.
Here's link for function's defintion
update_curr :Linux/kernel/sched/fair.c - Linux Cross Reference - Free Electrons
__update_curr:Linux/kernel/sched/fair.c - Linux Cross Reference - Free Electrons

My question if we increment vruntime by weighted value how can we be sure that this is the time for which the process ran so far?
I think sum_exec_runtime gives exactly what we are looking for.
Please correct me if i'm wrong or any explanation for clearing this concept.

thanks

kg_gaurav

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LEARN ABOUT SUSE

elvtune

ELVTUNE(8)						      System Manager's Manual							ELVTUNE(8)

NAME

       elvtune - I/O elevator tuner

SYNOPSIS

       elvtune [-r r_lat] [-w w_lat] [-b b_max] device...
       elvtune -h
       elvtune -v

DESCRIPTION

       elvtune	allows	to  tune the I/O elevator per blockdevice queue basis. The tuning can be safely done at runtime. Tuning the elevator means
       being able to change disk performance and interactiveness. In the output of elvtune the address of the queue tuned will be shown and it can
       be  considered  as  a queue ID.	For example multiple partitions in the same harddisk will share the same queue and so tuning one partition
       will be like tuning the whole HD.

OPTIONS

       -r r_lat
	      set the max latency that the I/O scheduler will provide on each read.

       -w w_lat
	      set the max latency that the I/O scheduler will provide on each write.

       -b b_max
	      max coalescing factor allowed on writes when there are reads pending in the queue.

       -h     help.

       -v     version.

NOTE

       Actually the only fields tunable are those relative to the IO scheduler. It's not possible to select a one-way or two-way elevator yet.

       For logical blockdevices like LVM the tuning has to be done on the physical devices. Tuning the queue of the LVM logical device is useless.

RETURN VALUE

       0 on success and 1 on failure.

HISTORY

       Ioctls for tuning elevator behaviour were added in Linux 2.3.99-pre1.

AUTHORS

       Andrea Arcangeli <andrea@suse.de> SuSE

AVAILABILITY

       The elvtune command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

Version 1.0							   14 March 2000							ELVTUNE(8)

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