lkml.org 
[lkml]   [1999]   [Jun]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectNew semaphore __wake_up() implementation ...

Hi guys,

I've modified the "up" routine coded in file sched.c to get
more speed and, IMVHO more correctness.
Previous code in __wake_up() release all task that ( except one )
goes immediatly scheduled.
Given:

N = Number of tasks in runqueue
M = Number of tasks in semaphore queue
L = The cost of linear scan of wait queue of semaphore
W = The cost of a wakeup() operation
S = The cost of a schedule() search of next to run

the total cost of a "up" operation is:

TCo = L + M * W + (M - 1) * S

My new implementation release only the best suitable process to run,
resulting in a cost:

TCn = L + W

The new code linear scan the semaphore queue list and pick the best
task to wakeup ( in a goodness sense ).
If the process counters is exhausted ( it happens very rarely ) I've 2
way to follow:
1) Do a recalculate loop inside __wake_up()
2) Leave this case to fall into the previous implementation and releasing all tasks

I choose 2 to leave process counter recharging inside the schedule() function.

Tomorrow I'll post to linux-kernel my patch as long as a test program and
speed results.

Cheers,
Davide.

--
"Debian, the Freedom in Freedom."




-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:52    [W:0.128 / U:0.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site