path: root/Documentation/accounting/delay-accounting.txt
diff options
authorShailabh Nagar <nagar@watson.ibm.com>2006-07-14 00:24:44 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-07-14 21:53:57 -0700
commitad4ecbcba72855a2b5319b96e2a3a65ed1ca3bfd (patch)
treea2f5b98598948525de77ab594e4432f09a230388 /Documentation/accounting/delay-accounting.txt
parent25890454667b3295f67b3372352be90705f8667c (diff)
[PATCH] delay accounting taskstats interface send tgid once
Send per-tgid data only once during exit of a thread group instead of once with each member thread exit. Currently, when a thread exits, besides its per-tid data, the per-tgid data of its thread group is also sent out, if its thread group is non-empty. The per-tgid data sent consists of the sum of per-tid stats for all *remaining* threads of the thread group. This patch modifies this sending in two ways: - the per-tgid data is sent only when the last thread of a thread group exits. This cuts down heavily on the overhead of sending/receiving per-tgid data, especially when other exploiters of the taskstats interface aren't interested in per-tgid stats - the semantics of the per-tgid data sent are changed. Instead of being the sum of per-tid data for remaining threads, the value now sent is the true total accumalated statistics for all threads that are/were part of the thread group. The patch also addresses a minor issue where failure of one accounting subsystem to fill in the taskstats structure was causing the send of taskstats to not be sent at all. The patch has been tested for stability and run cerberus for over 4 hours on an SMP. [akpm@osdl.org: bugfixes] Signed-off-by: Shailabh Nagar <nagar@watson.ibm.com> Signed-off-by: Balbir Singh <balbir@in.ibm.com> Cc: Jay Lan <jlan@engr.sgi.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'Documentation/accounting/delay-accounting.txt')
1 files changed, 4 insertions, 9 deletions
diff --git a/Documentation/accounting/delay-accounting.txt b/Documentation/accounting/delay-accounting.txt
index f3dc0ca04fa..be215e58423 100644
--- a/Documentation/accounting/delay-accounting.txt
+++ b/Documentation/accounting/delay-accounting.txt
@@ -48,9 +48,10 @@ counter (say cpu_delay_total) for a task will give the delay
experienced by the task waiting for the corresponding resource
in that interval.
-When a task exits, records containing the per-task and per-process statistics
-are sent to userspace without requiring a command. More details are given in
-the taskstats interface description.
+When a task exits, records containing the per-task statistics
+are sent to userspace without requiring a command. If it is the last exiting
+task of a thread group, the per-tgid statistics are also sent. More details
+are given in the taskstats interface description.
The getdelays.c userspace utility in this directory allows simple commands to
be run and the corresponding delay statistics to be displayed. It also serves
@@ -107,9 +108,3 @@ IO count delay total
0 0
MEM count delay total
0 0