X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=HOWTO;h=fbe8f7919988db293b921334268a424e887604fd;hp=d5fa98768735302bdfed61012744b8cd8ff7eca7;hb=43f09da1e2c0fa04707e2bda4a361118091532c6;hpb=30a4588ac62017cf6ff9a64a4d18118251d8713f

diff --git a/HOWTO b/HOWTO
index d5fa9876..fbe8f791 100644
--- a/HOWTO
+++ b/HOWTO
@@ -9,6 +9,7 @@ Table of contents
 6. Normal output
 7. Terse output
 8. Trace file format
+9. CPU idleness profiling
 
 1.0 Overview and history
 ------------------------
@@ -353,6 +354,12 @@ kb_base=int	The base unit for a kilobyte. The defacto base is 2^10, 1024.
 		ten unit instead, for obvious reasons. Allow values are
 		1024 or 1000, with 1024 being the default.
 
+unified_rw_reporting=bool	Fio normally reports statistics on a per
+		data direction basis, meaning that read, write, and trim are
+		accounted and reported separately. If this option is set,
+		the fio will sum the results and report them as "mixed"
+		instead.
+
 randrepeat=bool	For random IO workloads, seed the generator in a predictable
 		way so that results are repeatable across repetitions.
 
@@ -769,7 +776,7 @@ random_generator=str	Fio supports the following engines for generating
 		block sizes, not with workloads that use multiple block
 		sizes. If used with such a workload, fio may read or write
 		some blocks multiple times.
-		
+
 nice=int	Run the job with the given nice value. See man nice(2).
 
 prio=int	Set the io priority value of this job. Linux limits us to
@@ -1396,6 +1403,9 @@ that defines them is selected.
 [netsplice] port=int
 [net] port=int	The TCP or UDP port to bind to or connect to.
 
+[netsplice] nodelay=bool
+[net] nodelay=bool	Set TCP_NODELAY on TCP connections.
+
 [netsplice] protocol=str
 [netsplice] proto=str
 [net] protocol=str
@@ -1687,3 +1697,18 @@ write      Write 'length' bytes beginning from 'offset'
 sync       fsync() the file
 datasync   fdatasync() the file
 trim       trim the given file from the given 'offset' for 'length' bytes
+
+
+9.0 CPU idleness profiling
+
+In some cases, we want to understand CPU overhead in a test. For example,
+we test patches for the specific goodness of whether they reduce CPU usage.
+fio implements a balloon approach to create a thread per CPU that runs at
+idle priority, meaning that it only runs when nobody else needs the cpu.
+By measuring the amount of work completed by the thread, idleness of each
+CPU can be derived accordingly.
+
+An unit work is defined as touching a full page of unsigned characters. Mean
+and standard deviation of time to complete an unit work is reported in "unit
+work" section. Options can be chosen to report detailed percpu idleness or
+overall system idleness by aggregating percpu stats.