X-Git-Url: https://git.kernel.dk/?a=blobdiff_plain;f=HOWTO;h=ac9606988b2c73b510823bf445300fcb92a67222;hb=3ce3ad33ea92d9a4b032566249a3ad86dc3bd2a7;hp=3001fe74a0b6cffe19fba612e95c082580085c01;hpb=ae5888523480f094ce04375a45797e111273ab22;p=fio.git

diff --git a/HOWTO b/HOWTO
index 3001fe74..ac960698 100644
--- a/HOWTO
+++ b/HOWTO
@@ -1307,7 +1307,9 @@ write_bw_log=str If given, write a bandwidth log of the jobs in this job
 		jobs in their lifetime. The included fio_generate_plots
 		script uses gnuplot to turn these text files into nice
 		graphs. See write_lat_log for behaviour of given
-		filename. For this option, the suffix is _bw.log.
+		filename. For this option, the suffix is _bw.x.log, where
+		x is the index of the job (1..N, where N is the number of
+		jobs).
 
 write_lat_log=str Same as write_bw_log, except that this option stores io
 		submission, completion, and total latencies instead. If no
@@ -1317,14 +1319,16 @@ write_lat_log=str Same as write_bw_log, except that this option stores io
 
 		write_lat_log=foo
 
-		The actual log names will be foo_slat.log, foo_clat.log,
-		and foo_lat.log. This helps fio_generate_plot fine the logs
-		automatically.
+		The actual log names will be foo_slat.x.log, foo_clat.x.log,
+		and foo_lat.x.log, where x is the index of the job (1..N,
+		where N is the number of jobs). This helps fio_generate_plot
+		fine the logs automatically.
 
 write_iops_log=str Same as write_bw_log, but writes IOPS. If no filename is
 		given with this option, the default filename of
-		"jobname_type.log" is used. Even if the filename is given,
-		fio will still append the type of log.
+		"jobname_type.x.log" is used,where x is the index of the job
+		(1..N, where N is the number of jobs). Even if the filename
+		is given, fio will still append the type of log.
 
 log_avg_msec=int By default, fio will log an entry in the iops, latency,
 		or bw log for every IO that completes. When writing to the
@@ -1336,6 +1340,26 @@ log_avg_msec=int By default, fio will log an entry in the iops, latency,
 log_offset=int	If this is set, the iolog options will include the byte
 		offset for the IO entry as well as the other data values.
 
+log_compression=int	If this is set, fio will compress the IO logs as
+		it goes, to keep the memory footprint lower. When a log
+		reaches the specified size, that chunk is removed and
+		compressed in the background. Given that IO logs are
+		fairly highly compressible, this yields a nice memory
+		savings for longer runs. The downside is that the
+		compression will consume some background CPU cycles, so
+		it may impact the run. This, however, is also true if
+		the logging ends up consuming most of the system memory.
+		So pick your poison. The IO logs are saved normally at the
+		end of a run, by decompressing the chunks and storing them
+		in the specified log file. This feature depends on the
+		availability of zlib.
+
+log_store_compressed=bool	If set, and log_compression is also set,
+		fio will store the log files in a compressed format. They
+		can be decompressed with fio, using the --inflate-log
+		command line parameter. The files will be stored with a
+		.fz suffix.
+
 lockmem=int	Pin down the specified amount of memory with mlock(2). Can
 		potentially be used instead of removing memory or booting
 		with less memory to simulate a smaller amount of memory.