From 08bdeb50f763aa3cb8b910a4cff3b14f17f076a6 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Tue, 31 Oct 2017 10:18:54 -0600 Subject: [PATCH] Update compression documentation Make it clearer (hopefully) that buffer_compress_chunk should be used if the user wants a finer granularity than the write block size. Signed-off-by: Jens Axboe --- HOWTO | 7 ++++--- fio.1 | 7 ++++--- 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/HOWTO b/HOWTO index f151350c..e510e18c 100644 --- a/HOWTO +++ b/HOWTO @@ -1453,8 +1453,8 @@ Buffers and memory mix of random data and a fixed pattern. The fixed pattern is either zeros, or the pattern specified by :option:`buffer_pattern`. If the pattern option is used, it might skew the compression ratio slightly. Note that this is per - block size unit, for file/disk wide compression level that matches this - setting, you'll also want to set :option:`refill_buffers`. + block size unit, see :option:`buffer_compress_chunk` for setting a finer + granularity of compression regions. .. option:: buffer_compress_chunk=int @@ -1463,7 +1463,8 @@ Buffers and memory will provide :option:`buffer_compress_percentage` of blocksize random data, followed by the remaining zeroed. With this set to some chunk size smaller than the block size, fio can alternate random and zeroed data throughout the - I/O buffer. + I/O buffer. This is particularly useful when bigger block sizes are used + for a job. .. option:: buffer_pattern=str diff --git a/fio.1 b/fio.1 index 198b9d85..8e983724 100644 --- a/fio.1 +++ b/fio.1 @@ -1242,8 +1242,8 @@ WRITEs) that compresses to the specified level. Fio does this by providing a mix of random data and a fixed pattern. The fixed pattern is either zeros, or the pattern specified by \fBbuffer_pattern\fR. If the pattern option is used, it might skew the compression ratio slightly. Note that this is per -block size unit, for file/disk wide compression level that matches this -setting, you'll also want to set \fBrefill_buffers\fR. +block size unit, see \fBbuffer_compress_chunk\fR for setting a finer granularity +of compressible regions. .TP .BI buffer_compress_chunk \fR=\fPint See \fBbuffer_compress_percentage\fR. This setting allows fio to manage @@ -1251,7 +1251,8 @@ how big the ranges of random data and zeroed data is. Without this set, fio will provide \fBbuffer_compress_percentage\fR of blocksize random data, followed by the remaining zeroed. With this set to some chunk size smaller than the block size, fio can alternate random and zeroed data throughout the -I/O buffer. +I/O buffer. This is particularly useful when bigger block sizes are used +for a job. .TP .BI buffer_pattern \fR=\fPstr If set, fio will fill the I/O buffers with this pattern or with the contents -- 2.25.1