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Diffstat (limited to 'Documentation/vm/slub.txt')
| -rw-r--r-- | Documentation/vm/slub.txt | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index b0c6d1bbb434..699d8ea5c230 100644 --- a/Documentation/vm/slub.txt +++ b/Documentation/vm/slub.txt @@ -280,4 +280,63 @@ of other objects. slub_debug=FZ,dentry +Extended slabinfo mode and plotting +----------------------------------- + +The slabinfo tool has a special 'extended' ('-X') mode that includes: + - Slabcache Totals + - Slabs sorted by size (up to -N <num> slabs, default 1) + - Slabs sorted by loss (up to -N <num> slabs, default 1) + +Additionally, in this mode slabinfo does not dynamically scale sizes (G/M/K) +and reports everything in bytes (this functionality is also available to +other slabinfo modes via '-B' option) which makes reporting more precise and +accurate. Moreover, in some sense the `-X' mode also simplifies the analysis +of slabs' behaviour, because its output can be plotted using the +slabinfo-gnuplot.sh script. So it pushes the analysis from looking through +the numbers (tons of numbers) to something easier -- visual analysis. + +To generate plots: +a) collect slabinfo extended records, for example: + + while [ 1 ]; do slabinfo -X >> FOO_STATS; sleep 1; done + +b) pass stats file(-s) to slabinfo-gnuplot.sh script: + slabinfo-gnuplot.sh FOO_STATS [FOO_STATS2 .. FOO_STATSN] + +The slabinfo-gnuplot.sh script will pre-processes the collected records +and generates 3 png files (and 3 pre-processing cache files) per STATS +file: + - Slabcache Totals: FOO_STATS-totals.png + - Slabs sorted by size: FOO_STATS-slabs-by-size.png + - Slabs sorted by loss: FOO_STATS-slabs-by-loss.png + +Another use case, when slabinfo-gnuplot can be useful, is when you need +to compare slabs' behaviour "prior to" and "after" some code modification. +To help you out there, slabinfo-gnuplot.sh script can 'merge' the +`Slabcache Totals` sections from different measurements. To visually +compare N plots: + +a) Collect as many STATS1, STATS2, .. STATSN files as you need + while [ 1 ]; do slabinfo -X >> STATS<X>; sleep 1; done + +b) Pre-process those STATS files + slabinfo-gnuplot.sh STATS1 STATS2 .. STATSN + +c) Execute slabinfo-gnuplot.sh in '-t' mode, passing all of the +generated pre-processed *-totals + slabinfo-gnuplot.sh -t STATS1-totals STATS2-totals .. STATSN-totals + +This will produce a single plot (png file). + +Plots, expectedly, can be large so some fluctuations or small spikes +can go unnoticed. To deal with that, `slabinfo-gnuplot.sh' has two +options to 'zoom-in'/'zoom-out': + a) -s %d,%d overwrites the default image width and heigh + b) -r %d,%d specifies a range of samples to use (for example, + in `slabinfo -X >> FOO_STATS; sleep 1;' case, using + a "-r 40,60" range will plot only samples collected + between 40th and 60th seconds). + Christoph Lameter, May 30, 2007 +Sergey Senozhatsky, October 23, 2015 |