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[PATCH 2/4] large-fs: improve space diversification for ext4

To: xfs@xxxxxxxxxxx
Subject: [PATCH 2/4] large-fs: improve space diversification for ext4
From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Date: Tue, 9 Jul 2013 15:05:16 +0400
Cc: linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, dchinner@xxxxxxxxxx, Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1373367918-7516-1-git-send-email-dmonakhov@xxxxxxxxxx>
References: <1373367918-7516-1-git-send-email-dmonakhov@xxxxxxxxxx>
Currently we allocated several giant files one by one until limit,
so empty space is located as one chunk which limit code-path coverage.
This patch consume all space with NUM_SPACE_FILES files (by default 1024)
each has same size, and when truncate each one by required delta.
As result we have $NUM_SPACE_FILES chunks of free blocks distributed
across whole filesystem.
This should help us to avoid regressions similar to e7c9e3e99adf6c49

Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
 common/rc |   40 ++++++++++++++++------------------------
 1 files changed, 16 insertions(+), 24 deletions(-)

diff --git a/common/rc b/common/rc
index c44acea..902fc19 100644
--- a/common/rc
+++ b/common/rc
@@ -440,12 +440,17 @@ _setup_large_ext4_fs()
        fs_empty_space=$((50*1024*1024*1024))
 
        [ "$LARGE_SCRATCH_DEV" != yes ] && return 0
+       [ -z "$NUM_SPACE_FILES" ] && export NUM_SPACE_FILES=1024
        [ -z "$SCRATCH_DEV_EMPTY_SPACE" ] && SCRATCH_DEV_EMPTY_SPACE=0  
        fs_empty_space=$((fs_empty_space + $SCRATCH_DEV_EMPTY_SPACE))
        [ $fs_empty_space -ge $fs_size ] && return 0
 
        # calculate the size of the file we need to allocate.
+
        space_to_consume=$(($fs_size - $fs_empty_space))
+       file_size_falloc=$(($fs_size/$NUM_SPACE_FILES))
+       file_size_final=$(($space_to_consume/$NUM_SPACE_FILES))
+
        # mount the filesystem and create 16TB - 4KB files until we consume
        # all the necessary space.
        _scratch_mount 2>&1 >$tmp_dir/mnt.err
@@ -457,33 +462,20 @@ _setup_large_ext4_fs()
                return $status
        fi
        rm -f $tmp_dir/mnt.err
-
-       file_size=$((16*1024*1024*1024*1024 - 4096))
-       nfiles=0
-       while [ $space_to_consume -gt $file_size ]; do
-
+       mkdir $SCRATCH_MNT/.use_space
+       # Consume all space on filesytem
+       for ((nfiles = 0; nfiles < nfiles_total; nfiles++)); do 
                xfs_io -F -f \
-                       -c "truncate $file_size" \
-                       -c "falloc -k 0 $file_size" \
-                       $SCRATCH_MNT/.use_space.$nfiles 2>&1
-               status=$?
-               if [ $status -ne 0 ]; then
-                       break;
-               fi
-
-               space_to_consume=$(( $space_to_consume - $file_size ))
-               nfiles=$(($nfiles + 1))
+                       -c "truncate $file_size_falloc" \
+                       -c "falloc -k 0 $file_size_falloc" \
+                       $SCRATCH_MNT/.use_space/use_space.$nfiles 2>&1
        done
-
-       # consume the remaining space.
-       if [ $space_to_consume -gt 0 ]; then
+       # Truncate files to smaller size, will free chunks of space
+       for ((nfiles = 0; nfiles < nfiles_total; nfiles++)); do 
                xfs_io -F -f \
-                       -c "truncate $space_to_consume" \
-                       -c "falloc -k 0 $space_to_consume" \
-                       $SCRATCH_MNT/.use_space.$nfiles 2>&1
-               status=$?
-       fi
-       export NUM_SPACE_FILES=$nfiles
+                       -c "truncate $file_size_final" \
+                       $SCRATCH_MNT/.use_space/use_space.$nfiles 2>&1
+       done
 
        umount $SCRATCH_MNT
        if [ $status -ne 0 ]; then
-- 
1.7.1

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