Re: [PATCH] concurrent block allocation for ext3

[Alex Tomas]

>>>>> Andreas Dilger (AD) writes:

 AD> Any ideas on how much this improves the performance?  What sort
 AD> of tests were you running?  We could improve things a bit further
 AD> by having separate per-group locks for the update of the group
 AD> descriptor info, and only lazily update the superblock at statfs
 AD> and unmount time (with a suitable feature flag so e2fsck can fix
 AD> this up at recovery time), but you seem to have gotten the
 AD> majority of the parallelism from this fix.

I'm trying to measure improvement.

The tests were:

1) on big fs (1GB)
lots of processes (up to 50) creating, removing directories and files +
untaring kernel and make -j4 bzImage +
dd if=/dev/zero of=/mnt/dump.file bs=1M count=8000; rm -f /mnt/dump.file

2) on small fs (64MB)
20 processes create and remove lots of files and directories

in fact, I catched dozens of debug messages about set_bit collision. Then
I fscked fs to be sure all is ok.

 >> @@ -214,11 +213,13 @@ block + i); BUFFER_TRACE(bitmap_bh, "bit
 >> already cleared"); } else { +
 >> spin_lock(&EXT3_SB(sb)->s_alloc_lock); dquot_freed_blocks++;
 gdp-> bg_free_blocks_count =
 >> cpu_to_le16(le16_to_cpu(gdp->bg_free_blocks_count)+1);
 es-> s_free_blocks_count =
 >> cpu_to_le32(le32_to_cpu(es->s_free_blocks_count)+1); +
 >> spin_unlock(&EXT3_SB(sb)->s_alloc_lock);

 AD> One minor nit is that you left an ext3_error() for the "bit
 AD> already cleared" case just above this patch hunk.

hmm. whats wrong with it?

with best regards, Alex