[Ocfs2-devel] [PATCH v2] ocfs2: improve recovery performance

[Gang He]

Hello Junxiao,

I think this change will bring a performance improvement, but from the function comments
/*
 * JBD Might read a cached version of another nodes journal file. We
 * don't want this as this file changes often and we get no
 * notification on those changes. The only way to be sure that we've
 * got the most up to date version of those blocks then is to force
 * read them off disk. Just searching through the buffer cache won't
 * work as there may be pages backing this file which are still marked
 * up to date. We know things can't change on this file underneath us
 * as we have the lock by now :)
 */
static int ocfs2_force_read_journal(struct inode *inode)

Did we consider this potential risk behind this patch? I am not familiar with this part code, 
I want to know if there is any sync mechanism to make sure the block cache for another node journal file is really the latest data?  



Thanks
Gang 


>>> 
> On 2016/6/17 17:28, Junxiao Bi wrote:
>> Journal replay will be run when do recovery for a dead node,
>> to avoid the stale cache impact, all blocks of dead node's
>> journal inode were reload from disk. This hurts the performance,
>> check whether one block is cached before reload it can improve
>> a lot performance. In my test env, the time doing recovery was
>> improved from 120s to 1s.
>> 
>> Signed-off-by: Junxiao Bi <junxiao.bi at oracle.com>
> Looks good to me. And it indeed has performance improvement from my
> test.
> Reviewed-by: Joseph Qi <joseph.qi at huawei.com>
> 
>> ---
>>  fs/ocfs2/journal.c |   41 ++++++++++++++++++++++-------------------
>>  1 file changed, 22 insertions(+), 19 deletions(-)
>> 
>> diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
>> index e607419cdfa4..bc0e21e8a674 100644
>> --- a/fs/ocfs2/journal.c
>> +++ b/fs/ocfs2/journal.c
>> @@ -1159,10 +1159,8 @@ static int ocfs2_force_read_journal(struct inode 
> *inode)
>>  	int status = 0;
>>  	int i;
>>  	u64 v_blkno, p_blkno, p_blocks, num_blocks;
>> -#define CONCURRENT_JOURNAL_FILL 32ULL
>> -	struct buffer_head *bhs[CONCURRENT_JOURNAL_FILL];
>> -
>> -	memset(bhs, 0, sizeof(struct buffer_head *) * CONCURRENT_JOURNAL_FILL);
>> +	struct buffer_head *bh = NULL;
>> +	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
>>  
>>  	num_blocks = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
>>  	v_blkno = 0;
>> @@ -1174,29 +1172,34 @@ static int ocfs2_force_read_journal(struct inode 
> *inode)
>>  			goto bail;
>>  		}
>>  
>> -		if (p_blocks > CONCURRENT_JOURNAL_FILL)
>> -			p_blocks = CONCURRENT_JOURNAL_FILL;
>> +		for (i = 0; i < p_blocks; i++) {
>> +			bh = __find_get_block(osb->sb->s_bdev, p_blkno,
>> +					osb->sb->s_blocksize);
>> +			/* block not cached. */
>> +			if (!bh) {
>> +				p_blkno++;
>> +				continue;
>> +			}
>>  
>> -		/* We are reading journal data which should not
>> -		 * be put in the uptodate cache */
>> -		status = ocfs2_read_blocks_sync(OCFS2_SB(inode->i_sb),
>> -						p_blkno, p_blocks, bhs);
>> -		if (status < 0) {
>> -			mlog_errno(status);
>> -			goto bail;
>> -		}
>> +			brelse(bh);
>> +			bh = NULL;
>> +			/* We are reading journal data which should not
>> +			 * be put in the uptodate cache.
>> +			 */
>> +			status = ocfs2_read_blocks_sync(osb, p_blkno, 1, &bh);
>> +			if (status < 0) {
>> +				mlog_errno(status);
>> +				goto bail;
>> +			}
>>  
>> -		for(i = 0; i < p_blocks; i++) {
>> -			brelse(bhs[i]);
>> -			bhs[i] = NULL;
>> +			brelse(bh);
>> +			bh = NULL;
>>  		}
>>  
>>  		v_blkno += p_blocks;
>>  	}
>>  
>>  bail:
>> -	for(i = 0; i < CONCURRENT_JOURNAL_FILL; i++)
>> -		brelse(bhs[i]);
>>  	return status;
>>  }
>>  
>> 
> 
> 
> 
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