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Re: when does journal flush with data=journal



On Feb 08, 2002  12:59 -0800, Andrew Morton wrote:
> In Bill's testing, commits will most likely be forced by exhaustion
> of journal space, rather than kjournald timeout.  This is determined
> by journal->j_max_transaction_buffers, which is initialised in journal_reset():
> 
>         journal->j_max_transaction_buffers = journal->j_maxlen / 4;
> 
> probably this could be changed to journal->j_maxlen / 2 with no
> ill effect.  I haven't tried it.

At one time I recall Stephen saying that it might be limited to
j_maxlen / 3, but I could be wrong.

> The other (complimentary) option is to simply hack mke2fs so that it permits
> larger journals.  In e2fsprogs's misc/util.c:figure_journal_size():
> 
> -                if (j_blocks < 1024 || j_blocks > 102400) {
> +                if (j_blocks < 1024 || j_blocks >= fs->super->s_free_blocks_count) {

Probably better to limit it to j_blocks >= fs->super->s_free_blocks_count / 2
so that you have enough filesystem space to be able to write out the data
from the journal.

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/





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