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libjio/doc/guide.rst  view on Meta::CPAN

All other operations (committing a transaction, rolling it back, adding
operations, etc.) and all the wrappers are safe and don't require any special
considerations.


Lingering transactions
----------------------

If you need to increase performance, you can use lingering transactions. In
this mode, transactions take up more disk space but allows you to do the
synchronous write only once, making commits much faster. To use them, just add
*J_LINGER* to the *jflags* parameter in *jopen()*. You should call *jsync()*
frequently to avoid using up too much space, or start an asynchronous thread
that calls *jsync()* automatically using *jfs_autosync_start()*. Note that
files opened with this mode must not be opened by more than one process at the
same time.


Disk layout
-----------

The library creates a single directory for each file opened, named after it.
So if we open a file *output*, a directory named *.output.jio* will be

libjio/libjio/trans.c  view on Meta::CPAN

	off_t lr, min_offset;
	struct operation *op, *start_op;

	if (ts->flags & J_NOLOCK)
		return 0;

	/* Lock/unlock always in the same order to avoid deadlocks. We will
	 * begin with the operation that has the smallest start offset, and go
	 * from there.
	 * Note that this is O(n^2), but n is usually (very) small, and we're
	 * about to do synchronous I/O, so it's not really worrying. It has a
	 * small optimization to help when the operations tend to be in the
	 * right order. */
	nops = 0;
	min_offset = 0;
	start_op = ts->op;
	while (nops < ts->numops_r + ts->numops_w) {
		for (op = start_op; op != NULL; op = op->next) {
			if (min_offset < op->offset)
				continue;
			min_offset = op->offset;