Commit e5b46c75 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: speed up xfarray sort by sorting xfile page contents directly 



If all the records in an xfarray subset live within the same memory
page, we can short-circuit even more quicksort recursion by mapping that
page into the local CPU and using the kernel's heapsort function to sort
the subset.  On the author's computer, this reduces the runtime by
another 15% on a 500,000 element array.

Signed-off-by: default avatarDarrick J. Wong <djwong@kernel.org>
Reviewed-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
Reviewed-by: default avatarDave Chinner <dchinner@redhat.com>
parent 137db333

fs/xfs/scrub/trace.h

+20 −0
Original line number Diff line number Diff line
@@ -869,6 +869,26 @@ TRACE_EVENT(xfarray_isort, 
		  __entry->hi - __entry->lo)

);



TRACE_EVENT(xfarray_pagesort,

	TP_PROTO(struct xfarray_sortinfo *si, uint64_t lo, uint64_t hi),

	TP_ARGS(si, lo, hi),

	TP_STRUCT__entry(

		__field(unsigned long, ino)

		__field(unsigned long long, lo)

		__field(unsigned long long, hi)

	),

	TP_fast_assign(

		__entry->ino = file_inode(si->array->xfile->file)->i_ino;

		__entry->lo = lo;

		__entry->hi = hi;

	),

	TP_printk("xfino 0x%lx lo %llu hi %llu elts %llu",

		  __entry->ino,

		  __entry->lo,

		  __entry->hi,

		  __entry->hi - __entry->lo)

);



TRACE_EVENT(xfarray_qsort,

	TP_PROTO(struct xfarray_sortinfo *si, uint64_t lo, uint64_t hi),

	TP_ARGS(si, lo, hi),

fs/xfs/scrub/xfarray.c

+97 −0
Original line number Diff line number Diff line
@@ -545,6 +545,87 @@ xfarray_isort( 
	return xfile_obj_store(si->array->xfile, scratch, len, lo_pos);

}



/* Grab a page for sorting records. */

static inline int

xfarray_sort_get_page(

	struct xfarray_sortinfo	*si,

	loff_t			pos,

	uint64_t		len)

{

	int			error;



	error = xfile_get_page(si->array->xfile, pos, len, &si->xfpage);

	if (error)

		return error;



	/*

	 * xfile pages must never be mapped into userspace, so we skip the

	 * dcache flush when mapping the page.

	 */

	si->page_kaddr = kmap_local_page(si->xfpage.page);

	return 0;

}



/* Release a page we grabbed for sorting records. */

static inline int

xfarray_sort_put_page(

	struct xfarray_sortinfo	*si)

{

	if (!si->page_kaddr)

		return 0;



	kunmap_local(si->page_kaddr);

	si->page_kaddr = NULL;



	return xfile_put_page(si->array->xfile, &si->xfpage);

}



/* Decide if these records are eligible for in-page sorting. */

static inline bool

xfarray_want_pagesort(

	struct xfarray_sortinfo	*si,

	xfarray_idx_t		lo,

	xfarray_idx_t		hi)

{

	pgoff_t			lo_page;

	pgoff_t			hi_page;

	loff_t			end_pos;



	/* We can only map one page at a time. */

	lo_page = xfarray_pos(si->array, lo) >> PAGE_SHIFT;

	end_pos = xfarray_pos(si->array, hi) + si->array->obj_size - 1;

	hi_page = end_pos >> PAGE_SHIFT;



	return lo_page == hi_page;

}



/* Sort a bunch of records that all live in the same memory page. */

STATIC int

xfarray_pagesort(

	struct xfarray_sortinfo	*si,

	xfarray_idx_t		lo,

	xfarray_idx_t		hi)

{

	void			*startp;

	loff_t			lo_pos = xfarray_pos(si->array, lo);

	uint64_t		len = xfarray_pos(si->array, hi - lo);

	int			error = 0;



	trace_xfarray_pagesort(si, lo, hi);



	xfarray_sort_bump_loads(si);

	error = xfarray_sort_get_page(si, lo_pos, len);

	if (error)

		return error;



	xfarray_sort_bump_heapsorts(si);

	startp = si->page_kaddr + offset_in_page(lo_pos);

	sort(startp, hi - lo + 1, si->array->obj_size, si->cmp_fn, NULL);



	xfarray_sort_bump_stores(si);

	return xfarray_sort_put_page(si);

}



/* Return a pointer to the xfarray pivot record within the sortinfo struct. */

static inline void *xfarray_sortinfo_pivot(struct xfarray_sortinfo *si)

{
@@ -699,6 +780,10 @@ xfarray_qsort_push( 
 * 4. For small sets, load the records into the scratchpad and run heapsort on

 *    them because that is very fast.  In the author's experience, this yields

 *    a ~10% reduction in runtime.

 *

 *    If a small set is contained entirely within a single xfile memory page,

 *    map the page directly and run heap sort directly on the xfile page

 *    instead of using the load/store interface.  This halves the runtime.

 */



/*
@@ -744,6 +829,18 @@ xfarray_sort( 
			continue;

		}



		/*

		 * If directly mapping the page and sorting can solve our

		 * problems, we're done.

		 */

		if (xfarray_want_pagesort(si, lo, hi)) {

			error = xfarray_pagesort(si, lo, hi);

			if (error)

				goto out_free;

			si->stack_depth--;

			continue;

		}



		/* If insertion sort can solve our problems, we're done. */

		if (xfarray_want_isort(si, lo, hi)) {

			error = xfarray_isort(si, lo, hi);

fs/xfs/scrub/xfarray.h

+4 −0
Original line number Diff line number Diff line
@@ -80,6 +80,10 @@ struct xfarray_sortinfo { 
	/* XFARRAY_SORT_* flags; see below. */

	unsigned int		flags;



	/* Cache a page here for faster access. */

	struct xfile_page	xfpage;

	void			*page_kaddr;



#ifdef DEBUG

	/* Performance statistics. */

	uint64_t		loads;