Commit 351618b2 authored May 13, 2019 by Vitaly Wool Committed by Linus Torvalds May 14, 2019

mm/z3fold.c: improve compression by extending search

The current z3fold implementation only searches this CPU's page lists for
a fitting page to put a new object into.  This patch adds quick search for
very well fitting pages (i.  e.  those having exactly the required number
of free space) on other CPUs too, before allocating a new page for that
object.

Link: http://lkml.kernel.org/r/20190417103733.72ae81abe1552397c95a008e@gmail.com


Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 9050cce1

mm/z3fold.c

+36 −0

Original line number	Diff line number	Diff line
		@@ -522,6 +522,42 @@ lookup:
		}
		put_cpu_ptr(pool->unbuddied);

		if (!zhdr) {
		int cpu;

		/* look for _exact_ match on other cpus' lists */
		for_each_online_cpu(cpu) {
		struct list_head *l;

		unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
		spin_lock(&pool->lock);
		l = &unbuddied[chunks];

		zhdr = list_first_entry_or_null(READ_ONCE(l),
		struct z3fold_header, buddy);

		if (!zhdr \|\| !z3fold_page_trylock(zhdr)) {
		spin_unlock(&pool->lock);
		zhdr = NULL;
		continue;
		}
		list_del_init(&zhdr->buddy);
		zhdr->cpu = -1;
		spin_unlock(&pool->lock);

		page = virt_to_page(zhdr);
		if (test_bit(NEEDS_COMPACTING, &page->private)) {
		z3fold_page_unlock(zhdr);
		zhdr = NULL;
		if (can_sleep)
		cond_resched();
		continue;
		}
		kref_get(&zhdr->refcount);
		break;
		}
		}

		return zhdr;
		}

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