From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753990AbcKAVDu (ORCPT ); Tue, 1 Nov 2016 17:03:50 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33553 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752158AbcKAVDt (ORCPT ); Tue, 1 Nov 2016 17:03:49 -0400 MIME-Version: 1.0 In-Reply-To: References: <20161027130647.782b8ab1f71555200ba15605@gmail.com> <20161027130803.82fa7db8f649b5977190208b@gmail.com> From: Vitaly Wool Date: Tue, 1 Nov 2016 22:03:46 +0100 Message-ID: Subject: Re: [PATCHv3 1/3] z3fold: make counters atomic To: Dan Streetman Cc: Linux-MM , linux-kernel , Andrew Morton Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 1, 2016 at 9:03 PM, Dan Streetman wrote: > On Thu, Oct 27, 2016 at 7:08 AM, Vitaly Wool wrote: >> This patch converts pages_nr per-pool counter to atomic64_t. >> It also introduces a new counter, unbuddied_nr, which is >> atomic64_t, too, to track the number of unbuddied (compactable) >> z3fold pages. > > so, with the use of workqueues, do we still need the unbuddied_nr > counter? It doesn't seem to be used in later patches? I'm going to add sysfs/debugfs accounting a bit later so it won't rest unused. Also, with a per-page lock (if I come up with something reasonable) it could be still worth going back to shrinker. > changing the pages_nr to atomic is a good idea though, so we can > safely read it without needing the pool lock. > >> >> Signed-off-by: Vitaly Wool >> --- >> mm/z3fold.c | 33 +++++++++++++++++++++++++-------- >> 1 file changed, 25 insertions(+), 8 deletions(-) >> >> diff --git a/mm/z3fold.c b/mm/z3fold.c >> index 8f9e89c..5ac325a 100644 >> --- a/mm/z3fold.c >> +++ b/mm/z3fold.c >> @@ -69,6 +69,7 @@ struct z3fold_ops { >> * @lru: list tracking the z3fold pages in LRU order by most recently >> * added buddy. >> * @pages_nr: number of z3fold pages in the pool. >> + * @unbuddied_nr: number of unbuddied z3fold pages in the pool. >> * @ops: pointer to a structure of user defined operations specified at >> * pool creation time. >> * >> @@ -80,7 +81,8 @@ struct z3fold_pool { >> struct list_head unbuddied[NCHUNKS]; >> struct list_head buddied; >> struct list_head lru; >> - u64 pages_nr; >> + atomic64_t pages_nr; >> + atomic64_t unbuddied_nr; >> const struct z3fold_ops *ops; >> struct zpool *zpool; >> const struct zpool_ops *zpool_ops; >> @@ -234,7 +236,8 @@ static struct z3fold_pool *z3fold_create_pool(gfp_t gfp, >> INIT_LIST_HEAD(&pool->unbuddied[i]); >> INIT_LIST_HEAD(&pool->buddied); >> INIT_LIST_HEAD(&pool->lru); >> - pool->pages_nr = 0; >> + atomic64_set(&pool->pages_nr, 0); >> + atomic64_set(&pool->unbuddied_nr, 0); >> pool->ops = ops; >> return pool; >> } >> @@ -334,6 +337,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, >> continue; >> } >> list_del(&zhdr->buddy); >> + atomic64_dec(&pool->unbuddied_nr); >> goto found; >> } >> } >> @@ -346,7 +350,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, >> if (!page) >> return -ENOMEM; >> spin_lock(&pool->lock); >> - pool->pages_nr++; >> + atomic64_inc(&pool->pages_nr); >> zhdr = init_z3fold_page(page); >> >> if (bud == HEADLESS) { >> @@ -369,6 +373,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp, >> /* Add to unbuddied list */ >> freechunks = num_free_chunks(zhdr); >> list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); >> + atomic64_inc(&pool->unbuddied_nr); >> } else { >> /* Add to buddied list */ >> list_add(&zhdr->buddy, &pool->buddied); >> @@ -412,6 +417,10 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) >> /* HEADLESS page stored */ >> bud = HEADLESS; >> } else { >> + bool is_unbuddied = zhdr->first_chunks == 0 || >> + zhdr->middle_chunks == 0 || >> + zhdr->last_chunks == 0; >> + >> bud = handle_to_buddy(handle); >> >> switch (bud) { >> @@ -431,6 +440,8 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) >> spin_unlock(&pool->lock); >> return; >> } >> + if (is_unbuddied) >> + atomic64_dec(&pool->unbuddied_nr); >> } >> >> if (test_bit(UNDER_RECLAIM, &page->private)) { >> @@ -451,12 +462,13 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle) >> list_del(&page->lru); >> clear_bit(PAGE_HEADLESS, &page->private); >> free_z3fold_page(zhdr); >> - pool->pages_nr--; >> + atomic64_dec(&pool->pages_nr); >> } else { >> z3fold_compact_page(zhdr); >> /* Add to the unbuddied list */ >> freechunks = num_free_chunks(zhdr); >> list_add(&zhdr->buddy, &pool->unbuddied[freechunks]); >> + atomic64_inc(&pool->unbuddied_nr); >> } >> >> spin_unlock(&pool->lock); >> @@ -520,6 +532,11 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) >> zhdr = page_address(page); >> if (!test_bit(PAGE_HEADLESS, &page->private)) { >> list_del(&zhdr->buddy); >> + if (zhdr->first_chunks == 0 || >> + zhdr->middle_chunks == 0 || >> + zhdr->last_chunks == 0) >> + atomic64_dec(&pool->unbuddied_nr); >> + >> /* >> * We need encode the handles before unlocking, since >> * we can race with free that will set >> @@ -569,7 +586,7 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) >> */ >> clear_bit(PAGE_HEADLESS, &page->private); >> free_z3fold_page(zhdr); >> - pool->pages_nr--; >> + atomic64_dec(&pool->pages_nr); >> spin_unlock(&pool->lock); >> return 0; >> } else if (!test_bit(PAGE_HEADLESS, &page->private)) { >> @@ -584,6 +601,7 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries) >> freechunks = num_free_chunks(zhdr); >> list_add(&zhdr->buddy, >> &pool->unbuddied[freechunks]); >> + atomic64_inc(&pool->unbuddied_nr); >> } >> } >> >> @@ -672,12 +690,11 @@ static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle) >> * z3fold_get_pool_size() - gets the z3fold pool size in pages >> * @pool: pool whose size is being queried >> * >> - * Returns: size in pages of the given pool. The pool lock need not be >> - * taken to access pages_nr. >> + * Returns: size in pages of the given pool. >> */ >> static u64 z3fold_get_pool_size(struct z3fold_pool *pool) >> { >> - return pool->pages_nr; >> + return atomic64_read(&pool->pages_nr); >> } >> >> /***************** >> -- >> 2.4.2