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Tue, 01 Nov 2022 21:14:02 -0700 (PDT) Date: Wed, 2 Nov 2022 13:13:58 +0900 From: Sergey Senozhatsky To: Nhat Pham Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, minchan@kernel.org, ngupta@vflare.org, senozhatsky@chromium.org, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com Subject: Re: [PATCH v2 5/5] zsmalloc: Implement writeback mechanism for zsmalloc Message-ID: References: <202210272158.7swYwd23-lkp@intel.com> <20221027182736.513530-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221027182736.513530-1-nphamcs@gmail.com> ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=CMdN+Anc; spf=pass (imf23.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.170 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; 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spf=pass (imf23.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.170 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1667362444-349696 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (22/10/27 11:27), Nhat Pham wrote: > + > +static int zs_zpool_shrink(void *pool, unsigned int pages, > + unsigned int *reclaimed) > +{ > + unsigned int total = 0; > + int ret = -EINVAL; > + > + while (total < pages) { > + ret = zs_reclaim_page(pool, 8); > + if (ret < 0) > + break; > + total++; > + } > + > + if (reclaimed) > + *reclaimed = total; > + > + return ret; > +} The name collides with shrinker callbacks (compaction). That's a bit confusing, took me some time. > @@ -482,6 +504,7 @@ static struct zpool_driver zs_zpool_driver = { > .malloc_support_movable = true, > .malloc = zs_zpool_malloc, > .free = zs_zpool_free, > + .shrink = zs_zpool_shrink, > .map = zs_zpool_map, > .unmap = zs_zpool_unmap, > .total_size = zs_zpool_total_size, > @@ -955,6 +978,21 @@ static int trylock_zspage(struct zspage *zspage) > return 0; > } [..] > +#ifdef CONFIG_ZPOOL > +static int zs_reclaim_page(struct zs_pool *pool, unsigned int retries) > +{ > + int i, obj_idx, ret = 0; > + unsigned long handle; > + struct zspage *zspage; > + struct page *page; > + enum fullness_group fullness; > + > + /* Lock LRU and fullness list */ > + spin_lock(&pool->lock); > + if (!pool->ops || !pool->ops->evict || list_empty(&pool->lru) || You don't need pool->lock for pool->ops/pool->ops->evict checks. But, more importantly, I don't understand why is it even checked here? Why do we use ops->evict? Why cannot we call into zsmalloc evict directly? All of these are statically defined in zsmalloc, just don't provide .shrink if !define CONFIG_ZPOOL? Under what circumstances zsmalloc can provide .shrink but no ->evict?