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Mon, 21 Nov 2022 22:37:34 -0800 (PST) Date: Tue, 22 Nov 2022 15:37:29 +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 v6 6/6] zsmalloc: Implement writeback mechanism for zsmalloc Message-ID: References: <20221119001536.2086599-1-nphamcs@gmail.com> <20221119001536.2086599-7-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221119001536.2086599-7-nphamcs@gmail.com> ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=X8lz3R6K; spf=pass (imf01.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.216.51 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; 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dmarc=pass (policy=none) header.from=chromium.org X-Stat-Signature: hgwrq87gf8oj4gq9bgfp8uha53mqhqt4 X-Rspamd-Queue-Id: 393AA4000D X-Rspamd-Server: rspam09 X-HE-Tag: 1669099055-125379 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 (22/11/18 16:15), Nhat Pham wrote: [..] > +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 (list_empty(&pool->lru)) { > + spin_unlock(&pool->lock); > + return -EINVAL; > + } > + > + for (i = 0; i < retries; i++) { > + struct size_class *class; > + > + zspage = list_last_entry(&pool->lru, struct zspage, lru); > + list_del(&zspage->lru); > + > + /* zs_free may free objects, but not the zspage and handles */ > + zspage->under_reclaim = true; > + > + class = zspage_class(pool, zspage); > + fullness = get_fullness_group(class, zspage); > + > + /* Lock out object allocations and object compaction */ > + remove_zspage(class, zspage, fullness); > + > + spin_unlock(&pool->lock); > + > + /* Lock backing pages into place */ > + lock_zspage(zspage); > + > + obj_idx = 0; > + page = zspage->first_page; > + while (1) { > + handle = find_alloced_obj(class, page, &obj_idx); > + if (!handle) { > + page = get_next_page(page); > + if (!page) > + break; > + obj_idx = 0; > + continue; > + } > + > + /* > + * This will write the object and call zs_free. > + * > + * zs_free will free the object, but the > + * under_reclaim flag prevents it from freeing > + * the zspage altogether. This is necessary so > + * that we can continue working with the > + * zspage potentially after the last object > + * has been freed. > + */ > + ret = pool->zpool_ops->evict(pool->zpool, handle); > + if (ret) > + goto next; > + > + obj_idx++; > + } > + > +next: > + /* For freeing the zspage, or putting it back in the pool and LRU list. */ > + spin_lock(&pool->lock); > + zspage->under_reclaim = false; > + > + if (!get_zspage_inuse(zspage)) { > + /* > + * Fullness went stale as zs_free() won't touch it > + * while the page is removed from the pool. Fix it > + * up for the check in __free_zspage(). > + */ > + zspage->fullness = ZS_EMPTY; > + > + __free_zspage(pool, class, zspage); > + spin_unlock(&pool->lock); > + return 0; > + } > + > + putback_zspage(class, zspage); > + list_add(&zspage->lru, &pool->lru); > + unlock_zspage(zspage); We probably better to cond_resched() somewhere here. Or in zs_zpool_shrink() loop. > + } > + > + spin_unlock(&pool->lock); > + return -EAGAIN; > +}