From patchwork Fri Feb 26 01:18:31 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 388430 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24E32C433E9 for ; Fri, 26 Feb 2021 01:19:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D31A064EFA for ; Fri, 26 Feb 2021 01:19:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229556AbhBZBTD (ORCPT ); Thu, 25 Feb 2021 20:19:03 -0500 Received: from mail.kernel.org ([198.145.29.99]:50196 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229953AbhBZBSs (ORCPT ); Thu, 25 Feb 2021 20:18:48 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id E654C64EFA; Fri, 26 Feb 2021 01:18:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614302312; bh=7fPrW9lQi6WK+ERSMk9fOQf7ZFDZTTfqz+iYdejlxho=; h=Date:From:To:Subject:In-Reply-To:From; b=A0BZz2wDuEeM5CEvfQBLzkah/CVKyS8gxZUlvPLYXtBfNOy1A4RWPGpPZO1jLDoOV rJOyDPMqJAdvG24ruIPylOJhWqwn3VGgdGmGXC63xk5GP14AY4dz1dqZjOwCIo2OPJ ez8WxAJQwyE8P0QSicY+x1CSBcqxA6tk3FWN9DBI= Date: Thu, 25 Feb 2021 17:18:31 -0800 From: Andrew Morton To: akpm@linux-foundation.org, linux-mm@kvack.org, minchan@kernel.org, mm-commits@vger.kernel.org, sergey.senozhatsky@gmail.com, stable@vger.kernel.org, torvalds@linux-foundation.org, wu-yan@tcl.com Subject: [patch 050/118] zsmalloc: account the number of compacted pages correctly Message-ID: <20210226011831.CV7rry-jF%akpm@linux-foundation.org> In-Reply-To: <20210225171452.713967e96554bb6a53e44a19@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Rokudo Yan Subject: zsmalloc: account the number of compacted pages correctly There exists multiple path may do zram compaction concurrently. 1. auto-compaction triggered during memory reclaim 2. userspace utils write zram/compaction node So, multiple threads may call zs_shrinker_scan/zs_compact concurrently. But pages_compacted is a per zsmalloc pool variable and modification of the variable is not serialized(through under class->lock). There are two issues here: 1. the pages_compacted may not equal to total number of pages freed(due to concurrently add). 2. zs_shrinker_scan may not return the correct number of pages freed(issued by current shrinker). The fix is simple: 1. account the number of pages freed in zs_compact locally. 2. use actomic variable pages_compacted to accumulate total number. Link: https://lkml.kernel.org/r/20210202122235.26885-1-wu-yan@tcl.com Fixes: 860c707dca155a56 ("zsmalloc: account the number of compacted pages") Signed-off-by: Rokudo Yan Cc: Minchan Kim Cc: Sergey Senozhatsky Cc: Signed-off-by: Andrew Morton --- drivers/block/zram/zram_drv.c | 2 +- include/linux/zsmalloc.h | 2 +- mm/zsmalloc.c | 17 +++++++++++------ 3 files changed, 13 insertions(+), 8 deletions(-) --- a/drivers/block/zram/zram_drv.c~zsmalloc-account-the-number-of-compacted-pages-correctly +++ a/drivers/block/zram/zram_drv.c @@ -1081,7 +1081,7 @@ static ssize_t mm_stat_show(struct devic zram->limit_pages << PAGE_SHIFT, max_used << PAGE_SHIFT, (u64)atomic64_read(&zram->stats.same_pages), - pool_stats.pages_compacted, + atomic_long_read(&pool_stats.pages_compacted), (u64)atomic64_read(&zram->stats.huge_pages), (u64)atomic64_read(&zram->stats.huge_pages_since)); up_read(&zram->init_lock); --- a/include/linux/zsmalloc.h~zsmalloc-account-the-number-of-compacted-pages-correctly +++ a/include/linux/zsmalloc.h @@ -35,7 +35,7 @@ enum zs_mapmode { struct zs_pool_stats { /* How many pages were migrated (freed) */ - unsigned long pages_compacted; + atomic_long_t pages_compacted; }; struct zs_pool; --- a/mm/zsmalloc.c~zsmalloc-account-the-number-of-compacted-pages-correctly +++ a/mm/zsmalloc.c @@ -2212,11 +2212,13 @@ static unsigned long zs_can_compact(stru return obj_wasted * class->pages_per_zspage; } -static void __zs_compact(struct zs_pool *pool, struct size_class *class) +static unsigned long __zs_compact(struct zs_pool *pool, + struct size_class *class) { struct zs_compact_control cc; struct zspage *src_zspage; struct zspage *dst_zspage = NULL; + unsigned long pages_freed = 0; spin_lock(&class->lock); while ((src_zspage = isolate_zspage(class, true))) { @@ -2246,7 +2248,7 @@ static void __zs_compact(struct zs_pool putback_zspage(class, dst_zspage); if (putback_zspage(class, src_zspage) == ZS_EMPTY) { free_zspage(pool, class, src_zspage); - pool->stats.pages_compacted += class->pages_per_zspage; + pages_freed += class->pages_per_zspage; } spin_unlock(&class->lock); cond_resched(); @@ -2257,12 +2259,15 @@ static void __zs_compact(struct zs_pool putback_zspage(class, src_zspage); spin_unlock(&class->lock); + + return pages_freed; } unsigned long zs_compact(struct zs_pool *pool) { int i; struct size_class *class; + unsigned long pages_freed = 0; for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) { class = pool->size_class[i]; @@ -2270,10 +2275,11 @@ unsigned long zs_compact(struct zs_pool continue; if (class->index != i) continue; - __zs_compact(pool, class); + pages_freed += __zs_compact(pool, class); } + atomic_long_add(pages_freed, &pool->stats.pages_compacted); - return pool->stats.pages_compacted; + return pages_freed; } EXPORT_SYMBOL_GPL(zs_compact); @@ -2290,13 +2296,12 @@ static unsigned long zs_shrinker_scan(st struct zs_pool *pool = container_of(shrinker, struct zs_pool, shrinker); - pages_freed = pool->stats.pages_compacted; /* * Compact classes and calculate compaction delta. * Can run concurrently with a manually triggered * (by user) compaction. */ - pages_freed = zs_compact(pool) - pages_freed; + pages_freed = zs_compact(pool); return pages_freed ? pages_freed : SHRINK_STOP; }