From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D83211703 for ; Mon, 21 Aug 2023 19:59:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69D03C433C7; Mon, 21 Aug 2023 19:59:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692647951; bh=iWDUk4P8sKQkD6Cjm9oKNbn77WdQ3tBoUc1YZyoI8eE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VHdEt55ca4r0pdeUVX7clmNe4XoMKCJetQMkrA9h3W7Q46C8dpPH/OP3FFIY455dA HrpHLu1YHr131kx0M+wi6IVNeBeeKKS1U5mzP+jfKtRdw2QaI3QEey+cVDZDIaf6w/ JLFpQZG8GuDYmKM3rywh2u4UzLUBXGOso8q1vhEA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sergey Senozhatsky , Yosry Ahmed , Minchan Kim , Andrew Morton Subject: [PATCH 6.1 167/194] zsmalloc: allow only one active pool compaction context Date: Mon, 21 Aug 2023 21:42:26 +0200 Message-ID: <20230821194130.043557852@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230821194122.695845670@linuxfoundation.org> References: <20230821194122.695845670@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Sergey Senozhatsky commit d2658f2052c7db6ec0a79977205f8cf1cb9effc2 upstream. zsmalloc pool can be compacted concurrently by many contexts, e.g. cc1 handle_mm_fault() do_anonymous_page() __alloc_pages_slowpath() try_to_free_pages() do_try_to_free_pages( lru_gen_shrink_node() shrink_slab() do_shrink_slab() zs_shrinker_scan() zs_compact() Pool compaction is currently (basically) single-threaded as it is performed under pool->lock. Having multiple compaction threads results in unnecessary contention, as each thread competes for pool->lock. This, in turn, affects all zsmalloc operations such as zs_malloc(), zs_map_object(), zs_free(), etc. Introduce the pool->compaction_in_progress atomic variable, which ensures that only one compaction context can run at a time. This reduces overall pool->lock contention in (corner) cases when many contexts attempt to shrink zspool simultaneously. Link: https://lkml.kernel.org/r/20230418074639.1903197-1-senozhatsky@chromium.org Fixes: c0547d0b6a4b ("zsmalloc: consolidate zs_pool's migrate_lock and size_class's locks") Signed-off-by: Sergey Senozhatsky Reviewed-by: Yosry Ahmed Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/zsmalloc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -246,6 +246,7 @@ struct zs_pool { struct work_struct free_work; #endif spinlock_t lock; + atomic_t compaction_in_progress; }; struct zspage { @@ -2100,6 +2101,15 @@ unsigned long zs_compact(struct zs_pool struct size_class *class; unsigned long pages_freed = 0; + /* + * Pool compaction is performed under pool->lock so it is basically + * single-threaded. Having more than one thread in __zs_compact() + * will increase pool->lock contention, which will impact other + * zsmalloc operations that need pool->lock. + */ + if (atomic_xchg(&pool->compaction_in_progress, 1)) + return 0; + for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) { class = pool->size_class[i]; if (class->index != i) @@ -2107,6 +2117,7 @@ unsigned long zs_compact(struct zs_pool pages_freed += __zs_compact(pool, class); } atomic_long_add(pages_freed, &pool->stats.pages_compacted); + atomic_set(&pool->compaction_in_progress, 0); return pages_freed; } @@ -2193,6 +2204,7 @@ struct zs_pool *zs_create_pool(const cha init_deferred_free(pool); spin_lock_init(&pool->lock); + atomic_set(&pool->compaction_in_progress, 0); pool->name = kstrdup(name, GFP_KERNEL); if (!pool->name)