From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7CFD5C4332F for ; Thu, 2 Nov 2023 02:48:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235201AbjKBCss (ORCPT ); Wed, 1 Nov 2023 22:48:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231574AbjKBCsr (ORCPT ); Wed, 1 Nov 2023 22:48:47 -0400 Received: from out-170.mta1.migadu.com (out-170.mta1.migadu.com [95.215.58.170]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6280D8E for ; Wed, 1 Nov 2023 19:48:41 -0700 (PDT) Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1698893319; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kchOEnv+0+G+NTW2ZTXj19K8ovH9eGO5OxgkkLRBKSc=; b=s3TDnI7NaTzsW5+1iIijs5G+fJJjdXby6MT2LJOvjPjIVlcKzEVEwIjZd5Q9tC2k5Vofn7 luHa3KYhVXZ/wGRAx8/pcgiJj3WYKgqWAXfDOTePM56UBpJEdDLQlSbe3wJfNtDPtfbjvI UJPZ8YE7YSeIlEthD2kYj34DgLsU5NU= Date: Thu, 2 Nov 2023 10:48:10 +0800 MIME-Version: 1.0 Subject: Re: [RFC PATCH v4 9/9] slub: Update frozen slabs documentations in the source Content-Language: en-US To: Vlastimil Babka , cl@linux.com, penberg@kernel.org, willy@infradead.org Cc: rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Chengming Zhou References: <20231031140741.79387-1-chengming.zhou@linux.dev> <20231031140741.79387-10-chengming.zhou@linux.dev> <211ac705-5972-9b39-73f1-a608e65b6de3@suse.cz> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: <211ac705-5972-9b39-73f1-a608e65b6de3@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/11/1 21:51, Vlastimil Babka wrote: > On 10/31/23 15:07, chengming.zhou@linux.dev wrote: >> From: Chengming Zhou >> >> The current updated scheme (which this series implemented) is: >> - node partial slabs: PG_Workingset && !frozen >> - cpu partial slabs: !PG_Workingset && !frozen >> - cpu slabs: !PG_Workingset && frozen >> - full slabs: !PG_Workingset && !frozen > > It could be useful to put this also to the initial comment description. > Towards the end of the comment, there's a block explaining > "slab->frozen". It could be extended to cover all 4 combination (but not > all of them need such long explanation). > Ok, I will extend it and put in the cover letter of v5. >> >> The most important change is that "frozen" bit is not set for the >> cpu partial slabs anymore, __slab_free() will grab node list_lock >> then check by !PG_Workingset that it's not on a node partial list. >> >> And the "frozen" bit is still kept for the cpu slabs for performance, >> since we don't need to grab node list_lock to check whether the >> PG_Workingset is set or not if the "frozen" bit is set in __slab_free(). >> >> Update related documentations and comments in the source. >> >> Signed-off-by: Chengming Zhou >> --- >> mm/slub.c | 16 ++++++++++++---- >> 1 file changed, 12 insertions(+), 4 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index bb7368047103..89d3f7a18a73 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -76,13 +76,22 @@ >> * >> * Frozen slabs >> * >> - * If a slab is frozen then it is exempt from list management. It is not >> - * on any list except per cpu partial list. The processor that froze the >> + * If a slab is frozen then it is exempt from list management. It is >> + * the cpu slab which is actively allocated from by the processor that >> + * froze it and it is not on any list. The processor that froze the >> * slab is the one who can perform list operations on the slab. Other >> * processors may put objects onto the freelist but the processor that >> * froze the slab is the only one that can retrieve the objects from the >> * slab's freelist. >> * >> + * CPU partial slabs >> + * >> + * The partially empty slabs cached on the CPU partial list are used >> + * for performance reasons, which speeds up the allocation process. >> + * These slabs are not frozen, but also exempt from list management, > > ^ are also > > (otherwise somebody could read it as "also are not") > Ah, will fix. Thanks!