Message ID | 20231031140741.79387-10-chengming.zhou@linux.dev |
---|---|
State | New |
Headers |
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[2620:137:e000::3:2]) by mx.google.com with ESMTPS id j1-20020a170902da8100b001c60636e426si1063701plx.432.2023.10.31.07.09.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Oct 2023 07:10:00 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2; Authentication-Results: mx.google.com; dkim=pass header.i=@linux.dev header.s=key1 header.b=Y0fRMVJb; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linux.dev Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by agentk.vger.email (Postfix) with ESMTP id 003D68037AA3; Tue, 31 Oct 2023 07:09:57 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at agentk.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236130AbjJaOJp (ORCPT <rfc822;chrisjones.unixmen@gmail.com> + 33 others); Tue, 31 Oct 2023 10:09:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235747AbjJaOJb (ORCPT <rfc822;linux-kernel@vger.kernel.org>); Tue, 31 Oct 2023 10:09:31 -0400 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [IPv6:2001:41d0:203:375::b5]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 26E4019E for <linux-kernel@vger.kernel.org>; Tue, 31 Oct 2023 07:09:25 -0700 (PDT) X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1698761363; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1rWlR4h5g4eDWf2XTzUlOrJLNxfEOq6mT+00ilTz0G0=; b=Y0fRMVJblxItnO7fa29gryhY0OuDSuYpX3u9Ss3dhqwRf1OZ/GJBzbFxGqASfXa3ZkcDEd llhl/Boestl6/Pzbcckw30/f5cm8ZIVtqAPveVEahzHWy0Mm0D45/0Br2r/TLM+w+opTst LbLFwmWZyebAWLmuYs8XzdN4+enFRJY= From: chengming.zhou@linux.dev To: vbabka@suse.cz, 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@linux.dev, Chengming Zhou <zhouchengming@bytedance.com> Subject: [RFC PATCH v4 9/9] slub: Update frozen slabs documentations in the source Date: Tue, 31 Oct 2023 14:07:41 +0000 Message-Id: <20231031140741.79387-10-chengming.zhou@linux.dev> In-Reply-To: <20231031140741.79387-1-chengming.zhou@linux.dev> References: <20231031140741.79387-1-chengming.zhou@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Spam-Status: No, score=-0.9 required=5.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on agentk.vger.email Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (agentk.vger.email [0.0.0.0]); Tue, 31 Oct 2023 07:09:58 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1781280434110941845 X-GMAIL-MSGID: 1781280434110941845 |
Series |
slub: Delay freezing of CPU partial slabs
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Commit Message
Chengming Zhou
Oct. 31, 2023, 2:07 p.m. UTC
From: Chengming Zhou <zhouchengming@bytedance.com> 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 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 <zhouchengming@bytedance.com> --- mm/slub.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
Comments
On 10/31/23 15:07, chengming.zhou@linux.dev wrote: > From: Chengming Zhou <zhouchengming@bytedance.com> > > 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). > > 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 <zhouchengming@bytedance.com> > --- > 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") > + * by clearing the PG_workingset flag when moving out of the node > + * partial list. Please see __slab_free() for more details. > + * > * list_lock > * > * The list_lock protects the partial and full list on each node and > @@ -2620,8 +2629,7 @@ static void put_partials_cpu(struct kmem_cache *s, > } > > /* > - * Put a slab that was just frozen (in __slab_free|get_partial_node) into a > - * partial slab slot if available. > + * Put a slab into a partial slab slot if available. > * > * If we did not find a slot then simply move all the partials to the > * per node partial list.
On 2023/11/1 21:51, Vlastimil Babka wrote: > On 10/31/23 15:07, chengming.zhou@linux.dev wrote: >> From: Chengming Zhou <zhouchengming@bytedance.com> >> >> 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 <zhouchengming@bytedance.com> >> --- >> 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!
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, + * by clearing the PG_workingset flag when moving out of the node + * partial list. Please see __slab_free() for more details. + * * list_lock * * The list_lock protects the partial and full list on each node and @@ -2620,8 +2629,7 @@ static void put_partials_cpu(struct kmem_cache *s, } /* - * Put a slab that was just frozen (in __slab_free|get_partial_node) into a - * partial slab slot if available. + * Put a slab into a partial slab slot if available. * * If we did not find a slot then simply move all the partials to the * per node partial list.