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 66208C4167B for ; Tue, 31 Oct 2023 11:42:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343987AbjJaLmD (ORCPT ); Tue, 31 Oct 2023 07:42:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343751AbjJaLmB (ORCPT ); Tue, 31 Oct 2023 07:42:01 -0400 Received: from out-180.mta1.migadu.com (out-180.mta1.migadu.com [95.215.58.180]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3BE0E97 for ; Tue, 31 Oct 2023 04:41:55 -0700 (PDT) Message-ID: <057353e0-7000-4fe5-a64c-092001ae3883@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1698752513; 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=V76Lq4/to2avfqg3j/SuDvEqroCLg6n33KMDEeYM7Y8=; b=XJ9H5E4idUHxUYq+YkvPLwK1jcW5HcAqSBHMhQlJPY+Y5N6LAqRNDy1G5mYS3Lz8XkIihY 2Y++ZScfA2T8HG+BfAuGezU8z3EuqNtYg7dePzjAaxFe/ItvvSVXN8blVvzDdid/HNh1z5 aXSdP0iDFo1EhlGnCaSkdrktBYSrdSo= Date: Tue, 31 Oct 2023 19:41:22 +0800 MIME-Version: 1.0 Subject: Re: [RFC PATCH v3 7/7] slub: Optimize deactivate_slab() Content-Language: en-US To: Vlastimil Babka , cl@linux.com, penberg@kernel.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: <20231024093345.3676493-1-chengming.zhou@linux.dev> <20231024093345.3676493-8-chengming.zhou@linux.dev> <9db65a8d-9f0d-e8ab-55e4-4197dfc54032@suse.cz> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Chengming Zhou In-Reply-To: <9db65a8d-9f0d-e8ab-55e4-4197dfc54032@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 2023/10/31 19:15, Vlastimil Babka wrote: > On 10/24/23 11:33, chengming.zhou@linux.dev wrote: >> From: Chengming Zhou >> >> Since the introduce of unfrozen slabs on cpu partial list, we don't >> need to synchronize the slab frozen state under the node list_lock. >> >> The caller of deactivate_slab() and the caller of __slab_free() won't >> manipulate the slab list concurrently. >> >> So we can get node list_lock in the last stage if we really need to >> manipulate the slab list in this path. >> >> Signed-off-by: Chengming Zhou > > Nice simplification! > >> --- >> mm/slub.c | 70 ++++++++++++++++++++----------------------------------- >> 1 file changed, 25 insertions(+), 45 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 486d44421432..64d550e415eb 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -2449,10 +2449,8 @@ static void init_kmem_cache_cpus(struct kmem_cache *s) >> static void deactivate_slab(struct kmem_cache *s, struct slab *slab, >> void *freelist) >> { >> - enum slab_modes { M_NONE, M_PARTIAL, M_FREE, M_FULL_NOLIST }; >> struct kmem_cache_node *n = get_node(s, slab_nid(slab)); >> int free_delta = 0; >> - enum slab_modes mode = M_NONE; >> void *nextfree, *freelist_iter, *freelist_tail; >> int tail = DEACTIVATE_TO_HEAD; >> unsigned long flags = 0; >> @@ -2499,58 +2497,40 @@ static void deactivate_slab(struct kmem_cache *s, struct slab *slab, >> * unfrozen and number of objects in the slab may have changed. >> * Then release lock and retry cmpxchg again. >> */ > > This comment above (including parts not visible here) should be updated as > there is no more list manipulation during unfreeze. Right! > >> -redo: >> - >> - old.freelist = READ_ONCE(slab->freelist); >> - old.counters = READ_ONCE(slab->counters); >> - VM_BUG_ON(!old.frozen); >> - >> - /* Determine target state of the slab */ >> - new.counters = old.counters; >> - if (freelist_tail) { >> - new.inuse -= free_delta; >> - set_freepointer(s, freelist_tail, old.freelist); >> - new.freelist = freelist; >> - } else >> - new.freelist = old.freelist; >> + do { >> + old.freelist = READ_ONCE(slab->freelist); >> + old.counters = READ_ONCE(slab->counters); >> + VM_BUG_ON(!old.frozen); >> + >> + /* Determine target state of the slab */ >> + new.counters = old.counters; >> + new.frozen = 0; >> + if (freelist_tail) { >> + new.inuse -= free_delta; >> + set_freepointer(s, freelist_tail, old.freelist); >> + new.freelist = freelist; >> + } else >> + new.freelist = old.freelist; > > Per coding style we should have the else with { } even if it's one line, to > match the if branch. Since we touch the code that was previously violating > the style, we can fix up. Ok, I will fix all these. Big thanks for your review! > >> >> - new.frozen = 0; >> + } while (!slab_update_freelist(s, slab, >> + old.freelist, old.counters, >> + new.freelist, new.counters, >> + "unfreezing slab")); >> >> + /* >> + * Stage three: Manipulate the slab list based on the updated state. >> + */ >> if (!new.inuse && n->nr_partial >= s->min_partial) { >> - mode = M_FREE; >> + stat(s, DEACTIVATE_EMPTY); >> + discard_slab(s, slab); >> + stat(s, FREE_SLAB); >> } else if (new.freelist) { >> - mode = M_PARTIAL; >> - /* >> - * Taking the spinlock removes the possibility that >> - * acquire_slab() will see a slab that is frozen >> - */ >> spin_lock_irqsave(&n->list_lock, flags); >> - } else { >> - mode = M_FULL_NOLIST; >> - } >> - >> - >> - if (!slab_update_freelist(s, slab, >> - old.freelist, old.counters, >> - new.freelist, new.counters, >> - "unfreezing slab")) { >> - if (mode == M_PARTIAL) >> - spin_unlock_irqrestore(&n->list_lock, flags); >> - goto redo; >> - } >> - >> - >> - if (mode == M_PARTIAL) { >> add_partial(n, slab, tail); >> spin_unlock_irqrestore(&n->list_lock, flags); >> stat(s, tail); >> - } else if (mode == M_FREE) { >> - stat(s, DEACTIVATE_EMPTY); >> - discard_slab(s, slab); >> - stat(s, FREE_SLAB); >> - } else if (mode == M_FULL_NOLIST) { >> + } else >> stat(s, DEACTIVATE_FULL); >> - } > > Same here. > > Thanks! > >> } >> >> #ifdef CONFIG_SLUB_CPU_PARTIAL >