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[90.233.216.238]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-52ca28722b0sm1286680e87.126.2024.06.17.10.19.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Jun 2024 10:19:56 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 17 Jun 2024 19:19:53 +0200 To: "Jason A. Donenfeld" Cc: Uladzislau Rezki , "Paul E. McKenney" , Vlastimil Babka , Jakub Kicinski , Julia Lawall , linux-block@vger.kernel.org, kernel-janitors@vger.kernel.org, bridge@lists.linux.dev, linux-trace-kernel@vger.kernel.org, Mathieu Desnoyers , kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "Naveen N. Rao" , Christophe Leroy , Nicholas Piggin , netdev@vger.kernel.org, wireguard@lists.zx2c4.com, linux-kernel@vger.kernel.org, ecryptfs@vger.kernel.org, Neil Brown , Olga Kornievskaia , Dai Ngo , Tom Talpey , linux-nfs@vger.kernel.org, linux-can@vger.kernel.org, Lai Jiangshan , netfilter-devel@vger.kernel.org, coreteam@netfilter.org Subject: Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple kmem_cache_free callback Message-ID: References: Precedence: bulk X-Mailing-List: bridge@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Jun 17, 2024 at 06:57:45PM +0200, Jason A. Donenfeld wrote: > On Mon, Jun 17, 2024 at 06:42:23PM +0200, Uladzislau Rezki wrote: > > On Mon, Jun 17, 2024 at 06:33:23PM +0200, Jason A. Donenfeld wrote: > > > On Mon, Jun 17, 2024 at 6:30 PM Uladzislau Rezki wrote: > > > > Here if an "err" is less then "0" means there are still objects > > > > whereas "is_destroyed" is set to "true" which is not correlated > > > > with a comment: > > > > > > > > "Destruction happens when no objects" > > > > > > The comment is just poorly written. But the logic of the code is right. > > > > > OK. > > > > > > > > > > > out_unlock: > > > > > mutex_unlock(&slab_mutex); > > > > > cpus_read_unlock(); > > > > > diff --git a/mm/slub.c b/mm/slub.c > > > > > index 1373ac365a46..7db8fe90a323 100644 > > > > > --- a/mm/slub.c > > > > > +++ b/mm/slub.c > > > > > @@ -4510,6 +4510,8 @@ void kmem_cache_free(struct kmem_cache *s, void *x) > > > > > return; > > > > > trace_kmem_cache_free(_RET_IP_, x, s); > > > > > slab_free(s, virt_to_slab(x), x, _RET_IP_); > > > > > + if (s->is_destroyed) > > > > > + kmem_cache_destroy(s); > > > > > Here i am not follow you. How do you see that a cache has been fully > > freed? Or is it just super draft code? > > kmem_cache_destroy() does this in shutdown_cache(). > Right. In this scenario you invoke kmem_cache_destroy() over and over until the last object gets freed. This potentially slowing the kmem_cache_free() which is not OK, at least to me. -- Uladzislau Rezki 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 354C4C27C79 for ; Mon, 17 Jun 2024 17:20:46 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20230601 header.b=fQDA4cBs; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4W2xVM6fs0z3gFN for ; Tue, 18 Jun 2024 03:20:43 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20230601 header.b=fQDA4cBs; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=gmail.com (client-ip=2a00:1450:4864:20::135; helo=mail-lf1-x135.google.com; envelope-from=urezki@gmail.com; receiver=lists.ozlabs.org) Received: from mail-lf1-x135.google.com (mail-lf1-x135.google.com [IPv6:2a00:1450:4864:20::135]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4W2xTY3jSdz3g6G for ; Tue, 18 Jun 2024 03:20:00 +1000 (AEST) Received: by mail-lf1-x135.google.com with SMTP id 2adb3069b0e04-52c85a7f834so5914334e87.0 for ; Mon, 17 Jun 2024 10:20:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1718644797; x=1719249597; darn=lists.ozlabs.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:date:from:from:to :cc:subject:date:message-id:reply-to; bh=vZ8O3vkKnV5WMsPPzukATAgUwpYfoN3xcCe/8i65jUE=; b=fQDA4cBsNxII6P1cTHgzp6yteqBun6ktKn70VM6Vv2jkecWJY3VNAYxarpNC4b2grx xotYpACGCV0xUJDXWSC1yWQEdrcY8cRHR/clorlYm5CG6kS2DqYop+q/fOge5YnlyNxS AWsFMKo453jLIDoL6WdTf3Pi91dCKTFM4va1inEV/iAQsRHpiDn3ot+/E3GqiIt0eFqp Frq0Q66E5pozM9s85mKFAPiHJ+cI8H0hftYZ9LnXrvaE5yVkwia8eQZVjZiPanLykEqQ WA0dRB61+lKaBOTl/E5UZv8QQ02QScVjfZyDOexrMHFExYv8Er4L/EADciOOrlEGYVMm cP5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1718644797; x=1719249597; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:date:from :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=vZ8O3vkKnV5WMsPPzukATAgUwpYfoN3xcCe/8i65jUE=; b=ItEm0d+r60l6JklCGskOGpxDEoS34C7rVlmsT/PfKVwT77dIiPOw6H3C1BzKxfCiTJ //m53Tnki5Yj0gNVplNjiGOiq8OZ5mSVQBPC0Qn5r4a6g5jawFvR4f0tdAg0iL2rCxqa cCRc+q30slSiYst/ITngTjOJ9mYGcSFJCt46aP25TyJ4sC2q3guybywCunMRuCa4ouUC nQ1FFdzUtmLk3T7c2zpWuQvWHGOwldOVIVy44LIvyiQuGFi1O9oejPMcwKie/fSi3h6R /XnD5DBl4TH2kW9eQ64vO/Yp4enI40teTVH4m0kyFrKPGO7FK1vZVT5vKqCYa6BJ7Moi m48w== X-Forwarded-Encrypted: i=1; AJvYcCUAKTRQOSQar23jgM4WRZ7XrcqsBMoRU0QwLif4modyJOuzEPvo+Eau4dsN6/jJ+X4FjPei6VRBI6WjQ4PCGAUymF6eTUotb4YG7SeXDQ== X-Gm-Message-State: AOJu0YzVznObET6cHNW3GN1ZeOUKeYWVcowABySb1LK06YHh21xyF9C1 iHZiGdAaCjmiVJfpDJP527V6RIqS7yEKzKidNJCXSagD4aLK0sjK X-Google-Smtp-Source: AGHT+IF+kn6orlxXNu+KbBfK5TuJ9FRTaW/E7mKFLwWnfY9/g3N+9lA943ajPi6EK1Z9MmgGKAp4XQ== X-Received: by 2002:a19:8c5a:0:b0:52c:88d6:891d with SMTP id 2adb3069b0e04-52ca6e5637emr6427245e87.9.1718644797253; Mon, 17 Jun 2024 10:19:57 -0700 (PDT) Received: from pc636 (host-90-233-216-238.mobileonline.telia.com. [90.233.216.238]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-52ca28722b0sm1286680e87.126.2024.06.17.10.19.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Jun 2024 10:19:56 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 17 Jun 2024 19:19:53 +0200 To: "Jason A. Donenfeld" Subject: Re: [PATCH 00/14] replace call_rcu by kfree_rcu for simple kmem_cache_free callback Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, Neil Brown , kernel-janitors@vger.kernel.org, Olga Kornievskaia , Dai Ngo , Christophe Leroy , coreteam@netfilter.org, "Naveen N. Rao" , Jakub Kicinski , linux-trace-kernel@vger.kernel.org, "Paul E. McKenney" , bridge@lists.linux.dev, ecryptfs@vger.kernel.org, Nicholas Piggin , linux-can@vger.kernel.org, linux-block@vger.kernel.org, Mathieu Desnoyers , Vlastimil Babka , Tom Talpey , linux-nfs@vger.kernel.org, netdev@vger.kernel.org, Lai Jiangshan , linux-kernel@vger.kernel.org, Julia Lawall , Uladzislau Rezki , netfilter-devel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, wireguard@lists.zx2c4.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Jun 17, 2024 at 06:57:45PM +0200, Jason A. Donenfeld wrote: > On Mon, Jun 17, 2024 at 06:42:23PM +0200, Uladzislau Rezki wrote: > > On Mon, Jun 17, 2024 at 06:33:23PM +0200, Jason A. Donenfeld wrote: > > > On Mon, Jun 17, 2024 at 6:30 PM Uladzislau Rezki wrote: > > > > Here if an "err" is less then "0" means there are still objects > > > > whereas "is_destroyed" is set to "true" which is not correlated > > > > with a comment: > > > > > > > > "Destruction happens when no objects" > > > > > > The comment is just poorly written. But the logic of the code is right. > > > > > OK. > > > > > > > > > > > out_unlock: > > > > > mutex_unlock(&slab_mutex); > > > > > cpus_read_unlock(); > > > > > diff --git a/mm/slub.c b/mm/slub.c > > > > > index 1373ac365a46..7db8fe90a323 100644 > > > > > --- a/mm/slub.c > > > > > +++ b/mm/slub.c > > > > > @@ -4510,6 +4510,8 @@ void kmem_cache_free(struct kmem_cache *s, void *x) > > > > > return; > > > > > trace_kmem_cache_free(_RET_IP_, x, s); > > > > > slab_free(s, virt_to_slab(x), x, _RET_IP_); > > > > > + if (s->is_destroyed) > > > > > + kmem_cache_destroy(s); > > > > > Here i am not follow you. How do you see that a cache has been fully > > freed? Or is it just super draft code? > > kmem_cache_destroy() does this in shutdown_cache(). > Right. In this scenario you invoke kmem_cache_destroy() over and over until the last object gets freed. This potentially slowing the kmem_cache_free() which is not OK, at least to me. -- Uladzislau Rezki