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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7E3DFC6FD1C for ; Thu, 23 Mar 2023 08:04:50 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 12008900003; Thu, 23 Mar 2023 04:04:50 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0D08D900002; Thu, 23 Mar 2023 04:04:50 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F00F3900003; Thu, 23 Mar 2023 04:04:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id E0B72900002 for ; Thu, 23 Mar 2023 04:04:49 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id AD1B11C4E91 for ; Thu, 23 Mar 2023 08:04:49 +0000 (UTC) X-FDA: 80599426698.23.704101E Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf02.hostedemail.com (Postfix) with ESMTP id CAC978000C for ; Thu, 23 Mar 2023 08:04:47 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=none; dmarc=none; spf=none (imf02.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1679558688; h=from:from:sender: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: in-reply-to:in-reply-to:references:references; bh=mevmzcRW5raKRxRMUQm8jlYDge96hF8uqwcMTBFv9NY=; b=xQoG0KQBjPL/Qo2qNFprNXr4KTKPfkQziT8PGOoFJEvaK5YIBukmSaw5/TkWsZuT67C6Us qVYcYulLR8efu5351BS3ZaR5Di9u0lKAjn/1nTZjkYbUe0z4u2I3CEvdhjyapRNy4MBDc5 y8PzYk/bRIAQJmBFItVOx4CshBM111s= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=none; dmarc=none; spf=none (imf02.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1679558688; a=rsa-sha256; cv=none; b=qjBkSAF1kfncRr+b+foC5qHhtDacrfEqP7w8FcaovectlH3Pt2wfPlVL0Qv3IE6DNwDUuU r+1PYzM9yyUPINZGOLcOrrXrbUmDu+n+P79J2gvnqIx8XQdDDULgzxYe7ju2LEhDZfSmUd YKPXWxVx7X4G8k20fm5/ELHgb/ee9iM= Received: by verein.lst.de (Postfix, from userid 2407) id C6BB968B05; Thu, 23 Mar 2023 09:04:43 +0100 (CET) Date: Thu, 23 Mar 2023 09:04:43 +0100 From: Christoph Hellwig To: Liu Shixin Cc: Seth Jennings , Dan Streetman , Vitaly Wool , Andrew Morton , Nathan Chancellor , Christoph Hellwig , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH -next v6 2/2] mm/zswap: delay the initializaton of zswap Message-ID: <20230323080443.GC20444@lst.de> References: <20230322102006.780624-1-liushixin2@huawei.com> <20230322102006.780624-3-liushixin2@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230322102006.780624-3-liushixin2@huawei.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: CAC978000C X-Stat-Signature: 1zj1ttniuo9m8a3i1zm16j46eajeam8e X-Rspam-User: X-HE-Tag: 1679558687-395381 X-HE-Meta: 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 3s6rWrxj J9HT1DQ0Ge90SPwTKp9A3fU9+0mOs2GsQR6CJgW6NHflVO06MXWsxx9YI9xTd8H1+cNrUeXvvf9z9L31W2lTSF6un5eqkw2MBDudj X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Mar 22, 2023 at 06:20:06PM +0800, Liu Shixin wrote: > Since some users may not use zswap, the zswap_pool is wasted. Save memory > by delaying the initialization of zswap until enabled. > > Signed-off-by: Liu Shixin > --- > mm/zswap.c | 51 +++++++++++++++++++++++++++++++++++++++++---------- > 1 file changed, 41 insertions(+), 10 deletions(-) > > diff --git a/mm/zswap.c b/mm/zswap.c > index 09fa956920fa..3aed3b26524a 100644 > --- a/mm/zswap.c > +++ b/mm/zswap.c > @@ -81,6 +81,8 @@ static bool zswap_pool_reached_full; > > #define ZSWAP_PARAM_UNSET "" > > +static int zswap_setup(void); > + > /* Enable/disable zswap */ > static bool zswap_enabled = IS_ENABLED(CONFIG_ZSWAP_DEFAULT_ON); > static int zswap_enabled_param_set(const char *, > @@ -220,6 +222,9 @@ static bool zswap_init_started; > /* fatal error during init */ > static bool zswap_init_failed; > > +/* used to ensure the integrity of initialization */ > +static DEFINE_MUTEX(zswap_init_lock); > + > /* init completed, but couldn't create the initial pool */ > static bool zswap_has_pool; > > @@ -272,13 +277,13 @@ static void zswap_update_total_size(void) > **********************************/ > static struct kmem_cache *zswap_entry_cache; > > -static int __init zswap_entry_cache_create(void) > +static int zswap_entry_cache_create(void) > { > zswap_entry_cache = KMEM_CACHE(zswap_entry, 0); > return zswap_entry_cache == NULL; > } Please add a cleanup patch to remove this helper first, it just massivel confuses the reader. > -static void __init zswap_entry_cache_destroy(void) > +static void zswap_entry_cache_destroy(void) > { > kmem_cache_destroy(zswap_entry_cache); > } Same here. > @@ -663,7 +668,7 @@ static struct zswap_pool *zswap_pool_create(char *type, char *compressor) > return NULL; > } > > -static __init struct zswap_pool *__zswap_pool_create_fallback(void) > +static struct zswap_pool *__zswap_pool_create_fallback(void) > { > bool has_comp, has_zpool; > > @@ -784,8 +789,15 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp, > /* if this is load-time (pre-init) param setting, > * don't create a pool; that's done during init. > */ > - if (!zswap_init_started) > - return param_set_charp(s, kp); > + if (!zswap_init_started) { > + mutex_lock(&zswap_init_lock); > + if (!zswap_init_started) { > + ret = param_set_charp(s, kp); > + mutex_unlock(&zswap_init_lock); > + return ret; > + } > + mutex_unlock(&zswap_init_lock); > + } Just take the lock around the whole function. No need to micro-optimize setting a kernel paramter. > @@ -884,6 +896,15 @@ static int zswap_enabled_param_set(const char *val, > if (res == *(bool *)kp->arg) > return 0; > > + if (!zswap_init_started && (system_state == SYSTEM_RUNNING)) { No need for the inner braces. But directly looking at SYSTEM_RUNNING, especially without a comment is a bit of a mess. Is there any better way to deal with this? Also the zswap_init_started variable name has always been a bit confusing. If everything around it takes zswap_init_lock now, it can be replaced with a check for successful zswap initialization as all the initializtion is covered by the lock. That would really help to clean up the code. > +static int zswap_debugfs_init(void) > { > if (!debugfs_initialized()) > return -ENODEV; > @@ -1482,7 +1503,7 @@ static int __init zswap_debugfs_init(void) > return 0; > } > #else > -static int __init zswap_debugfs_init(void) > +static int zswap_debugfs_init(void) Is there any reason to not just always initialize debugfs and only defer the expensive allocations?