From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DD45E6F30F for ; Mon, 27 Jan 2025 14:39:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737988751; cv=none; b=c5buLmULmrDM8JiwBX/EWE2PfI87JbcVF4rOxlm7B0hXxfB6bAezPQrEX7FuA/JwMi3WEHrfqU7cEwpdByIrCypogZQ6XXUYQBE96Bby83C+ewNPjusdOyKJPYDkERiE3MEAhNhpJttGJ+VMeEITZap52veOu2LgRaupUcZBdAE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737988751; c=relaxed/simple; bh=p4gLaNHRawYXb54OD27ZHGjc582vr6PGPZj7IZDyCKI=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=U2eC6XwfJn+WsTwEdxDVCUkPDye2w+LmSMe8tK6GtUuS0aUfRqoPS4il9Jz/3ZUc+c5k2ubKDzZxFkC4tX8UY/jk57piQ58/E4p2T+bfnvJCBSjxro3XJiCtOLC3/3TAt9kuAyr2X7+2Z7i9koolap6Z51Ebat4Ukn8zRF6dc7c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xs5LJS0t; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xs5LJS0t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C42F4C4CED2; Mon, 27 Jan 2025 14:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737988751; bh=p4gLaNHRawYXb54OD27ZHGjc582vr6PGPZj7IZDyCKI=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Xs5LJS0twt7azjVGRQDZEq3gTPfrSwk0EyMwRr6dfEaAp+cqp/351N9zhsg1CC/+z GIkZIA/dp2riG1k/zCNKRSIIXRkT+BlGY0jDszajAkZVP5HjhubwUKwCjYqO3hNsXS wtBqVNaR8xNvWzoGkHlXMYn6gldjiIUM4DUjiu8AeZcOzTkxzBcUOhzY6QKdvIsdT6 3Gh/bjjMbNkTkilMu6r+a28uwqzNy8M2554VceMn5qMYNeY8U0xLaUanN2s6Pjsx5n 47cn+5+NFRUx69cm7F/DI6DI7Apsfg/3epB+lNCHFuUerCja7ZLf+bb10spoGoiu1x 0v3SNOmzOFWxA== Message-ID: <7735374ea376d966042160332bb8e9012a54187e.camel@kernel.org> Subject: Re: [PATCH 6/7] nfsd: filecache: change garbage collection to a timer. From: Jeff Layton To: NeilBrown , Chuck Lever Cc: linux-nfs@vger.kernel.org, Olga Kornievskaia , Dai Ngo , Tom Talpey , Dave Chinner Date: Mon, 27 Jan 2025 09:39:09 -0500 In-Reply-To: <20250127012257.1803314-7-neilb@suse.de> References: <20250127012257.1803314-1-neilb@suse.de> <20250127012257.1803314-7-neilb@suse.de> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ 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CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-01-27 at 12:20 +1100, NeilBrown wrote: > garbage collection never sleeps and no longer walks a list so it runs > quickly only requiring a spinlock. >=20 > This means we don't need to use a workqueue, we can use a simple timer > instead. >=20 > Rather than taking the lock in the timer callback, which would require > using _bh locking, simply test a flag and wake an nfsd thread. That > thread checks the flag and ages the lists when needed. >=20 > Signed-off-by: NeilBrown > --- > fs/nfsd/filecache.c | 43 ++++++++++++++++++++++++------------------- > 1 file changed, 24 insertions(+), 19 deletions(-) >=20 > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > index 7264faa57280..eb95a53f806f 100644 > --- a/fs/nfsd/filecache.c > +++ b/fs/nfsd/filecache.c > @@ -67,10 +67,12 @@ struct nfsd_fcache_disposal { > struct list_head older; /* haven't been used in last 0-2 seconds */ > struct list_head freeme; /* ready to be discarded */ > unsigned long num_gc; /* Approximate size of recent plus older */ Dang, adding flags would push this into=20 > - struct delayed_work filecache_laundrette; > + struct timer_list timer; > struct shrinker *file_shrinker; > struct nfsd_net *nn; > + unsigned long flags; > }; > +#define NFSD_FCACHE_DO_AGE BIT(0) /* time to age the lists */ > =20 > static struct kmem_cache *nfsd_file_slab; > static struct kmem_cache *nfsd_file_mark_slab; > @@ -115,8 +117,8 @@ static const struct rhashtable_params nfsd_file_rhash= _params =3D { > static void > nfsd_file_schedule_laundrette(struct nfsd_fcache_disposal *l) > { > - queue_delayed_work(system_unbound_wq, &l->filecache_laundrette, > - NFSD_LAUNDRETTE_DELAY); > + if (!timer_pending(&l->timer)) > + mod_timer(&l->timer, jiffies + NFSD_LAUNDRETTE_DELAY); > } > =20 > static void > @@ -521,6 +523,19 @@ void nfsd_file_net_dispose(struct nfsd_net *nn) > { > struct nfsd_fcache_disposal *l =3D nn->fcache_disposal; > =20 > + if (test_and_clear_bit(NFSD_FCACHE_DO_AGE, &l->flags)) { > + spin_lock(&l->lock); > + list_splice_init(&l->older, &l->freeme); > + list_splice_init(&l->recent, &l->older); > + /* We don't know how many were moved to 'freeme' and don't want > + * to waste time counting - guess a half. This is only used > + * for the shrinker which doesn't need complete precision. > + */ > + l->num_gc /=3D 2; > + if (!list_empty(&l->older) || !list_empty(&l->recent)) > + mod_timer(&l->timer, jiffies + NFSD_LAUNDRETTE_DELAY); > + spin_unlock(&l->lock); > + } > if (!list_empty(&l->freeme)) { > LIST_HEAD(dispose); > int i; > @@ -557,23 +572,13 @@ void nfsd_file_net_dispose(struct nfsd_net *nn) > } > =20 > static void > -nfsd_file_gc_worker(struct work_struct *work) > +nfsd_file_gc_worker(struct timer_list *t) > { > struct nfsd_fcache_disposal *l =3D container_of( > - work, struct nfsd_fcache_disposal, filecache_laundrette.work); > + t, struct nfsd_fcache_disposal, timer); > =20 > - spin_lock(&l->lock); > - list_splice_init(&l->older, &l->freeme); > - list_splice_init(&l->recent, &l->older); > - /* We don't know how many were moved to 'freeme' and don't want > - * to waste time counting - guess a half. > - */ > - l->num_gc /=3D 2; > - if (!list_empty(&l->freeme)) > - svc_wake_up(l->nn->nfsd_serv); > - if (!list_empty(&l->older) || !list_empty(&l->recent)) > - nfsd_file_schedule_laundrette(l); > - spin_unlock(&l->lock); > + set_bit(NFSD_FCACHE_DO_AGE, &l->flags); > + svc_wake_up(l->nn->nfsd_serv); Disregard my earlier comment about the cacheline. It still wouldn't hurt to do, but since you're not actually taking the lock inside the timer callback in this version, it's not as big a deal. This seems better. > } > =20 > static unsigned long > @@ -868,7 +873,7 @@ nfsd_alloc_fcache_disposal(void) > if (!l) > return NULL; > spin_lock_init(&l->lock); > - INIT_DELAYED_WORK(&l->filecache_laundrette, nfsd_file_gc_worker); > + timer_setup(&l->timer, nfsd_file_gc_worker, 0); > INIT_LIST_HEAD(&l->recent); > INIT_LIST_HEAD(&l->older); > INIT_LIST_HEAD(&l->freeme); > @@ -891,7 +896,7 @@ nfsd_alloc_fcache_disposal(void) > static void > nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l) > { > - cancel_delayed_work_sync(&l->filecache_laundrette); > + del_timer_sync(&l->timer); > shrinker_free(l->file_shrinker); > nfsd_file_release_list(&l->recent); > WARN_ON_ONCE(!list_empty(&l->recent)); Reviewed-by: Jeff Layton