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 9639F1BDE6 for ; Fri, 6 Dec 2024 01:04:17 +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=1733447057; cv=none; b=T04RDZdxZcqO8HfC/yMV9FQ8/3cdZ+YKPK3dBaZFkTVZ/NeBldb3t+/IOQ43OHJl1r+6AKcBrM7Xhz3x6w+BjIRZfYBe6exo7D9QFst5KunpPiw3neQtsEGGvPGCD5SoBBpYt6s3MLstYplI2rBe8ACJZNnk9ADMmeZYOsRUMLw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733447057; c=relaxed/simple; bh=dRdJlifrs5F6BsuqTFBT5K/NnJ93yQkKiQdDIozmSZM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=YFUrEm61nDQ8IO8rQw4wFgQV/5QwKoenLuJwDFuHPu/3Kcy99WakrdHANsEtpKiRlFICOcNkjRWaRe2w9J0BUGYTsK5bRIRou23pJsf2rbdd55NeDm4QlNVZG2BR4DtuOzjEolme8l9uCb5obCVvnUalxARlTzqxW8r9/JR0PcI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PmBdFpgR; 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="PmBdFpgR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1F0BC4CED1; Fri, 6 Dec 2024 01:04:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733447057; bh=dRdJlifrs5F6BsuqTFBT5K/NnJ93yQkKiQdDIozmSZM=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=PmBdFpgRAY4Nq30zXqXz0Y9FMWySYECvFMWgtgua9aQQAlitwAEZ/AUEve9HlrGsJ 11S0Ny0i1sjcchVitgaaL0xHvVBXBdTasR85xl0pknYyQ21EvlactZ8qFmArtIsRMh ZGoJXqNoCDJtB5lHwgGhR5qwklJoxE+lnOxRuhc/Veb8yJq4b5m9IuENZuu9NJRL3r 1xYXKA9RNoNIZDgQkou1aXKsz7NSM24eTURkaRNNDB5k50j62DcX9KuY8t2UVo4aQ5 ANPIiDpH6/O36rgla3vxjkSYSQs+5Rc0CHfEKdnfNSZ4a1mr3AC9JG7d6JLNitqkWy 5EshlTWaBS87Q== Message-ID: <911b04ba2e5389f97fdeaac632b8fb8c66da130e.camel@kernel.org> Subject: Re: [PATCH 4/6] nfsd: allocate new session-based DRC slots on demand. From: Jeff Layton To: NeilBrown , Chuck Lever Cc: linux-nfs@vger.kernel.org, Olga Kornievskaia , Dai Ngo , Tom Talpey Date: Thu, 05 Dec 2024 17:04:16 -0800 In-Reply-To: <20241206004829.3497925-5-neilb@suse.de> References: <20241206004829.3497925-1-neilb@suse.de> <20241206004829.3497925-5-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 cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf 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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 3.52.4 (3.52.4-2.fc40) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2024-12-06 at 11:43 +1100, NeilBrown wrote: > If a client ever uses the highest available slot for a given session, > attempt to allocate more slots so there is room for the client to use > them if wanted. GFP_NOWAIT is used so if there is not plenty of > free memory, failure is expected - which is what we want. It also > allows the allocation while holding a spinlock. >=20 > Each time we increase the number of slots by 20% (rounded up). This > allows fairly quick growth while avoiding excessive over-shoot. >=20 > We would expect to stablise with around 10% more slots available than > the client actually uses. >=20 > Signed-off-by: NeilBrown > --- > fs/nfsd/nfs4state.c | 40 +++++++++++++++++++++++++++++++++++----- > 1 file changed, 35 insertions(+), 5 deletions(-) >=20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 67dfc699e411..ec4468ebbd40 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -4235,11 +4235,6 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd= 4_compound_state *cstate, > slot =3D xa_load(&session->se_slots, seq->slotid); > dprintk("%s: slotid %d\n", __func__, seq->slotid); > =20 > - /* We do not negotiate the number of slots yet, so set the > - * maxslots to the session maxreqs which is used to encode > - * sr_highest_slotid and the sr_target_slot id to maxslots */ > - seq->maxslots =3D session->se_fchannel.maxreqs; > - > trace_nfsd_slot_seqid_sequence(clp, seq, slot); > status =3D check_slot_seqid(seq->seqid, slot->sl_seqid, > slot->sl_flags & NFSD4_SLOT_INUSE); > @@ -4289,6 +4284,41 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd= 4_compound_state *cstate, > cstate->session =3D session; > cstate->clp =3D clp; > =20 > + /* > + * If the client ever uses the highest available slot, > + * gently try to allocate another 20%. This allows > + * fairly quick growth without grossly over-shooting what > + * the client might use. > + */ 20% seems like a reasonable place to start, but I do wonder if this might need to be tunable under some workloads. Oh well, we can cross that bridge if/when someone complains. =20 > + if (seq->slotid =3D=3D session->se_fchannel.maxreqs - 1 && > + session->se_fchannel.maxreqs < NFSD_MAX_SLOTS_PER_SESSION) { > + int s =3D session->se_fchannel.maxreqs; > + int cnt =3D DIV_ROUND_UP(s, 5); > + > + do { > + /* > + * GFP_NOWAIT is a low-priority non-blocking > + * allocation which can be used under > + * client_lock and only succeeds if there is > + * plenty of memory. > + * Use GFP_ATOMIC which is higher priority for > + * xa_store() so we are less likely to waste the > + * effort of the first allocation. > + */ I don't know here. Why not just use GFP_NOWAIT for the xa_store too? If we're so memory constrained that that fails, we're probably better off releasing the slot. > + slot =3D kzalloc(slot_bytes(&session->se_fchannel), > + GFP_NOWAIT); > + if (slot && > + !xa_is_err(xa_store(&session->se_slots, s, slot, > + GFP_ATOMIC | __GFP_NOWARN))) { > + s +=3D 1; > + session->se_fchannel.maxreqs =3D s; > + } else { > + kfree(slot); > + } > + } while (slot && --cnt > 0); > + } > + seq->maxslots =3D session->se_fchannel.maxreqs; > + > out: > switch (clp->cl_cb_state) { > case NFSD4_CB_DOWN: --=20 Jeff Layton