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 E04A336126 for ; Fri, 6 Dec 2024 13:49:22 +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=1733492963; cv=none; b=IlEsSVa9bZa3E7yU0OTmgcTIRloZSrPzI+kHpqn/8EHzQhxc6Mmbj6RKQwpoZPeUmj/QnntkhC2bV7dVfwohBetWcXWe6CyH17x3uLq7/tWACOCqEE05gkxxGXsH+9iBap0sYd9aTN4xrQcLbDoCtBcH2re7aCpGL+6iSxYrOuE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733492963; c=relaxed/simple; bh=73jRODbhoyG9oGhgaz9i3v77Z3nZuzkuI5SKFv9oeSA=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=GOd0HqDrZVAlw6+6CHlVvp82r7SG1B8ZbgB3sjkrkfYAfY2ZJX7Z5xLKS4+S8c8hwETFDpuQWBtxH3gDOqT/bAb9nN0ENJk5LSdWgJnaXrNucs+2F2BELmYQrJALZ6sLP1KoXePoww9QZ50dksiZzWrIULPnagrShYE4i+iQrwY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Nz6VRR4/; 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="Nz6VRR4/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC735C4CED1; Fri, 6 Dec 2024 13:49:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733492962; bh=73jRODbhoyG9oGhgaz9i3v77Z3nZuzkuI5SKFv9oeSA=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Nz6VRR4/JScwv1xAzniYSAX+JfX4NczXlZHvpm83wvkVf8QgtDjYNAxffkD+zl9LM acS0aCA4b9tCIGUnXvf+XWBvk+b0HOcIlkNOGhxBEmyRTuqytLvDNvuK8PrtIkKYkb agWCzGQqUlRpTxszapXtsinLiDrcT2KQP+LZPbFyGKAFWhZghQrmSCQvaY2Xt348Af oeV+4c90WE2NXKRSxujmbH103VMdp8B7V8NixF3p/o73iarx2QrFJ6FxO+TtGtiAd/ 7ifRZitp/khRKHxe7Aqz6fKM1LIElXS709sgpCGRsKSLSS3FhGOWQ3hZBAJ9OroyWc 3b0qJHMEKvZ2A== Message-ID: <88bcf45dd056320171de9442d5d3684a2f37a612.camel@kernel.org> Subject: Re: [PATCH 4/6] nfsd: allocate new session-based DRC slots on demand. From: Jeff Layton To: NeilBrown Cc: Chuck Lever , linux-nfs@vger.kernel.org, Olga Kornievskaia , Dai Ngo , Tom Talpey Date: Fri, 06 Dec 2024 08:49:20 -0500 In-Reply-To: <173344943283.1734440.2066475669031086509@noble.neil.brown.name> References: <>, <911b04ba2e5389f97fdeaac632b8fb8c66da130e.camel@kernel.org> <173344943283.1734440.2066475669031086509@noble.neil.brown.name> 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 3.54.1 (3.54.1-1.fc41app1) 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 12:43 +1100, NeilBrown wrote: > On Fri, 06 Dec 2024, Jeff Layton wrote: > > 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 = nfsd4_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 = nfsd4_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 > > 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 > I think that if we need a tunable, then it is a failure of design. > If?when someone complains we may well need to redesign. I hope we could > avoid a tunable in that design! >=20 I hope so too. > > =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. > > > + */ > >=20 > > 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. >=20 > Maybe. I'm open simple using GFP_NOWAIT both places. > Most often xa_store won't need to allocate anything - it adds slots to > the array in batches (at least I assume it does - anything else would be > inefficient). So it mostly won't matter. > So if seems at all inelegant - let's drop it. >=20 >=20 I'd prefer we drop that part. It probably won't matter much in the long run anyway. >=20 > >=20 > > > + 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 > > --=20 > > Jeff Layton > >=20 > >=20 >=20 --=20 Jeff Layton