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 53AFA1494CC for ; Wed, 13 Nov 2024 16:48:39 +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=1731516522; cv=none; b=TFoJ0aik/6Wf8ZXqushahRnH+TNGS1FsL7zKGYOaSzwJkMUnbXTcz4OUBswd+cmn51m/EljKUooKNr/4wsI1Z2gRTG7bYJQU0Fbsd+TJCOW6GyPQfcupgJZcNATbVJ/E1b2QpWqiki4QrBVXyy9M5SdgrqGuu73b2o9QkOZzCqo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731516522; c=relaxed/simple; bh=Ttzcmz59EuQuJWgWPnZxmcyEtNf0NBZ/i1YIkBXtQEw=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=IoVYhffl0w68Ev0ibVr9eYKP35/961lNFyVsg2iG5EPofEhVHINtYY+UAkNbNglELcw/gxjvD3WGvsSRWWQiHQpPA88V7cdyoRFxK11dpdLLMgylDAlieB7Vc/rS5W1mVj4nG+XlAUpp95Xpz3HMFWfSRekQBstPQORmahijDdk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xq5pzEcQ; 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="Xq5pzEcQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3B08EC4CECD; Wed, 13 Nov 2024 16:48:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731516519; bh=Ttzcmz59EuQuJWgWPnZxmcyEtNf0NBZ/i1YIkBXtQEw=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Xq5pzEcQqgpFqFWYm7jcWr7tYk71jd83Ha3NacQK7ACtZW81Xa8NcgsVvxewyNDJ4 HghPVYfWTTbYXxo8mJn+7+fgOHax5p45btksxMyY5U7mYhx3ynv5hXNQa7CYSfvKHv SBO5s8JTp0VgY/DtW18GsVscUeCwesXmv4dTDKYQ9jCSDS960uDZMo8AQ77Q7C9AEW Znz6h104zhsniEw0tntZnlkLu/kRSx7ZnPGSZV7ZM8l6g7J3irrGlIcsVQJwqTIIiZ vX1RUdrblwB5/7+5YPiNB1UituZI17sn2SV0tCd9i4Bg6/K6eHFA60LY+rwQJH+Nvu PS3a0iAC5zsDw== Message-ID: <1db227ccb347c7877998ab20a609bc3a9896c7db.camel@kernel.org> Subject: Re: [PATCH 1/4] nfsd: remove artificial limits on the session-based DRC From: Jeff Layton To: NeilBrown , Chuck Lever Cc: linux-nfs@vger.kernel.org, Olga Kornievskaia , Dai Ngo , Tom Talpey Date: Wed, 13 Nov 2024 11:48:38 -0500 In-Reply-To: <20241113055345.494856-2-neilb@suse.de> References: <20241113055345.494856-1-neilb@suse.de> <20241113055345.494856-2-neilb@suse.de> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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space it might be safe to use for the DRC, > simply try allocating slots and be prepared to accept failure. >=20 > The first slot for each session is allocated with GFP_KERNEL which is > unlikely to fail. Subsequent slots are allocated with the addition of > __GFP_NORETRY which is expected to fail if there isn't much free memory. >=20 > This is probably too aggressive but clears the way for adding a > shrinker interface to free extra slots when memory is tight. >=20 > Also *always* allow NFSD_MAX_SLOTS_PER_SESSION slot pointers per > session. This allows the session to be allocated before we know how > many slots we will successfully allocate, and will be useful when we > starting dynamically increasing the number of allocated slots. >=20 > Signed-off-by: NeilBrown > --- > fs/nfsd/nfs4state.c | 91 +++++++-------------------------------------- > fs/nfsd/nfsd.h | 3 -- > fs/nfsd/nfssvc.c | 32 ---------------- > fs/nfsd/state.h | 2 +- > 4 files changed, 14 insertions(+), 114 deletions(-) >=20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 551d2958ec29..2dcba0c83c10 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -1935,59 +1935,6 @@ static inline u32 slot_bytes(struct nfsd4_channel_= attrs *ca) > return size + sizeof(struct nfsd4_slot); > } > =20 > -/* > - * XXX: If we run out of reserved DRC memory we could (up to a point) > - * re-negotiate active sessions and reduce their slot usage to make > - * room for new connections. For now we just fail the create session. > - */ > -static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca, struct nfsd= _net *nn) > -{ > - u32 slotsize =3D slot_bytes(ca); > - u32 num =3D ca->maxreqs; > - unsigned long avail, total_avail; > - unsigned int scale_factor; > - > - spin_lock(&nfsd_drc_lock); > - if (nfsd_drc_max_mem > nfsd_drc_mem_used) > - total_avail =3D nfsd_drc_max_mem - nfsd_drc_mem_used; > - else > - /* We have handed out more space than we chose in > - * set_max_drc() to allow. That isn't really a > - * problem as long as that doesn't make us think we > - * have lots more due to integer overflow. > - */ > - total_avail =3D 0; > - avail =3D min((unsigned long)NFSD_MAX_MEM_PER_SESSION, total_avail); > - /* > - * Never use more than a fraction of the remaining memory, > - * unless it's the only way to give this client a slot. > - * The chosen fraction is either 1/8 or 1/number of threads, > - * whichever is smaller. This ensures there are adequate > - * slots to support multiple clients per thread. > - * Give the client one slot even if that would require > - * over-allocation--it is better than failure. > - */ > - scale_factor =3D max_t(unsigned int, 8, nn->nfsd_serv->sv_nrthreads); > - > - avail =3D clamp_t(unsigned long, avail, slotsize, > - total_avail/scale_factor); > - num =3D min_t(int, num, avail / slotsize); > - num =3D max_t(int, num, 1); > - nfsd_drc_mem_used +=3D num * slotsize; > - spin_unlock(&nfsd_drc_lock); > - > - return num; > -} > - > -static void nfsd4_put_drc_mem(struct nfsd4_channel_attrs *ca) > -{ > - int slotsize =3D slot_bytes(ca); > - > - spin_lock(&nfsd_drc_lock); > - nfsd_drc_mem_used -=3D slotsize * ca->maxreqs; > - spin_unlock(&nfsd_drc_lock); > -} > - > static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *f= attrs, > struct nfsd4_channel_attrs *battrs) > { > @@ -1996,26 +1943,27 @@ static struct nfsd4_session *alloc_session(struct= nfsd4_channel_attrs *fattrs, > struct nfsd4_session *new; > int i; > =20 > - BUILD_BUG_ON(struct_size(new, se_slots, NFSD_MAX_SLOTS_PER_SESSION) > - > PAGE_SIZE); > + BUILD_BUG_ON(sizeof(new) > PAGE_SIZE); > =20 > - new =3D kzalloc(struct_size(new, se_slots, numslots), GFP_KERNEL); > + new =3D kzalloc(sizeof(*new), GFP_KERNEL); > if (!new) > return NULL; > /* allocate each struct nfsd4_slot and data cache in one piece */ > - for (i =3D 0; i < numslots; i++) { > - new->se_slots[i] =3D kzalloc(slotsize, GFP_KERNEL); > + new->se_slots[0] =3D kzalloc(slotsize, GFP_KERNEL); > + if (!new->se_slots[0]) > + goto out_free; > + > + for (i =3D 1; i < numslots; i++) { > + new->se_slots[i] =3D kzalloc(slotsize, GFP_KERNEL | __GFP_NORETRY); > if (!new->se_slots[i]) > - goto out_free; > + break; > } > - > + fattrs->maxreqs =3D i; > memcpy(&new->se_fchannel, fattrs, sizeof(struct nfsd4_channel_attrs)); > memcpy(&new->se_bchannel, battrs, sizeof(struct nfsd4_channel_attrs)); > =20 > return new; > out_free: > - while (i--) > - kfree(new->se_slots[i]); > kfree(new); > return NULL; > } > @@ -2128,7 +2076,6 @@ static void __free_session(struct nfsd4_session *se= s) > static void free_session(struct nfsd4_session *ses) > { > nfsd4_del_conns(ses); > - nfsd4_put_drc_mem(&ses->se_fchannel); > __free_session(ses); > } > =20 > @@ -3748,17 +3695,6 @@ static __be32 check_forechannel_attrs(struct nfsd4= _channel_attrs *ca, struct nfs > ca->maxresp_cached =3D min_t(u32, ca->maxresp_cached, > NFSD_SLOT_CACHE_SIZE + NFSD_MIN_HDR_SEQ_SZ); > ca->maxreqs =3D min_t(u32, ca->maxreqs, NFSD_MAX_SLOTS_PER_SESSION); > - /* > - * Note decreasing slot size below client's request may make it > - * difficult for client to function correctly, whereas > - * decreasing the number of slots will (just?) affect > - * performance. When short on memory we therefore prefer to > - * decrease number of slots instead of their size. Clients that > - * request larger slots than they need will get poor results: > - * Note that we always allow at least one slot, because our > - * accounting is soft and provides no guarantees either way. > - */ > - ca->maxreqs =3D nfsd4_get_drc_mem(ca, nn); > =20 > return nfs_ok; > } > @@ -3836,11 +3772,11 @@ nfsd4_create_session(struct svc_rqst *rqstp, > return status; > status =3D check_backchannel_attrs(&cr_ses->back_channel); > if (status) > - goto out_release_drc_mem; > + goto out_err; > status =3D nfserr_jukebox; > new =3D alloc_session(&cr_ses->fore_channel, &cr_ses->back_channel); > if (!new) > - goto out_release_drc_mem; > + goto out_err; > conn =3D alloc_conn_from_crses(rqstp, cr_ses); > if (!conn) > goto out_free_session; > @@ -3950,8 +3886,7 @@ nfsd4_create_session(struct svc_rqst *rqstp, > expire_client(old); > out_free_session: > __free_session(new); > -out_release_drc_mem: > - nfsd4_put_drc_mem(&cr_ses->fore_channel); > +out_err: > return status; > } > =20 > diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h > index 4b56ba1e8e48..3eb21e63b921 100644 > --- a/fs/nfsd/nfsd.h > +++ b/fs/nfsd/nfsd.h > @@ -88,9 +88,6 @@ struct nfsd_genl_rqstp { > extern struct svc_program nfsd_programs[]; > extern const struct svc_version nfsd_version2, nfsd_version3, nfsd_versi= on4; > extern struct mutex nfsd_mutex; > -extern spinlock_t nfsd_drc_lock; > -extern unsigned long nfsd_drc_max_mem; > -extern unsigned long nfsd_drc_mem_used; > extern atomic_t nfsd_th_cnt; /* number of available threads */ > =20 > extern const struct seq_operations nfs_exports_op; > diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c > index 49e2f32102ab..3dbaefc96608 100644 > --- a/fs/nfsd/nfssvc.c > +++ b/fs/nfsd/nfssvc.c > @@ -70,16 +70,6 @@ static __be32 nfsd_init_request(struct svc_rqst *, > */ > DEFINE_MUTEX(nfsd_mutex); > =20 > -/* > - * nfsd_drc_lock protects nfsd_drc_max_pages and nfsd_drc_pages_used. > - * nfsd_drc_max_pages limits the total amount of memory available for > - * version 4.1 DRC caches. > - * nfsd_drc_pages_used tracks the current version 4.1 DRC memory usage. > - */ > -DEFINE_SPINLOCK(nfsd_drc_lock); > -unsigned long nfsd_drc_max_mem; > -unsigned long nfsd_drc_mem_used; > - > #if IS_ENABLED(CONFIG_NFS_LOCALIO) > static const struct svc_version *localio_versions[] =3D { > [1] =3D &localio_version1, > @@ -575,27 +565,6 @@ void nfsd_reset_versions(struct nfsd_net *nn) > } > } > =20 > -/* > - * Each session guarantees a negotiated per slot memory cache for replie= s > - * which in turn consumes memory beyond the v2/v3/v4.0 server. A dedicat= ed > - * NFSv4.1 server might want to use more memory for a DRC than a machine > - * with mutiple services. > - * > - * Impose a hard limit on the number of pages for the DRC which varies > - * according to the machines free pages. This is of course only a defaul= t. > - * > - * For now this is a #defined shift which could be under admin control > - * in the future. > - */ > -static void set_max_drc(void) > -{ > - #define NFSD_DRC_SIZE_SHIFT 7 > - nfsd_drc_max_mem =3D (nr_free_buffer_pages() > - >> NFSD_DRC_SIZE_SHIFT) * PAGE_SIZE; > - nfsd_drc_mem_used =3D 0; > - dprintk("%s nfsd_drc_max_mem %lu \n", __func__, nfsd_drc_max_mem); > -} > - > static int nfsd_get_default_max_blksize(void) > { > struct sysinfo i; > @@ -678,7 +647,6 @@ int nfsd_create_serv(struct net *net) > nn->nfsd_serv =3D serv; > spin_unlock(&nfsd_notifier_lock); > =20 > - set_max_drc(); > /* check if the notifier is already set */ > if (atomic_inc_return(&nfsd_notifier_refcount) =3D=3D 1) { > register_inetaddr_notifier(&nfsd_inetaddr_notifier); > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > index 35b3564c065f..c052e9eea81b 100644 > --- a/fs/nfsd/state.h > +++ b/fs/nfsd/state.h > @@ -310,7 +310,7 @@ struct nfsd4_session { > struct list_head se_conns; > u32 se_cb_prog; > u32 se_cb_seq_nr; > - struct nfsd4_slot *se_slots[]; /* forward channel slots */ > + struct nfsd4_slot *se_slots[NFSD_MAX_SLOTS_PER_SESSION]; /* forward cha= nnel slots */ > }; > =20 > /* formatted contents of nfs4_sessionid */ I like this patch overall. One thing we could consider is allocating slots aggressively with GFP_KERNEL up to a particular threshold, and then switch to GFP_NOWAIT, but this seems like a reasonable place to start. =20 --=20 Jeff Layton