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([2804:14c:482:87bb::1000]) by smtp.gmail.com with ESMTPSA id 7sm12735937qtu.38.2021.06.08.20.09.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Jun 2021 20:09:15 -0700 (PDT) Message-ID: <2501d7b80d76ceb77678ad027ee6761fa8cd0ea3.camel@gmail.com> Subject: Re: [PATCH v2 2/3] powerpc/mm/hash: Avoid multiple HPT resize-ups on memory hotplug From: Leonardo =?ISO-8859-1?Q?Br=E1s?= To: David Gibson Cc: Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Sandipan Das , Mike Rapoport , Andrew Morton , "Aneesh Kumar K.V" , Nicholas Piggin , Nathan Lynch , David Hildenbrand , Scott Cheloha , Laurent Dufour , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Date: Wed, 09 Jun 2021 00:09:45 -0300 In-Reply-To: References: <20210430143607.135005-1-leobras.c@gmail.com> <20210430143607.135005-3-leobras.c@gmail.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2021-06-07 at 15:10 +1000, David Gibson wrote: > On Fri, Apr 30, 2021 at 11:36:08AM -0300, Leonardo Bras wrote: > > Every time a memory hotplug happens, and the memory limit crosses a > > 2^n > > value, it may be necessary to perform HPT resizing-up, which can > > take > > some time (over 100ms in my tests). > > > > It usually is not an issue, but it can take some time if a lot of > > memory > > is added to a guest with little starting memory: > > Adding 256G to a 2GB guest, for example will require 8 HPT resizes. > > > > Perform an HPT resize before memory hotplug, updating HPT to its > > final size (considering a successful hotplug), taking the number of > > HPT resizes to at most one per memory hotplug action. > > > > Signed-off-by: Leonardo Bras > > Reviewed-by: David Gibson Thanks David! > > > --- > >  arch/powerpc/include/asm/book3s/64/hash.h     |  2 ++ > >  arch/powerpc/mm/book3s64/hash_utils.c         | 20 > > +++++++++++++++++++ > >  .../platforms/pseries/hotplug-memory.c        |  9 +++++++++ > >  3 files changed, 31 insertions(+) > > > > diff --git a/arch/powerpc/include/asm/book3s/64/hash.h > > b/arch/powerpc/include/asm/book3s/64/hash.h > > index d959b0195ad9..fad4af8b8543 100644 > > --- a/arch/powerpc/include/asm/book3s/64/hash.h > > +++ b/arch/powerpc/include/asm/book3s/64/hash.h > > @@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long > > start, unsigned long end, > >                                  int nid, pgprot_t prot); > >  int hash__remove_section_mapping(unsigned long start, unsigned > > long end); > >   > > +void hash_batch_expand_prepare(unsigned long newsize); > > + > >  #endif /* !__ASSEMBLY__ */ > >  #endif /* __KERNEL__ */ > >  #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */ > > diff --git a/arch/powerpc/mm/book3s64/hash_utils.c > > b/arch/powerpc/mm/book3s64/hash_utils.c > > index 608e4ed397a9..3fa395b3fe57 100644 > > --- a/arch/powerpc/mm/book3s64/hash_utils.c > > +++ b/arch/powerpc/mm/book3s64/hash_utils.c > > @@ -859,6 +859,26 @@ int hash__remove_section_mapping(unsigned long > > start, unsigned long end) > >   > >         return rc; > >  } > > + > > +void hash_batch_expand_prepare(unsigned long newsize) > > +{ > > +       const u64 starting_size = ppc64_pft_size; > > + > > +       /* > > +        * Resizing-up HPT should never fail, but there are some > > cases system starts with higher > > +        * SHIFT than required, and we go through the funny case of > > resizing HPT down while > > +        * adding memory > > +        */ > > + > > +       while (resize_hpt_for_hotplug(newsize, false) == -ENOSPC) { > > +               newsize *= 2; > > +               pr_warn("Hash collision while resizing HPT\n"); > > + > > +               /* Do not try to resize to the starting size, or > > bigger value */ > > +               if (htab_shift_for_mem_size(newsize) >= > > starting_size) > > +                       break; > > +       } > > +} > >  #endif /* CONFIG_MEMORY_HOTPLUG */ > >   > >  static void __init hash_init_partition_table(phys_addr_t > > hash_table, > > diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c > > b/arch/powerpc/platforms/pseries/hotplug-memory.c > > index 8377f1f7c78e..48b2cfe4ce69 100644 > > --- a/arch/powerpc/platforms/pseries/hotplug-memory.c > > +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c > > @@ -13,6 +13,7 @@ > >  #include > >  #include > >  #include > > +#include > >   > >  #include > >  #include > > @@ -671,6 +672,10 @@ static int dlpar_memory_add_by_count(u32 > > lmbs_to_add) > >         if (lmbs_available < lmbs_to_add) > >                 return -EINVAL; > >   > > +       if (!radix_enabled()) > > +               hash_batch_expand_prepare(memblock_phys_mem_size() > > + > > +                                                lmbs_to_add * > > drmem_lmb_size()); > > + > >         for_each_drmem_lmb(lmb) { > >                 if (lmb->flags & DRCONF_MEM_ASSIGNED) > >                         continue; > > @@ -788,6 +793,10 @@ static int dlpar_memory_add_by_ic(u32 > > lmbs_to_add, u32 drc_index) > >         if (lmbs_available < lmbs_to_add) > >                 return -EINVAL; > >   > > +       if (!radix_enabled()) > > +               hash_batch_expand_prepare(memblock_phys_mem_size() > > + > > +                                         lmbs_to_add * > > drmem_lmb_size()); > > + > >         for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) { > >                 if (lmb->flags & DRCONF_MEM_ASSIGNED) > >                         continue; > > -- > David Gibson                    | I'll have my music baroque, and my > code > david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ > _other_ >                                 | _way_ _around_! > http://www.ozlabs.org/~dgibson