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Thu, 11 Apr 2024 19:07:47 -0700 (PDT) MIME-Version: 1.0 References: <20240409082631.187483-1-21cnbao@gmail.com> <20240409082631.187483-2-21cnbao@gmail.com> <95bc0ebb-49f4-4331-8809-3e4625f1d91a@arm.com> In-Reply-To: <95bc0ebb-49f4-4331-8809-3e4625f1d91a@arm.com> From: Chuanhua Han Date: Fri, 12 Apr 2024 10:07:35 +0800 Message-ID: Subject: Re: [PATCH v2 1/5] mm: swap: introduce swap_free_nr() for batched swap_free() To: Ryan Roberts Cc: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, chrisl@kernel.org, david@redhat.com, hanchuanhua@oppo.com, hannes@cmpxchg.org, hughd@google.com, kasong@tencent.com, surenb@google.com, v-songbaohua@oppo.com, willy@infradead.org, xiang@kernel.org, ying.huang@intel.com, yosryahmed@google.com, yuzhao@google.com, ziy@nvidia.com, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 66B1A40002 X-Rspam-User: X-Stat-Signature: ucwhuoq5w3wm9cxwdczbwujfn17q35hg X-Rspamd-Server: rspam01 X-HE-Tag: 1712887669-636464 X-HE-Meta: U2FsdGVkX19HGHshq1Xme/KP3MV16FsQwTROIGibJSlK0ksVUNPkbJHAPSh9KcZOGefmMoJbPaX5hslKHDu24f7S0O0TWAOWvoVcr6L5A5XFQeu90EAAoChoiVLoaSWdARJdFMNjPlGBp8IqkncXUYFNbCUGR4I9LLLJDglyTwatlt6iWMdmrbHYgwwvJ/M44fTUMcg0jXx7sGkU0c6c4VPil7VABvJtKKLf14C8dZf/OzpI02rrlgCKgI4NvSn7TNYg5Ztn8FBL2h+r502gECeHq1aXDAYWnmaIRjC66SZ9j0Hzi+UZ3EL1RMOrQlnLtaQJ2gZu4PU3hWn+oPFbb3SEPNiqu/kyls49vjmPEOXZL4b3C/Y2njbte8lyg9arxwE/2r2CgS8pDVZg4sDiEdJPS3ak+sfRmFt9C49fhkCJFheZ8nb6y63NP2iwbZzESxoGnPLfgT54vLCezeHNIIyaCf0CGlVVshkfFGvzZX9+42np2iF6r/bhsWWCeOn6P4cnIylQW3JeKfx2f6KkvE5cOin72oQ/q58F94k2Vzurkb+XTEhte+QOPPvDTr2kKuIlLHNfqphPO/JWeoT/8egp9Ec6V4p2Fg3taXPeWDm5LzKj53qMk7877cW89NsNvWnQ2/V+maH73LZirvHG9Hhs+5OK1mZ2//uD0r1tJq0My5pWO/EdFlInGZ7+iLjQzMlrAmZ+VIT8vf0q+oZgIZG5l+oFkPHF0dr/03E5dqbJpmoL12pVc+5aGP5qcez9Ug7z218VyHlKgLPR0MFnfegFZEMHsMtWoxsSs+kwKd574eeAjGN+/PR8xdFCcDMzN/DGVUD8kG+TczLNYVadd/ZPBwc71ULREso6wgyXp7NP61+6YPWs6NnRctC7AwN5hRrwVYv7mpjeydPDrFnXWxqBRgB/mCsyjUm/rfEXJ3iUktZ4WsPgc3JFHDzSlCqx79euThRECO0ifBPes02 6+LV9b04 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Ryan Roberts =E4=BA=8E2024=E5=B9=B44=E6=9C=8811=E6= =97=A5=E5=91=A8=E5=9B=9B 22:30=E5=86=99=E9=81=93=EF=BC=9A > > On 09/04/2024 09:26, Barry Song wrote: > > From: Chuanhua Han > > > > While swapping in a large folio, we need to free swaps related to the w= hole > > folio. To avoid frequently acquiring and releasing swap locks, it is be= tter > > to introduce an API for batched free. > > > > Signed-off-by: Chuanhua Han > > Co-developed-by: Barry Song > > Signed-off-by: Barry Song > > Couple of nits; feel free to ignore. > > Reviewed-by: Ryan Roberts > > > --- > > include/linux/swap.h | 5 +++++ > > mm/swapfile.c | 51 ++++++++++++++++++++++++++++++++++++++++++++ > > 2 files changed, 56 insertions(+) > > > > diff --git a/include/linux/swap.h b/include/linux/swap.h > > index 11c53692f65f..b7a107e983b8 100644 > > --- a/include/linux/swap.h > > +++ b/include/linux/swap.h > > @@ -483,6 +483,7 @@ extern void swap_shmem_alloc(swp_entry_t); > > extern int swap_duplicate(swp_entry_t); > > extern int swapcache_prepare(swp_entry_t); > > extern void swap_free(swp_entry_t); > > +extern void swap_free_nr(swp_entry_t entry, int nr_pages); > > extern void swapcache_free_entries(swp_entry_t *entries, int n); > > extern void free_swap_and_cache_nr(swp_entry_t entry, int nr); > > int swap_type_of(dev_t device, sector_t offset); > > @@ -564,6 +565,10 @@ static inline void swap_free(swp_entry_t swp) > > { > > } > > > > +void swap_free_nr(swp_entry_t entry, int nr_pages) > > +{ > > +} > > + > > static inline void put_swap_folio(struct folio *folio, swp_entry_t swp= ) > > { > > } > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 28642c188c93..f4c65aeb088d 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -1356,6 +1356,57 @@ void swap_free(swp_entry_t entry) > > __swap_entry_free(p, entry); > > } > > > > +/* > > + * Free up the maximum number of swap entries at once to limit the > > + * maximum kernel stack usage. > > + */ > > +#define SWAP_BATCH_NR (SWAPFILE_CLUSTER > 512 ? 512 : SWAPFILE_CLUSTER= ) > > + > > +/* > > + * Called after swapping in a large folio, batched free swap entries > > + * for this large folio, entry should be for the first subpage and > > + * its offset is aligned with nr_pages > > + */ > > +void swap_free_nr(swp_entry_t entry, int nr_pages) > > +{ > > + int i, j; > > + struct swap_cluster_info *ci; > > + struct swap_info_struct *p; > > + unsigned int type =3D swp_type(entry); > > + unsigned long offset =3D swp_offset(entry); > > + int batch_nr, remain_nr; > > + DECLARE_BITMAP(usage, SWAP_BATCH_NR) =3D { 0 }; > > + > > + /* all swap entries are within a cluster for mTHP */ > > + VM_BUG_ON(offset % SWAPFILE_CLUSTER + nr_pages > SWAPFILE_CLUSTER= ); > > + > > + if (nr_pages =3D=3D 1) { > > + swap_free(entry); > > + return; > > + } > > + > > + remain_nr =3D nr_pages; > > + p =3D _swap_info_get(entry); > > + if (p) { > > nit: perhaps return early if (!p) ? Then you dedent the for() block. Agreed! > > > + for (i =3D 0; i < nr_pages; i +=3D batch_nr) { > > + batch_nr =3D min_t(int, SWAP_BATCH_NR, remain_nr)= ; > > + > > + ci =3D lock_cluster_or_swap_info(p, offset); > > + for (j =3D 0; j < batch_nr; j++) { > > + if (__swap_entry_free_locked(p, offset + = i * SWAP_BATCH_NR + j, 1)) > > + __bitmap_set(usage, j, 1); > > + } > > + unlock_cluster_or_swap_info(p, ci); > > + > > + for_each_clear_bit(j, usage, batch_nr) > > + free_swap_slot(swp_entry(type, offset + i= * SWAP_BATCH_NR + j)); > > + > > nit: perhaps change to for (;;), and do the checks here to avoid clearing= the > bitmap on the last run: > > i +=3D batch_nr; > if (i < nr_pages) > break; Great, thank you for your advice! > > > + bitmap_clear(usage, 0, SWAP_BATCH_NR); > > + remain_nr -=3D batch_nr; > > + } > > + } > > +} > > + > > /* > > * Called after dropping swapcache to decrease refcnt to swap entries. > > */ > > --=20 Thanks, Chuanhua