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s=arc-20220608; d=hostedemail.com; t=1712845839; a=rsa-sha256; cv=none; b=hkCdV3RQIvWK+5j1GUQ6OWqMdiFcaFk22baIamaWxxu4/7ZTBQKvTlzZIDQGrXUwCYfTcG QIBJBNycOKmNpTYpW+D0Abz1/l/mKrhtGeyRFe71JrBHKqDnb5LSUFA4CKhz1m30+8haR0 OsfRbQkgDw+eTpIGI2ncAIBAg+vMnD8= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=none; spf=pass (imf23.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9D1AC339; Thu, 11 Apr 2024 07:31:07 -0700 (PDT) Received: from [10.1.38.151] (XHFQ2J9959.cambridge.arm.com [10.1.38.151]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D55BC3F64C; Thu, 11 Apr 2024 07:30:35 -0700 (PDT) Message-ID: <95bc0ebb-49f4-4331-8809-3e4625f1d91a@arm.com> Date: Thu, 11 Apr 2024 15:30:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] mm: swap: introduce swap_free_nr() for batched swap_free() Content-Language: en-GB To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: 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 References: <20240409082631.187483-1-21cnbao@gmail.com> <20240409082631.187483-2-21cnbao@gmail.com> From: Ryan Roberts In-Reply-To: <20240409082631.187483-2-21cnbao@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 3E5FF14002A X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: gn9bq8e1ad4ircmxhmb48jsmy6ee6qa7 X-HE-Tag: 1712845839-270775 X-HE-Meta: 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 heFuO8Az II9EYwk7pTi0XLiIGGAHcXsDuiEvOoTIFCBGsWnJWKOGsnhc/2THP8vx/iE4MteF2SuAvtqm4YATwYNq4su7cwZcysj3NVq+3Y6lG4bYBUXI3+52IplILwrFkPETg+FhcL556N0ahjBq/0nsccrD9EvE7y/Xkwm1nmAyT12V4hPKt4cKObtgF68BD8fepy1Adcm+uaC7xpqxTVDN83ECNQo8f/2XwifD8cMlwcwPoRB0aL4SR0XGzEuJNh6aOsA39yffZsWzjwKx5iuF9B+uPBTdiFyQF8VzlBnj2YXZDmN2Svhl6Zyi0MUw8rdodEAgxTiLY 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: 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 whole > folio. To avoid frequently acquiring and releasing swap locks, it is better > 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 = swp_type(entry); > + unsigned long offset = swp_offset(entry); > + int batch_nr, remain_nr; > + DECLARE_BITMAP(usage, SWAP_BATCH_NR) = { 0 }; > + > + /* all swap entries are within a cluster for mTHP */ > + VM_BUG_ON(offset % SWAPFILE_CLUSTER + nr_pages > SWAPFILE_CLUSTER); > + > + if (nr_pages == 1) { > + swap_free(entry); > + return; > + } > + > + remain_nr = nr_pages; > + p = _swap_info_get(entry); > + if (p) { nit: perhaps return early if (!p) ? Then you dedent the for() block. > + for (i = 0; i < nr_pages; i += batch_nr) { > + batch_nr = min_t(int, SWAP_BATCH_NR, remain_nr); > + > + ci = lock_cluster_or_swap_info(p, offset); > + for (j = 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 += batch_nr; if (i < nr_pages) break; > + bitmap_clear(usage, 0, SWAP_BATCH_NR); > + remain_nr -= batch_nr; > + } > + } > +} > + > /* > * Called after dropping swapcache to decrease refcnt to swap entries. > */