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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tTKxe-0000000Gopk-18x6; Thu, 02 Jan 2025 13:10:02 +0000 Date: Thu, 2 Jan 2025 13:10:02 +0000 From: Matthew Wilcox To: Baolin Wang Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com, wangkefeng.wang@huawei.com, kasong@tencent.com, ying.huang@linux.alibaba.com, 21cnbao@gmail.com, ryan.roberts@arm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: shmem: skip swapcache for swapin of synchronous swap device Message-ID: References: <04997e54c276eff40a6119a90d36a4e71aade89c.1735806921.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04997e54c276eff40a6119a90d36a4e71aade89c.1735806921.git.baolin.wang@linux.alibaba.com> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: B819040006 X-Stat-Signature: p1ug8ndumitunh7d5uo5qij86wqthybz X-Rspam-User: X-HE-Tag: 1735823364-152428 X-HE-Meta: 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 EHtc+Ioq zmaz0OLtZgtC1V71fgW0eXzqK+z8bwQr+uPHDyXYPzcwOMcVH7/spxwVCCp12gejC26iiZGq8oHPbT9LxvyNoV4fDYzWMhj3qkEqFOF8J1/SIGJVZQNpjrHsyrlNSj0JjbpnslHuum9NFIZ/DDwlG49xuzRfw03Xz2DpGVNqoiKhHjTeJUsBNciBJUh5dZFCpOoyDSCNmrHcpshGANfsbuoD369KIWMFkI76e0CnZgIeq3MI= 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 Thu, Jan 02, 2025 at 04:40:17PM +0800, Baolin Wang wrote: > With fast swap devices (such as zram), swapin latency is crucial to applications. > For shmem swapin, similar to anonymous memory swapin, we can skip the swapcache > operation to improve swapin latency. OK, but now we have more complexity. Why can't we always skip the swapcache on swapin? (Actually, I think we can always skip the swapcache on swapout too, but that's a different matter). > +static struct folio *shmem_swap_alloc_folio(struct inode *inode, struct vm_area_struct *vma, > + pgoff_t index, swp_entry_t entry, int order, gfp_t gfp) Please wrap at 80 columns and use two tabs for indenting subsequent lines. ie: static struct folio *shmem_swap_alloc_folio(struct inode *inode, struct vm_area_struct *vma, pgoff_t index, swp_entry_t entry, int order, gfp_t gfp)