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Tue, 18 Feb 2025 22:35:54 -0500 X-MC-Unique: U_QZBFe5OUKPyV0XMEpg5A-1 X-Mimecast-MFC-AGG-ID: U_QZBFe5OUKPyV0XMEpg5A_1739936153 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5A9D71800877; Wed, 19 Feb 2025 03:35:52 +0000 (UTC) Received: from localhost (unknown [10.72.112.127]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 9F4081800359; Wed, 19 Feb 2025 03:35:50 +0000 (UTC) Date: Wed, 19 Feb 2025 11:35:46 +0800 From: Baoquan He To: Kairui Song Cc: linux-mm@kvack.org, Andrew Morton , Chris Li , Barry Song , Hugh Dickins , Yosry Ahmed , "Huang, Ying" , Nhat Pham , Johannes Weiner , Kalesh Singh , linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/7] mm, swap: avoid redundant swap device pinning Message-ID: References: <20250214175709.76029-1-ryncsn@gmail.com> <20250214175709.76029-4-ryncsn@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250214175709.76029-4-ryncsn@gmail.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Rspam-User: X-Rspamd-Queue-Id: EF0798000B X-Rspamd-Server: rspam07 X-Stat-Signature: iqyc9xiypndipqiohqipo4q7nyud3e9i X-HE-Tag: 1739936159-981788 X-HE-Meta: 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 dXr3Kqs/ jTm1f0DWA27YRoOS55HuObfJwM0eJxxgBk36p4L8d6DW9FpjK4gtpWhp2tU3eFO/ZkbQyCd0qzD4OX67JX+yXTC8GfmPclPaKkWngq+Rf/cH3wCMvI+XBzH7MPQ+hFT4BkT3b1fA7mCikDxPtybuPfwOcOVYtBJ+SebY3x4JTnXRlo8ycCuXu8Vb+wYjPaKoBP8llKRKgDKs45j5uIMQ+hXBvN71eL9O1shtGUP+0jKF6kgTQBpZZDVHsoT9svxBq1G8vzcbWa2N6ICjKMgmW2+hHxd8I2FDjBn47X2WFKroKYACbl23tM6o8jHl6qUXRA42YFvgFTaD4M1j49JrK3FxlBdNBcfx4V5OdPuOWTu6EMb8WJlX30LuzMxEbo3KJ58E2S+OqdJMQKDh2EkPYUDUR8DBR7MGAqlcvYITNMhh4L8CuL8z/1Gdnun6oqLNTGfK1 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 02/15/25 at 01:57am, Kairui Song wrote: > From: Kairui Song > > There are only two callers of __read_swap_cache_async not holding a swap > device reference, so make them hold a reference instead, and drop the > get/put_swap_device calls in __read_swap_cache_async. This should reduce > the overhead for swap in during page fault slightly. This looks good to me, while the log makes me take a little longer time to understand. Maybe rephrasing them a little bit can facilitate the log reading. Not sure if my understanding is correct. ======= Currently, __read_swap_cache_async() has get/put_swap_device() calls to increase/decrease a swap device reference. While some of its callers have held the swap device reference, e.g in do_swap_page() and shmem_swapin_folio() where __read_swap_cache_async() will finally called. Now there are only two excpetional callers not holding a swap device reference, so make them hold a reference instead. And drop the get/put_swap_device calls in __read_swap_cache_async. This should reduce the overhead for swap in during page fault slightly. ======== Other than the nit in log, this looks good to me. Reviewed-by: Baoquan He > > Signed-off-by: Kairui Song > --- > mm/swap_state.c | 14 ++++++++------ > mm/zswap.c | 6 ++++++ > 2 files changed, 14 insertions(+), 6 deletions(-) > > diff --git a/mm/swap_state.c b/mm/swap_state.c > index a54b035d6a6c..50840a2887a5 100644 > --- a/mm/swap_state.c > +++ b/mm/swap_state.c > @@ -426,17 +426,13 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > struct mempolicy *mpol, pgoff_t ilx, bool *new_page_allocated, > bool skip_if_exists) > { > - struct swap_info_struct *si; > + struct swap_info_struct *si = swp_swap_info(entry); > struct folio *folio; > struct folio *new_folio = NULL; > struct folio *result = NULL; > void *shadow = NULL; > > *new_page_allocated = false; > - si = get_swap_device(entry); > - if (!si) > - return NULL; > - > for (;;) { > int err; > /* > @@ -532,7 +528,6 @@ struct folio *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > put_swap_folio(new_folio, entry); > folio_unlock(new_folio); > put_and_return: > - put_swap_device(si); > if (!(*new_page_allocated) && new_folio) > folio_put(new_folio); > return result; > @@ -552,11 +547,16 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > struct vm_area_struct *vma, unsigned long addr, > struct swap_iocb **plug) > { > + struct swap_info_struct *si; > bool page_allocated; > struct mempolicy *mpol; > pgoff_t ilx; > struct folio *folio; > > + si = get_swap_device(entry); > + if (!si) > + return NULL; > + > mpol = get_vma_policy(vma, addr, 0, &ilx); > folio = __read_swap_cache_async(entry, gfp_mask, mpol, ilx, > &page_allocated, false); > @@ -564,6 +564,8 @@ struct folio *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask, > > if (page_allocated) > swap_read_folio(folio, plug); > + > + put_swap_device(si); > return folio; > } > > diff --git a/mm/zswap.c b/mm/zswap.c > index ac9d299e7d0c..83dfa1f9e689 100644 > --- a/mm/zswap.c > +++ b/mm/zswap.c > @@ -1051,14 +1051,20 @@ static int zswap_writeback_entry(struct zswap_entry *entry, > struct folio *folio; > struct mempolicy *mpol; > bool folio_was_allocated; > + struct swap_info_struct *si; > struct writeback_control wbc = { > .sync_mode = WB_SYNC_NONE, > }; > > /* try to allocate swap cache folio */ > + si = get_swap_device(swpentry); > + if (!si) > + return -EEXIST; > + > mpol = get_task_policy(current); > folio = __read_swap_cache_async(swpentry, GFP_KERNEL, mpol, > NO_INTERLEAVE_INDEX, &folio_was_allocated, true); > + put_swap_device(si); > if (!folio) > return -ENOMEM; > > -- > 2.48.1 >