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Mon, 11 Sep 2023 11:16:24 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 11 Sep 2023 20:16:21 +0200 To: Baoquan He Cc: "Uladzislau Rezki (Sony)" , linux-mm@kvack.org, Andrew Morton , LKML , Lorenzo Stoakes , Christoph Hellwig , Matthew Wilcox , "Liam R . Howlett" , Dave Chinner , "Paul E . McKenney" , Joel Fernandes , Oleksiy Avramchenko Subject: Re: [PATCH v2 7/9] mm: vmalloc: Support multiple nodes in vread_iter Message-ID: References: <20230829081142.3619-1-urezki@gmail.com> <20230829081142.3619-8-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 533E240010 X-Stat-Signature: bjwpgyacq9y364sbj7hd6mka14zrmwcb X-Rspam-User: X-HE-Tag: 1694456187-195616 X-HE-Meta: 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 CQpWRXQB 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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: On Mon, Sep 11, 2023 at 11:58:13AM +0800, Baoquan He wrote: > On 08/29/23 at 10:11am, Uladzislau Rezki (Sony) wrote: > > Extend the vread_iter() to be able to perform a sequential > > reading of VAs which are spread among multiple nodes. So a > > data read over the /dev/kmem correctly reflects a vmalloc > > memory layout. > > > > Signed-off-by: Uladzislau Rezki (Sony) > > --- > > mm/vmalloc.c | 67 +++++++++++++++++++++++++++++++++++++++++----------- > > 1 file changed, 53 insertions(+), 14 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 4fd4915c532d..968144c16237 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > ...... > > @@ -4057,19 +4093,15 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count) > > > > remains = count; > > > > - /* Hooked to node_0 so far. */ > > - vn = addr_to_node(0); > > - spin_lock(&vn->busy.lock); > > This could change the vread behaviour a little bit. Before, once we take > vmap_area_lock, the vread will read out the content of snapshot at the > moment. Now, reading out in one node's tree won't disrupt other nodes' > tree accessing. Not sure if this matters when people need access > /proc/kcore, e.g dynamic debugging. > With one big tree you anyway drop the lock after one cycle of reading. As far as i see, kcore.c's read granularity is a PAGE_SIZE. Please correct me if i am wrong. > > And, the reading will be a little slower because each va finding need > iterate all vmap_nodes[]. > Right. It is a bit tough here, because we have multiple nodes which represent zones(address space), i.e. there is an offset between them, it means that, reading fully one tree, will not provide a sequential reading. > > Otherwise, the patch itself looks good to me. > > Reviewed-by: Baoquan He > Applied. Thank you for looking at it! -- Uladzislau Rezki