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[49.181.60.96]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3039dff0529sm2964573a91.16.2025.03.27.13.22.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 27 Mar 2025 13:22:48 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.98) (envelope-from ) id 1txtkT-000000016eh-2SQ3; Fri, 28 Mar 2025 07:22:45 +1100 Date: Fri, 28 Mar 2025 07:22:45 +1100 From: Dave Chinner To: Jan Kara Cc: Luis Chamberlain , patches@lists.linux.dev, fstests@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, oliver.sang@intel.com, hannes@cmpxchg.org, willy@infradead.org, apopple@nvidia.com, brauner@kernel.org, hare@suse.de, oe-lkp@lists.linux.dev, lkp@intel.com, john.g.garry@oracle.com, p.raghav@samsung.com, da.gomez@samsung.com, dave@stgolabs.net, riel@surriel.com, krisman@suse.de, boris@bur.io, jackmanb@google.com, gost.dev@samsung.com Subject: Re: [PATCH] generic/764: fsstress + migrate_pages() test Message-ID: References: <20250326185101.2237319-1-mcgrof@kernel.org> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Mar 27, 2025 at 12:53:30PM +0100, Jan Kara wrote: > On Wed 26-03-25 11:50:55, Luis Chamberlain wrote: > > 0-day reported a page migration kernel warning with folios which happen > > to be buffer-heads [0]. I'm having a terribly hard time reproducing the bug > > and so I wrote this test to force page migration filesystems. > > > > It turns out we have have no tests for page migration on fstests or ltp, > > and its no surprise, other than compaction covered by generic/750 there > > is no easy way to trigger page migration right now unless you have a > > numa system. > > > > We should evaluate if we want to help stress test page migration > > artificially by later implementing a way to do page migration on simple > > systems to an artificial target. > > > > So far, this doesn't trigger any kernel splats, not even warnings for me. > > > > Reported-by: kernel test robot > > Link: https://lore.kernel.org/r/202503101536.27099c77-lkp@intel.com # [0] > > Signed-off-by: Luis Chamberlain > > So when I was testing page migration in the past MM guys advised me to use > THP compaction as a way to trigger page migration. You can manually > trigger compaction by: > > echo 1 >/proc/sys/vm/compact_memory Right, that's what generic/750 does. IT runs fsstress and every 5 seconds runs memory compaction in the background. > So you first mess with the page cache a bit to fragment memory and then > call the above to try to compact it back... Which is effectively what g/750 tries to exercise. When it's run by check-parallel, compaction ends up doing a lot more work over a much wider range of tests... -Dave. -- Dave Chinner david@fromorbit.com