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AJvYcCXP4mDhlJRN4okwNMWS3x2StOhGdqbkhmbl5711FcGLN0paOHvAKssQ0Tgv0f89h2WD/o1LGNYiaBgIAyLvbKhyWW8Cwi1YfylZtg0= X-Gm-Message-State: AOJu0YylyZZ4VHxRRGJLD0CMvyp93wi7cZU7uivZ9sxUl6xm8GfdjCwq 9Ks/XcwCIaA2wFywH72TovCzCyM6GkuxgYYbIZQQ6k5i0BWD1MplW+g2b36FlZ8= X-Google-Smtp-Source: AGHT+IFBmO+K7zL/agidVg2Z92TSxmmwPsuaZhiJ7FdU+invzsnYzP+ED6r48gQMg6agGpkBHJtLpw== X-Received: by 2002:a05:6a21:6e4b:b0:1c3:b106:d293 with SMTP id adf61e73a8af0-1c42287e800mr783432637.3.1721420488617; Fri, 19 Jul 2024 13:21:28 -0700 (PDT) Received: from [192.168.1.116] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-70cff552c39sm1565712b3a.136.2024.07.19.13.21.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 Jul 2024 13:21:27 -0700 (PDT) Message-ID: <173c7d32-2fae-40e4-a1d8-490cee3bba15@kernel.dk> Date: Fri, 19 Jul 2024 14:21:25 -0600 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC] Slow down of LTP tests aiodio_sparse.c and dio_sparse.c in kernel 6.6 To: Petr Vorel Cc: ltp@lists.linux.it, linux-block@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-xfs@vger.kernel.org, fstests@vger.kernel.org, Jan Kara , David Sterba , Filipe Manana , Amir Goldstein , Cyril Hrubis , Andrea Cervesato , Avinesh Kumar References: <20240719174325.GA775414@pevik> <20240719201352.GA782769@pevik> Content-Language: en-US From: Jens Axboe In-Reply-To: <20240719201352.GA782769@pevik> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/19/24 2:13 PM, Petr Vorel wrote: > Hi Jens, all, > >> On 7/19/24 11:43 AM, Petr Vorel wrote: >>> Hi all, > >>> LTP AIO DIO tests aiodio_sparse.c [1] and dio_sparse.c [2] (using [3]) slowed >>> down on kernel 6.6 on Btrfs and XFS, when run with default parameters. These >>> tests create 100 MB sparse file and write zeros (using libaio or O_DIRECT) while >>> 16 other processes reads the buffer and check only zero is there. > >>> Runtime of this particular setup (i.e. 100 MB file) on Btrfs and XFS on the >>> same system slowed down 9x (6.5: ~1 min 6.6: ~9 min). Ext4 is not affected. >>> (Non default parameter creates much smaller file, thus the change is not that >>> obvious). > >>> Because the slowdown has been here for few kernel releases I suppose nobody >>> complained and the test is somehow artificial (nobody uses this in a real world). >>> But still it'd be good to double check the problem. I can bisect a particular >>> commit. > >>> Because 2 filesystems affected, could be "Improve asynchronous iomap DIO >>> performance" [4] block layer change somehow related? > >> No, because that got disabled before release for unrelated reasons. Why >> don't you just bisect it, since you have a simple test case? > > Jens, thanks for info. Sure, I'll bisect next week and report. > > The reason I reported before bisecting is because it wouldn't be the > first time the test was "artificial" and therefore reported problem > was not fixed. If it's a real problem I would expect it would be also > caught by other people or even by fstests. Didn't look at the test cases, so yeah may very well be bogus. But it also may not... And a bisection may help shine some light on that too, outside of just highlighting what commit made it slower. -- Jens Axboe